Research activity information

• 2010 北海道開発協会長賞


• 2006 Award on the United Nations Atlas Book


• 2005 Gledden Senior Fellowship Award


• 1998 平成9年度水工学論文奨励賞


• 1998 平成10年度水文水資源学会ポスター賞


• 1995 平成7年度土木学会年次学術講演会優秀講演者賞

• Validity of theoretical solutions for a rotating rectangular basin with two-layer stratification due to a suddenly imposed wind

  Hiroki Matsumoto, Keisuke Nakayama

  Mar. 2025, Physics of Fluids

  Scientific journal


• A Simple Neural Network for Estimating Fine Sediment Sources Using XRF and XRD

  Selline Mutiso, Keisuke Nakayama, Katsuaki Komai

  Nov. 2024, Hydrology

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Effects of rotation on internal solitary waves

  Keisuke Nakayama, Kento Tashita, Tetsuya Shintani

  Aug. 2024, Applied Ocean Research

  Scientific journal


• Quantification of Mixing Depth Using the Gradient Richardson Number in Submerged Aquatic Vegetation Meadows

  H. Matsumoto, K. Nakayama

  Abstract Upper layer thickness (mixing depth) is an essential parameter for estimating the dissolved inorganic carbon and carbon flux at the water surface based on their association with the vertical flux of dissolved inorganic carbon. Previous studies quantified the mixing depth without SAV meadow or penetration depth in the SAV meadow without stratification and wind stress. However, mixing depth related to interaction with submerged aquatic vegetations (SAVs), stratification, and wind stress has yet to be quantified in the previous studies. Our study is the first to quantify the theoretical mixing depth with SAVs according to wind stress, SAV height, and drag coefficient. Theoretical mixing depth was quantified from modeled vertical temperature profile, vertical profile of horizontal velocity, and gradient Richardson number (Ri_g,veg). We found that mixing depth at a Ri_g,veg of 100 demonstrated good agreement with numerical results on average, with the mixing depth estimated in this study (h_{U,this study}) showing high applicability to observations at Komuke Lagoon. Moreover, h_{U,this study} increased with the increasing wind stress and decreasing drag coefficient and SAV height. Further, we found that SAV meadows with stratification and wind stress could be divided into four hydrodynamic regimes: non‐vegetated layers, upper vegetated layers, thermoclines, and benthic boundary layers. Our findings help us estimate mixing depth or vertical flux without complicated numerical simulation and understand flow interaction with SAV, wind stress, and stratification.

  American Geophysical Union (AGU), Jul. 2024, Water Resources Research, 60(8) (8)

  Scientific journal


• Sea ice and waves in the Sea of Okhotsk from 1989 to 2012

  Yukinobu Sato, Keisuke Nakayama, Kazutaka Tateyama, Katsuaki Komai

  Jul. 2024, Cold Regions Science and Technology, 223, English

  [Refereed]

  Scientific journal


• Effects of Different Turbulence Models on Prediction of Oscillating Hydraulic Jump at a Drop Structure with a Trench

  Hideto Yoshimura, Ichiro Fujita, Keisuke Nakayama, Satoshi Yokojima

  Mar. 2024, KSCE Journal of Civil Engineering

  Scientific journal


• Conceptual models of dissolved carbon fluxes in a two-layer stratified lake: interannual typhoon responses under extreme climates

  Hao-Chi Lin, Keisuke Nakayama, Jeng-Wei Tsai, Chih-Yu Chiu

  Oct. 2023, Biogeosciences

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Ideal water temperature environment for giant Marimo (Aegagropila linnaei) in Lake Akan, Japan

  Keisuke Nakayama, Katsuaki Komai, Motoshi Amano, Shintarou Horii, Yuichiro Somiya, Etsuko Kumamoto, Yoichi Oyama

  AbstractAegagropila linnaei is a filamentous green algal species that often forms beautiful spherical shapes called "lake balls" or "Marimo". A. linnaei were once globally distributed around the world, but the population has been declining for several decades. Lake Akan, in Japan, is now the only lake in the world with a colony of giant Marimo (over 20 cm in diameter). Here we show the net growth rate of Marino resulting from photosynthesis and decomposition based on laboratory experiments, MRI analysis, and quantitative element analysis, which show the decomposition rate, the maximum annual Marimo diametric growth rate, and the carbon-to-nitrogen ratio, respectively. We found an explicit dependence of the decomposition rate of Marimo on the cumulative water temperature, with a threshold of 7 °C. MRI analysis showed a high correlation among a Marimo's diameter, surface thickness, and annual diametric growth rate. Moreover, the C/N ratio was high in the exterior side of the surface thickness, indicating that this layer is the main growth area for photosynthesis. These results suggest that the central cavity and the surface thickness represent the change in the growth environment such as water temperature and light intensity. Between the 1980s and the present, Between the 1980s and the present, the cumulative water temperature has increased from about 1250 to about 1600 °C-days. Therefore, the maximum surface thickness has decreased by approximately 1 cm, as estimated by water temperature records and annual diametric growth rates10. As a measure to preserve preferable conditions for colonies of giant Marimo in the face of global warming, the flow of low-temperature river water into Marimo colonies should be protected.

  Oct. 2023, Scientific Reports, English

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Carbon dioxide uptake in a eutrophic stratified reservoir: Freshwater carbon sequestration potential

  Jinichi Sakaguchi, Keisuke Nakayama, Katsuaki Komai, Atsushi Kubo, Taketoshi Shimizu, Junpei Omori, Kohji Uno, Tomoyasu Fujii

  Oct. 2023, Heliyon

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Editorial: Carbon dynamics in freshwater, coastal and oceanic ecosystems in response to the SDG goals

  Jeng-Wei Tsai, Keisuke Nakayama

  Jun. 2023, Frontiers in Marine Science

  Scientific journal


• Numerical analysis of breather interactions

  Keisuke Nakayama, Kevin Lamb

  May 2023


• Coriolis effects on wind-driven upwelling in enclosed basins

  Wataru Ito, Keisuke Nakayama, Tetsuya Shintani

  Mar. 2023, Continental Shelf Research

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Effect of dissolved oxygen on methane production from bottom sediment in a eutrophic stratified lake

  Yasuyuki Maruya, Keisuke Nakayama, Masafumi Sasaki, Katsuaki Komai

  Elsevier BV, Mar. 2023, Journal of Environmental Sciences, 125, 61 - 72

  Scientific journal


• Breather interactions in a three-layer fluid

  K. Nakayama, K.G. Lamb

  Feb. 2023, Journal of Fluid Mechanics

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• A Detailed Analysis on Hydrodynamic Response of a Highly Stratified Lake to Spatio-Temporally Varying Wind Field

  Hieu Ngoc Le, Tetsuya Shintani, Keisuke Nakayama

  Feb. 2023, Water

  Scientific journal


• A Spatially Integrated Dissolved Inorganic Carbon (SiDIC) Model for Aquatic Ecosystems Considering Submerged Vegetation

  K. Nagatomo, K. Nakayama, K. Komai, H. Matsumoto, K. Watanabe, A. Kubo, K. Tada, Y. Maruya, S. Yano, J. W. Tsai, H. C. Lin, M. Vilas, M. R. Hipsey

  Feb. 2023, Journal of Geophysical Research: Biogeosciences, e2022JG007032, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Perceptions of practitioners on the importance and achievement of research and social implementation activities on marine and freshwater carbon

  Satoshi Watanabe, Yasuyuki Maruya, Shinichiro Yano, Keisuke Nakayama

  Research and social implementation related to carbon in marine and freshwater ecosystems are increasingly gaining emphasis in the global quest to achieve carbon neutrality. It is important not only to advance academic research, but also to solve practical problems for improved understanding, maintenance, and dissemination of information on carbon in marine or freshwater areas. In this study, we conducted a questionnaire survey of participants in activities related to carbon in marine or freshwater areas in Japan to clarify which issues were considered important and their understanding of the degree to which activities related to carbon in marine or freshwater areas had been achieved. Based on the responses to all questions, 77.9% of respondents, on average, among the practitioners in marine areas recognized the importance of the program strongly, while 46.5% recognized that the degree of achievement was insufficient. This tendency was more pronounced for carbon in freshwater than in marine areas(72.2% and 48.6%, respectively). The results, grouped by respondent attributes, revealed that the perception of importance and level of achievement varied depending on the organization of the activity, age, and years of knowledge of carbon in marine and/or freshwater areas. Practitioners with greater experience and those working on specific implementations perceived implementation-related aspects as more important and less accomplished than academic ones. This study provides valuable insights into the research aspects of carbon in marine and/or freshwater areas to achieve carbon neutrality.

  Frontiers Media SA, Jan. 2023, Frontiers in Marine Science, 9

  Scientific journal


• EVALUATION OF THE IMPACT OF IMPROVEMENT OF FLOW LEVEES ON THE WATER QUALITY ENVIRONMENT IN LAKE KOMUKE

  SATO Yukinobu, NAKAYAMA Keisuke, KOMAI Katsuaki, SANO Fumiya

  Lake Komuke, which faces the Sea of Okhotsk in Hokkaido, has improved its environment since it became a permanent lake mouth after constructing a flow levee in the Showa 50s. However, although the flow levee built in the Showa 50s is ageing and is undergoing renewal, the width of the mouth may change when the flow levee is improved or renewed, and the change in the width of the mouth may affect the environment inside the lake. Therefore, in this study, we evaluated the influence of changes in the width of the mouth of the lake, focusing on salinity and the amount of dissolved inorganic carbon on the lake environment as water quality items that affect the lake environment using the three-dimensional environmental fluid model Fantom. As a result, we proposed a construction method using existing sheet piles that can improve the flow embankment and channel revetment without changing the width of the mouth of the lake.

  Japan Society of Civil Engineers, 2023, Japanese Journal of JSCE, 79(18) (18), n/a, Japanese


• ESTIMATING ANNUAL CARBON DIOXIDE SEQUESTRATION USING THE EQUATION OF DIC METABOLISM

  MARUYAMA Momoka, NAKAYAMA Keisuke, SHIMIZU Taketoshi, KOMAI Katsuaki

  Recently, it has been revealed that coastal areas and lakes and mashes play a role in absorbing carbon dioxide, suggesting the necessity of establishing a carbon credit approach for the freshwater carbon system. We proposed and verified a new method for estimating carbon dioxide sequestration and reduction using the equation of DIC metabolism (DIC equation). The proposed method has the advantage of considering only vegetation density and length, indicating its potential for use as a new method. The estimated annual sequestration of carbon dioxide by eelgrass in Komuke Lagoon, located in Hokkaido, Japan, using the DIC equation was 1.41 tonnes CO₂ ha-1 year-1, which is close to the value estimated value obtained from the carbon content of eelgrass in Komuke Lagoon and also the estimated value obtained by leaf marking methods in Lake Akkeshi, located in Hokkaido, Japan.

  Japan Society of Civil Engineers, 2023, Japanese Journal of JSCE, 79(18) (18), n/a, Japanese

  Link to Kobe Univ. Repository (Kernel)


• Influence of patch size on hydrodynamic flow in submerged aquatic vegetation

  K. Matsumura, K. Nakayama, H. Matsumoto

  Blue carbon, or carbon dioxide captured and stored by submerged aquatic vegetation (SAV) in ecosystems, has been attracting attention as a measure to mitigate climate change. Since the scale of SAV meadows is smaller than that of topography length scale, with the former often occurring in patches, the flexibilities of SAV motion induce complicated interactions with water flows and make it difficult to estimate carbon sequestration rates. Therefore, this study aims to clarify the influences of SAV patches on water flows and mass transport using laboratory experiments and numerical simulations. An SAV model was successfully applied to analyze the results of laboratory experiments, revealing good agreement and showing that the size of an SAV patch significantly affects the water flows. The extent to which the patch occupies the channel width was revealed to be the most substantial factor in controlling carbon absorption by SAV, and deflection was found to be another significant factor. Implementing global warming countermeasures is a critical goal of climate change mitigation, so our study outcome is expected to be helpful for improving and promoting blue carbon as a negative emission strategy.

  Frontiers Media {SA}, Dec. 2022, Frontiers in Marine Science, 9

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• INVESTIGATION OF OBLIQUE BREATHER INTERACTIONS

  Keisuke NAKAYAMA

  Japan Society of Civil Engineers, Dec. 2022, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 78(2) (2), I_643 - I_648

  [Refereed]

  Scientific journal


• DETERMINING THE SOURCE OF SUSPENDED SEDIMENT AT THE DOWNSTREAM END OF THE RIVER BASIN USING STRUCTURAL EQUATION MODELLING

  Selline MUTISO, Tatsuya HIRAMI, Keisuke NAKAYAMA, Katsuaki KOMAI, Kenichiro KOBAYASHI

  Corresponding, Japan Society of Civil Engineers, Dec. 2022, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 78(2) (2), I_919 - I_924

  [Refereed]

  Scientific journal


• Effects of vorticity on solitary waves

  Keisuke Nakayama, Kojiro Tani, Hideto Yoshimura, Ichiro Fujita

  AbstractThe vorticity effect on solitary wave profiles has not been solved experimentally; previous studies theoretically and numerically showed that when a solitary wave progressed in the positive direction, the effective wavelength of a solitary wave with positive vorticity increased. Using laboratory experiments and fully nonlinear numerical simulations, we here show that the effective wavelength is extended more when positive vorticity is given to a progressive wave in the positive direction. We further show that the total energy increases with increasing positive vorticity, demonstrating that a wave with positive vorticity propagates with less attenuation and lasts longer than a solitary wave with no vorticity. We anticipate that our outcomes will provide a starting point for more sophisticated methods to investigate the effect of vorticity on solitary waves in laboratory experiments and numerical simulations.

  Springer Science and Business Media {LLC}, Nov. 2022, Scientific Reports, 12(1) (1), English

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• TRANSFORMATION OF BREATHER OVER A SLOPING BOTTOM

  Kento TASHITA, Keisuke NAKAYAMA, Tetsuya SHINTANI

  Corresponding, Japan Society of Civil Engineers, Nov. 2022, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 78(2) (2), I_367 - I_372

  [Refereed]

  Scientific journal


• Conceptual models of dissolved carbon fluxes considering interannual typhoon responses under extreme climates in a two-layer stratified lake

  Hao-Chi Lin, Keisuke Nakayama, Jeng-Wei Tsai, Chih-Yu Chiu

  Oct. 2022


• Interaction between seawater carbon dioxide dynamics and stratification in shallow coastal waters: A preliminary study based on a weekly validated three-dimensional ecological model

  Bing Xiong, Shinichiro Yano, Katsuaki Komai, Naoki Saito, Hiroto Komori, Baixin Chi, Lin Hao

  Shallow coastal waters (SCWs) have attracted wide attention in recent years due to their strong carbon sequestration capacity. However, the complex carbon dioxide (CO2) dynamics in the water column makes it difficult to estimate the air–water CO2 fluxes (FCO2) accurately. We developed a numerical model of CO2 dynamics in water based on field measurements for a typical stratified semi-enclosed shallow bay: the Yatsushiro Sea, Japan. The developed model showed an excellent ability to reproduce the stratification and CO2 dynamics of the Yatsushiro Sea. Through numerical model simulations, we analyzed the annual CO2 dynamics in the Yatsushiro Sea in 2018. The results show that the effect of stratification on the CO2 dynamics in seawater varies greatly depending on the distance from the estuary and the period. In the estuarine region, stratification manifests itself throughout the year by promoting the maintenance of a high partial pressure of CO2 (pCO2) in surface waters, resulting in surface pCO2 being higher than atmospheric pCO2 for up to 40 days during the flood period (average surface pCO2 of 539.94 µatm). In contrast, in areas farther from the estuary, stratification mainly acts to promote the maintenance of high pCO2 in surface waters during periods of high freshwater influence. Then changes to a lower surface pCO2 before the freshwater influence leads towards complete dissipation. Finally, we estimated the FCO2 of the Yatsushiro Sea in 2018, and the results showed that the Yatsushiro Sea was a sink area for atmospheric CO2 in 2018 (−1.70 mmol/m2/day).

  Frontiers Media {SA}, Oct. 2022, Frontiers in Marine Science, 9

  Scientific journal


• Effects of oyster aquaculture on carbon capture and removal in a tropical mangrove lagoon in southwestern Taiwan

  Keisuke Nakayama, Yuki Kawahara, Yuki Kurimoto, Kazufumi Tada, Hao-Chi Lin, Meng-Chi Hung, Mei-Li Hsueh, Jeng-Wei Tsai

  Elsevier {BV}, Sep. 2022, Science of The Total Environment, 838, 156460 - 156460, English

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Diffusive methane burst during a blue tide, wind-driven event in a meromictic lake

  Masafumi Sasaki, Keisuke Nakayama, Yasuyuki Maruya

  Elsevier {BV}, Jul. 2022, Marine Pollution Bulletin, 180, 113792 - 113792, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• FACTORS CONTROLLING DISSOLVED INORGANIC CARBON IN AN OYSTER FARMING LAGOON

  Yuki KAWAHARA, Yuki KURIMOTO, Jeng-Wei TSAI, Hao-Chi LIN, Hiroki MATSUMOTO, Kazufumi TADA, Keisuke NAKAYAMA

  Corresponding, Japan Society of Civil Engineers, Jun. 2022, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 78(2) (2), I_637 - I_642

  [Refereed]

  Scientific journal


• ASSESSMENT OF SAV COLONY’S IMPACTS ON FLOW USING LABORATORY EXPERIMENTS AND NUMERIC SIMULATIONS

  Keita MATSUMURA, Hiroki MATSUMOTO, Keisuke NAKAYAMA, Kazufumi TADA, Tetsuya SHINTANI, Hideo YOSHIMURA

  Corresponding, Japan Society of Civil Engineers, Jun. 2022, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 78(2) (2), I_853 - I_858

  [Refereed]

  Scientific journal


• The impacts of the hydraulic retention effect and typhoon disturbance on the carbon flux in shallow subtropical mountain lakes

  Hao-Chi Lin, Jeng-Wei Tsai, Kazufumi Tada, Hiroki Matsumoto, Chih-Yu Chiu, Keisuke Nakayama

  Elsevier BV, Jan. 2022, Science of The Total Environment, 803, 150044 - 150044

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• The structure and formation of giant Marimo (Aegagropila linnaei) in Lake Akan, Japan

  Keisuke Nakayama, Katsuaki Komai, Keisuke Ogata, Toshiro Yamada, Yukinobu Sato, Fumiya Sano, Shintarou Horii, Yuichiro Somiya, Etsuko Kumamoto, Yoichi Oyama

  Dec. 2021, Scientific Reports, 11(1) (1), English

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Multiple solitary wave interactions

  Keisuke Nakayama, Hidekazu Tsuji

  Aug. 2021, Physics of Fluids

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Effect of pycnocline thickness on internal solitary wave breaking over a slope

  Keisuke Nakayama, Ryo Iwata, Tetsuya Shintani

  Elsevier {BV}, Jun. 2021, Ocean Engineering, 230(1) (1), 108884 - 108884

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Effect of coastal boundary representation on basin-scale internal waves

  Wataru Ito, Keisuke Nakayama, Tetsuya Shintani

  Informa {UK} Limited, Apr. 2021, Coastal Engineering Journal, 63(2) (2), 1 - 14

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Influence of Thermal Stratification on Seasonal Net Ecosystem Production and Dissolved Inorganic Carbon in a Shallow Subtropical Lake

  Hao‐Chi Lin, Chih‐Yu Chiu, Jeng‐Wei Tsai, Wen‐Cheng Liu, Kazufumi Tada, Keisuke Nakayama

  American Geophysical Union ({AGU}), Apr. 2021, Journal of Geophysical Research: Biogeosciences, 126(4) (4), English

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• NUMERICAL MODELING OF CO₂ DYNAMICS IN SEAWATER CONSIDERING EFFECTS OF FRESHWATER INFLOW IN THE YATSUSHIRO SEA

  KOMORI Hiroto, XIONG Bing, SAITO Naoki, HAO Lin, CHI Baixin, YANO Shinichiro, KOMAI Katsuaki, NAKAYAMA Keisuke

  Regarding the reduction of atmospheric CO₂, the function of CO₂ absorption in coastal areas has been drawing attention. In this study, we developed a numerical model of pCO₂ dynamics considering effects of freshwater inflow based on the results of field observation in the Yatsushiro Sea, to obtain the basic knowledge about CO₂ dynamics in coastal areas. The model was able to reproduce well the tempo-spatial distribution of pCO₂ and the distribution of salinity and water temperature under different stratification conditions. From the results of the hindcast simulation, it was confirmed that the amount of CO₂ absorbed around the estuary fluctuated greatly spatiotemporally with the big flood. Furthermore, the following two effects of the freshwater inflow on the dynamics of CO₂ in the coastal area are confirmed as follows: i) After flooding, CO₂ release can be promoted by the suface freshwater capping; and ii) After mixing of freshwater and seawater, CO₂ absorption can be promoted by photosynthesis due to blooming of phytoplankton in the surface layer.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 77(2) (2), I_847 - I_852, Japanese


• EXPERIMENTAL AND NUMERCAL ANAYSES OF OSCILLATING HYDRAULIC JUMP AT A DROP STRUCTURE WITH A TRENCH

  YAGI Jumpei, MURATA Yoshiyuki, YOSHIMURA Hideto, FUJITA Ichiro, NAKAYAMA Keisuke

  It has been observed that a periodic water surface oscillation ocurrs downstream of a drop structure with a trench at specific hydraulic and geometric conditions. In order to establish a relationship governing the oscillation frequency, a number of experiments using flow visualization and image analysis techniques were conducted. As a result, we proposed a Strauhal number specific to the oscillating hydraulic jump. In addition, a numerical simulations based on SST ��-�� model was executed to successfully simulate time varying oscillating flow comparable to the experiment.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77(2) (2), I_871 - I_876, Japanese


• CLASSIFICATION OF BREATHER BREAKING OVER A UNIFORM SLOPE

  TASHITA Kento, NAKAYAMA Keisuke, SHINTANI Tetsuya

  In lakes and the ocean, pycnocline is formed due to solar radiation and inflow into the coastal area, on which internal waves are generated by external forces, such as wind stress and tide. Internal waves propagate and break over a topographical slope, resulting in the long-term transport of nutrients, methane, carbon, hypoxia, and other water quality components and the deterioration of the ecological system. Internal solitary waves are revealed to have considerable kinetic energy and affect mass transport. Among internal solitary waves, "breather" is found to exist in a three-layer fluid, but the mechanism of the breather breaking over a slope remains unsolved. Thus, this study aims to clarify how breathers deform over the topographical change and break on a uniform slope by using a three-dimensional numerical model. We revealed that the classification for an internal solitary wave breaking is successfully applied to categorize the breaking type of breathers over a slope.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 77(2) (2), I_343 - I_348, Japanese


• EFFECT OF PYCNOCLINE THICKNESS ON INTERNAL SOLITARY WAVE BREAKING OVER A SLOPE AND ITS CLASSIFICATION

  IWATA Ryo, NAKAYAMA Keisuke, SATO Takahiro, SHINTANI Tetsuya

  In a two-layer fluid, when pycnocline thickness is negligible, an internal solitary wave (ISW) breaking over a slope can be categorized into four breaker types: surging, collapsing, plunging, and fission breakers. The latest classification into four breaker types is based on wave slope, bottom slope gradient and an internal Reynolds number. However, it remains unsolved if this classification can categorize the breaking of an ISW under thick pycnocline conditions. This study uses numerical simulations to investigate the applicability of the classification under changing pycnocline thickness. We found that the classification can categorize all breaker types even when pycnocline thickness varies. Additionally, thicker pycnoclines result in more significant energy loss and onshore mass transport energy loss due to ISW breaking.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77(1) (1), 59 - 73, Japanese


• RESPONSE OF SURFACE VELOCITY COEFFICIENT TO LONGITUDINAL BATHYMETRY VARIATION

  HAMADA Takuya, YOSHIMURA Hideto, FUJITA Ichiro, NAKAYAMA Keisuke

  The surface velocity coefficient is the value that converts the surface velocity into the depth-averaged velocity when observing the discharge, and 0.85 is treated as the standard value in Japan. In recent years, surface velocity measurement by STIV is widely used, but only surface flow information can be obtained. Therefore, it is important to properly determine the coefficient when estimating the discharge. In this paper, we focused on the situation where the water depth gradually changes due to the formation of sandbars. We conducted flume experiments to examine the response characteristics of the surface velocity and the surface velocity coefficient caused by changes in the riverbed slope. As a result, it was shown that the change of the correction coefficient is not symmetrical with respect to the riverbed topography, and that the coefficient decreases sharply on the downstream side of the sandbar because the influence of negative acceleration is large. The above characteristics are verified through numerical simulations as well.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77(2) (2), I_877 - I_882, Japanese


• LABORATORY EXPERIMENTS ON THE ROTATION OF MARIMO AND DEVELOPMENT OF THE MARIMO MODEL

  OGATA Keisuke, NAKAYAMA Keisuke, OYAMA Yoichi, KOMAI Katsuaki, SHINTANI Tetsuya, AMANO Motoshi

  Aegagropila linnaei, Marimo, is a special natural monument of Japan and in danger of extinction. However, the formation mechanism of Marimo has been unresolved. In particular, it is needed to estimate the rotation angle of Marimo, which plays a significant role in the formation of Marimo. Numerical computation is one of the most robust techniques. Thus, we attempted to develop the Marimo model, including the Marimo's movement and its rotation. The Marimo model showed a relatively good reproducibility with the laboratory experiments in terms of rotation when the Marimo was in contact. However, when they were not in contact, the model did not reproduce well. It was also suggested that the rotational moment needs to be taken into account.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77(2) (2), I_1063 - I_1068, Japanese


• INFLUENCING FACTORS ON AIR-SEA CO₂ FLUX AT CIGU LAGOON, TAIWAN

  KAWAHARA Yuki, TSAI Jeng-Wei, LIN Hiroyuki, MATSUMOTO Hiroki, HUNG Meng-chi, HSUEH Mei Li, NAKAYAMA Keisuke

  Cigu Lagoon is a famous lagoon for fish agriculture (oyster) and migration birds, where few seagrasses exist. We aim to investigate the environmental factors affecting carbon fluxes in Cigu Lagoon to understand the influence of fishery. SEM analysis was conducted to understand the influence of environmental factors on the air-sea CO₂ flux. The results suggest that the CO₂ flux is directly influenced by wind speed and indirectly by pH due to the influence of oysters. A three-dimensional environmental model, Fantom, was applied to investigate the effect of the wind on DIC at the water surface. It was demonstrated that strong wind enhances the vertical convection in the water column, resulting in high DIC at the water surface due to the mixing with higher DIC adjacent to the sea bottom.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 77(2) (2), I_841 - I_846, Japanese


• VALIDATION OF SAV MODEL USING LABORATORY EXPERIMENTS

  SASAKI Daisuke, MATSUMOTO Hiroki, NAKAYAMA Keisuke, TADA Kazufumi, LIN Hao-Chi, HAMADA Takuya, SHINTANI Tetsuya

  "Blue carbon", absorbed carbon by photosynthesis in coastal and ocean ecosystem, has been paid attention to as climate change mitigation. The carbon absorption rate varies when seagrass bends due to current, suggesting the necessity of precise estimation of carbon absorption by the blue carbon ecosystem. We developed the Submerged Aquatic Vegetation model (SAV model), which combines SAV motion and its interaction with the current. Therefore, this study aims to verify the SAV model's validity by applying laboratory experiments in an open channel assuming low-density polyethylene as SAV, which agreed with the laboratory experiments.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 77(2) (2), I_205 - I_210, Japanese


• EFFECT OF PHOTOSYNTHETIC ACTIVITY ON THE ABSORPTION AND RELEASE OF DISSOLVED INORGANIC CARBON BY EELGRASS

  Katsuaki KOMAI, Tatsuya SATO, Toshiyuki CHIBA, Keisuke NAKAYAMA

  In present study, the effect of the seasonal difference in photosynthetic activity of eelgrass on the absorption/release characteristics of dissolved inorganic carbon was clarified from the results of model analysis of changes in dissolved inorganic carbon by aquatic tank experiments using eelgrass and chlorophyll-a content analysis. It was revealed that the optimum value of the maximum photosynthetic rate for dissolved inorganic carbon by eelgrass varies depending on the season of the experiment. From the estimated values by the model and the results of the chlorophyll-a content of eelgrass, it was suggested that the difference in the growth stage of eelgrass affected the photosynthetic activity and the maximum photosynthetic rate. The results obtained based on the measured values of the detailed specifications of eelgrass were applied to the model to clarify the relationship between the characteristics of the vertical profile of dissolved inorganic carbon and the branching structure of eelgrass.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 77(2) (2), I_565 - I_570, Japanese


• NUMERICAL SIMULATION OF DISSOLUBED INORGANIC CARBON CONSIDERING EELGRASS RESPIRATION AND PHOTOSYNTHESIS

  Hiroki MATSUMOTO, Keisuke NAKAYAMA, Katsuaki KOMAI, Kazufumi TADA, Hao-Chi LIN, Tetsuya SHINTANI

  This study investigated the effect of eelgrass respiration and photosynthesis on DIC's horizontal distribution at Lake Komuke in northeastern Hokkaido using a newly extended SAV model (Submerged Aquatic vegetation model). The original SAV model successfully predicts the interaction between fluid and vegetation, however it needs enormous computational resources for field scale simulations. Therefore, the Super SAV model, which integrates a few hundred SAVs into only one SAV, was proposed in this study. The Super SAV model was validated by comparing the velocity field and diffusion coefficient with the original SAV model under a current uniform condition. The Super SAV model, which considers respiration and photosynthesis by eelgrass, was incorporated into a three-dimensional hydrodynamic model. The results obtained by the Super SAV model was demonstrated to agree with the observed data in Lake Komuke.

  Japan Society of Civil Engineers, 2021, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 77(2) (2), I_613 - I_618, Japanese


• Breathers in a three-layer fluid

  K. Nakayama, K. G. Lamb

  Nov. 2020, Journal of Fluid Mechanics

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Breaking of Internal Kelvin Waves Shoaling on a Slope

  K. Nakayama, T. Sato, K. Tani, L. Boegman, I. Fujita, T. Shintani

  American Geophysical Union ({AGU}), Oct. 2020, Journal of Geophysical Research: Oceans, 125(10) (10)

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• EVALUATION OF HYDRODYNAMIC EFFECTS ON BLUE CARBON DYNAMICS IN THE YATSUSHIRO SEA

  Bing Xiong, Naoki Saito, Hiroto Komori, Shinichiro Yano, Keisuke Nakayama, Katsuaki Komai, Kei Yajima

  Sep. 2020, Proc. 22nd Int. Conf. on IAHR-APD, 1 - 6

  [Refereed]


• FIELD OBSERVATION ON BLUE CARBON DYNAMICS IN THE YATSUSHIRO SEA CONSIDERING INFLUENCE OF STRATIFICATION

  Naoki Saito, Xion Bing, Hiroto Komori, Shinichiro Yano, Keisuke Nakayama, Katsuaki Komai, Kei Yajima

  Sep. 2020, Proc. 22nd Int. Conf. on IAHR-APD, 1 - 6

  [Refereed]


• APPLICATION OF OPTICAL FLOW TECHNIQUES FOR RIVER SURFACE FLOW MEASUREMENTS

  Jumpei Yagi, Kojiro Tani, Ichiro Fujita, Keisuke Nakayama

  Sep. 2020, Proc. 22nd Int. Conf. on IAHR-APD, 1 - 6

  [Refereed]


• DISCHARGE ESTIMATION BY STIV COMBINED WITH THE MAXIMUM ENTROPY METHOD

  Takuya Hamada, Ichiro Fujita, Kojiro Tani, Keisuke Nakayama

  Sep. 2020, Proc. 22nd Int. Conf. on IAHR-APD, 1 - 6

  [Refereed]


• 琵琶湖における高精度な流動場の解析手法の提案

  王媛, 中山恵介, 岩田遼, 新谷哲也, 速水祐一, 藤原建紀

  Sep. 2020, 土木学会年時講演会講演集, 73


• Integration of Submerged Aquatic Vegetation Motion Within Hydrodynamic Models

  K. Nakayama, T. Shintani, K. Komai, Y. Nakagawa, J. W. Tsai, D. Sasaki, K. Tada, H. Moki, T. Kuwae, K. Watanabe, M. R. Hipsey

  American Geophysical Union ({AGU}), Aug. 2020, Water Resources Research, 56(8) (8)

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Empirical Approach for Modeling of Partition Coefficient on Lead Concentrations in Riverine Sediment

  Saadia Bouragba, Katsuaki Komai, Keisuke Nakayama

  Jul. 2020, International Journal of Environmental Science and Development, 11(7) (7), 352 - 357, English

  [Refereed]

  Scientific journal


• Terrestrial loads of dissolved organic matter drive inter-annual carbon flux in subtropical lakes during times of drought

  Chiu, C.-Y., Jones, J.R., Rusak, J.A., Lin, H.-C., Nakayama, K., Kratz, T.K., Liu, W.-C., Tang, S.-L., Tsai, J.-W.

  Elsevier {BV}, May 2020, Science of the Total Environment, 717, 137052 - 137052

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 浅水状態の粗配置桟粗度上で生じる三角状水面波列に対するソリトン解の適用—APPLICATION OF SOLITON SOLUTION TO TRIANGULE-SHAPE WATER SURFACE WAVE SEQUENCE WITH SPARSELY DISTRIBUTED STRIP ROUGHNESS IN SHALLOW WATER

  2020, 65, Ⅰ_1063 - 1068, Japanese


• 内部ソリトン波の砕波によるエネルギー減衰のモデル化と成層流動場の高精度な再現—ENERGY ATTENUATION MODELLING UNDER THE BREAKING OF INTERNAL SOLITARY WAVES AND REPRODUCTION OF THE STRATIFIED LAKES WITH HIGH ACCURACY

  2020, 65, Ⅰ_1399 - 1404, Japanese


• マリモにおける弾性定数と粘性係数の推定及びMR解析—ESTIMATION OF ELASTICITY AND VISCOSITY OF MARIMOS AND MR DATA ANALYSIS

  2020, 65, Ⅰ_1267 - 1272, Japanese


• DEVELOPMENT OF SUBMERGED AQUATIC VEGETATION MODEL CONSIDERING BRANCH

  SASAKI Daisuke, NAKAYAMA Keisuke, SHINTANI Tetsuya, TADA Kazufumi, MATSUMOTO Hiroki, KOMAI Katsuaki

  When aquatic plants deflect by waves and currents, absorption rate of dissolved inorganic carbon varies dramatically. Therefore, it is necessary to evaluate the effect of wave-current on aquatic plants. In the previous studies, there are significant problems such as not fully considering the interaction between elasticity and currents. In this study, we developed a Submerged Aquatic Vegetation model (SAV model) by including branch and using object-oriented programming that enables to analyze the accurate interaction between wave-current and aquatic plants. As a result, we estimated the values of significant parameters for SAV model from laboratory experiments. Also, Minimum Elastic Modulus of branch (MEM) is revealed to be associated with the length of branch though MEM is not affected by the flow velocity and the position of branch. It was demonstrated that the larger the branch length, the larger the MEM is needed.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 76(2) (2), I_1075 - I_1080, Japanese


• ENERGY ATTENUATION MODELLING UNDER THE BREAKING OF INTERNAL SOLITARY WAVES AND REPRODUCTION OF THE STRATIFIED LAKES WITH HIGH ACCURACY

  WANG Yuan, NAKAYAMA Keisuke, ITO Wataru, IWATA Ryo, SHINTANI Tetsuya, HAYAMI Yuichi, FUJIWARA Tateki

  In recent years, affected by global warming, overturning is suppressed in large lakes such as Lake Biwa and the similar phenomenon is likely to occur in the future. In order to prevent such phenomenon, it is very important to reproduce the stratified lakes with high accuracy. However, the past research based on the hydrostatic pressure approximation did not take the loss of potential energy (����) into consideration, and the analysis of ���� is larger than reality. Therefore, this study is focused on internal solitary waves and tries to model the energy loss under hydrostatic pressure approximation. As a result, the energy loss of internal solitary waves can be modelled under hydrostatic pressure approximation successfully by using frictiontype energy loss and highly accurate analysis of the stratified lakes under hydrostatic conditions becomes possible.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 76(2) (2), I_1399 - I_1404, Japanese


• ENERGY LOSS MODELLING UNDER HYDROSTATIC PRESSURE APPROXIMATION

  IWATA Ryo, NAKAYAMA Keisuke, WANG Yuan, SHINTANI Tetsuya

  Internal solitary waves are likely to be excited by the external forces such as wind in stratified lakes and coastal areas. When the internal solitary waves break on a slope, potential energy (E_p) of the internal solitary wave tends to be lost completely. The previous studies showed that hypoxia recovers on sloping bottom boundaries in Tokyo Bay when a strong wind is given. However, E_p of internal solitary waves cannot be included in a real-scale simulation because of the hydrostatic pressure approximation. Therefore, this study aims to model the energy loss to take account the breaking of internal solitary waves on a slope. As a result, the energy loss of internal solitary waves can be modeled under hydrostatic pressure approximation successfully by using friction-type energy loss not only in laboratory scale phenomena but also in real scale phenomena, Tokyo Bay.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 76(2) (2), I_780 - I_785, Japanese


• ESTIMATION OF ELASTICITY AND VISCOSITY OF MARIMOS AND MR DATA ANALYSIS

  OGATA Keisuke, NAKAYAMA Keisuke, OYAMA Yoichi, KOMAI Katsuaki, HORII Shintaro, SOMIYA Yuichiro, KUMAMOTO Etsuko

  Aegagropila linnaei are natural monuments of Japan and in danger of extinction. However, the formation of Marimos has been unresolved. For the clarification of the creation of Aegagropila linnaei, a numerical computation is one of the most powerful techniques, such as a Distinct Element Method (DEM). We attempted to estimate two significant parameters for DEM, elastic modulus and viscosity coefficients of Aegagropila linnaei by applying laboratory experiments, which revealed that two parameters are constant regardless of size and density. Furthermore, we investigated Marimos by using Magnetic Resonance Imaging, which allows non-destructive investigation of Marimos underwater. The base of Marimos is revealed to move from the outer edge to the centre of Aegagropila linnaei when they grow.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 76(2) (2), I_1267 - I_1272, Japanese


• APPLICATION OF SOLITON SOLUTION TO TRIANGULE-SHAPE WATER SURFACE WAVE SEQUENCE WITH SPARSELY DISTRIBUTED STRIP ROUGHNESS IN SHALLOW WATER

  YAGI Jumpei, HIGASHIKAWA Shinya, TANI Kojiro, FUJITA Ichiro, NAKAYAMA Keisuke

  Triangular-shaped surface waves occur with large amplitude in a river during a flood. The large amplitude surface waves are concerned to cause damage to river structures. Higashikawa et al. (2019) found that the train of triangular-shaped surface waves occurs due to soliton resonance. They assumed that the propagation direction of the soliton resonance inclines to the flow direction when the modified Miles' solution is applied. In this study, we aim to derive theoretical solutions by modifying the hypothesis. As a result, our new solutions agree with the laboratory experiment results better than Higashikawa et al. (2019). Furthermore, we confirmed that triangular-shaped surface waves occur due to soliton resonance.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 76(2) (2), I_1063 - I_1068, Japanese


• FIELD SURVEY ON CO₂ IN SEAWATER FOR REVEALING BLUE CARBON DYNAMICS IN THE YATSUSHIRO SEA

  SAITO Naoki, XIONG Bing, KOMORI Hiroto, YANO Shinichiro, NAKAYAMA Keisuke, KOMAI Katsuaki, YAJIMA Hiroshi

   "Blue carbon", which is carbon fixed by marine organisms, is attracting attention as a new measure to reduce atmospheric CO₂. We carried out field survey regarding the CO₂ partial pressure (pCO₂) in sea water in the Yatsushiro Sea where it is confirmed that habitats of corals and seagrass, in order to reveal the pCO₂ dynamics in actual situation. Moreover, by observation under different mixing conditions, we tried to reveal how stratification can affect on the dynamics. As a result, it was confirmed that with the development of strong stratification, the effect of photosynthesis by phytoplankton was concentrated on the surface and pCO₂ decreased. In addition, it was suggested that the influx of water affected by corals caused the fluctuation of pCO₂. Finally, trial calculation of CO₂ flux between sea and air in daytime shows that the Yatshiro Sea can absorb CO₂ throughout the year, regardless of the mixing conditions.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 76(2) (2), I_901 - I_906, Japanese


• DEVELOPMENT OF A MODEL FOR ESTIMATING OF VERTICAL DISTRIBUTION OF DISSOLVED INORGANIC CARBON DUE TO EELGRASS IN A STRATIFIED FLUID

  Hiroki MATSUMOTO, Keisuke NAKAYAMA, Katsuaki KOMAI, Kazufumi TADA, Daisuke SASAKI, Kenta WATANABE, Atsushi KUBO, Yasuyuki MARUYA

  In order to reveal the carbon uptake mechanism of eelgrass, the vertical distribution of dissolved inorganic carbon (DIC) was estimated by a conceptual model considering the stratification effect at Lake Komuke. The field observation show that the eelgrass meadows change stratification and the vertical distribution of DIC. The conceptual model was verified by comparing with the vertical diffusion coefficients obtained from the Submerged Aquatic Vegetation model (SAV model). As a result, the conceptual model results agreed with the SAV model when eelgrass exists densely in a strong stratified fluid. Additionally, SAV model was improved in order to reduce run-time cost by combining with a hydrostatic model. The improved SAV model shows high accuracy and the run time was reduced dramatically.

  Japan Society of Civil Engineers, 2020, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 76(2) (2), I_869 - I_874, Japanese


• Modeling dissolved inorganic carbon considering submerged aquatic vegetation

  Nakayama, K., Komai, K., Tada, K., Lin, H.C., Yajima, H., Yano, S., Hipsey, M.R., Tsai, J.W.

  Elsevier {BV}, 2020, Ecological Modelling, 431, 109188 - 109188

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Inundation analysis using coupling storage function model with a distributed hydrological model in Kushiro Marsh, Japan

  Sakaguchi, S., Nakayama, K., Kobayashi, K., Komai, K.

  Japan Society of Hydrology and Water Resources (JSHWR) / Japanese Association of Groundwater Hydrology (JAGH) / Japanese Association of Hydrological Sciences (JAHS) / Japanese Society of Physical Hydrology (JSPH), 2020, Hydrological Research Letters, 14(2) (2), 75 - 80, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Non-linear wave equations for free surface flow over a bump

  Sakaguchi, S., Nakayama, K., Vu, T.T.T., Komai, K., Nielsen, P.

  2020, Coastal Engineering Journal, 62(2) (2), 159 - 169, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• CLASSIFICATION OF INTERNAL WAVE BREAKING OVER A SLOPE WITH THE CHANGE IN THE THICKNESS OF PYCNOCLINE

  岩田 遼, 佐藤 啓央, 中山 恵介

  土木学会, Nov. 2019, 水工学論文集 Annual journal of Hydraulic Engineering, JSCE, 64, I_769 - 774, Japanese

  [Refereed]


• RESONANT CHARACTERISTICS OF TRIANGULAR WAVE SEQUENCE OVER SHALLOW FLOW WITH SPARSELY DISTRIBUTED STRIP ROUGHNESS

  東川 真也, 藤田 一郎, 中山 恵介, 谷 昂二郎

  土木学会, Nov. 2019, 水工学論文集 Annual journal of Hydraulic Engineering, JSCE, 64, I_445 - 450, Japanese

  [Refereed]


• ESTIMATION OF ROTATION ANGLE AND CRITICAL VELOCITY OF MARIMOS DUE TO WAVES AND CURRENTS

  Noriko HAYASHI, Keisuke NAKAYAMA, Yoichi OYAMA, Katsuaki KOMAI

  Nov. 2019, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 75(2) (2), I_775 - I_780, Japanese

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• MEASUREMENT OF SEAGRASS DISTRIBUTION BY SATELLITE DATA AND VARIDATION USING DISSOLVED INORGANIC CARBON IN LAGOON

  Katsuaki KOMAI, Hiroshi HAYAKAWA, Tatsuya SATO, Keisuke NAKAYAMA

  Seagrass distribution in a lagoon located near the Sea of Okhotsk was estimated from satellite data, and varidated using DIC and its variation obtained by field observation data. Seagrass distribution was made by converted data from averaged NDVI of satellite Sentinel-2 to seagrass vegetation density. As a result of calculation of DIC model, since field observation data at 17 points in/out of seagrass vegetation area for a period of from July to August in 2018 were successfully represented, seagrass distribution using satellite NDVI was well verified. Bias of calculation results were appeared due to seagrass existence, however, the estimation insufficiency of vegetation under the water and the influence of hydraulic re-sistance of seagrass to tidal current and water quality were likely associated.

  Nov. 2019, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 75(2) (2), I_397 - I_402, Japanese

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• FLOW ANALYSIS IN EELGRASS MEADOW WITH OSCILLATION FLOW FIELD

  TADA Kazufumi, NAKAYAMA Keisuke, NAKANISHI Yutaro, SASAKI Daisuke, KOMAI Katsuaki

  Japan Society of Civil Engineers, Oct. 2019, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 75(2) (2), I_25 - 30, Japanese

  [Refereed]

  Link to Kobe Univ. Repository (Kernel)


• PROCESS UNDERSTANDING OF THE TOGAGAWA RIVER FLOODING 2008 USING A DISTRIBUTED RAINFALL-RUNOFF/FLOOD-INUNDATION MODEL

  KENICHIRO KOBAYASHI, RYO KAWASAKI, ICHIRO FUJITA, KEISUKE NAKAYAMA

  The International Association for Hydro-Environment Engineering and Research (IAHR), Sep. 2019, 38th IAHR World Congress - "Water: Connecting the World"

  International conference proceedings


• Residence time in a lagoon system

  K. Yamamoto, N. Hayashi, K. Nakayama, J.W. Tsai, M.C. Hung, S.C. Hsiao

  Sep. 2019, Proc. 10th Int. Conf. on Asian and Pacific Coasts, 10, English

  [Refereed]

  Scientific journal


• 八代海において有明海との海水交換が成層流動場に与える影響評価

  伊藤航, 中山恵介, 矢野真一郎, 熊柄, 齋藤直輝, 駒井克昭, 矢島啓

   We developed the hydrodynamic model of Yatsushiro Sea in order to analyze stratified flow field and water quality in Yatsushiro Sea. Yatsushiro Sea is connected to Ariake Sea with very narrow strait, which cannot be modelled due to the limitation of computational capacity. Therefore, we made an attempt to develop the SYA (Strait between Yatsushiro Sea and Ariake Sea) model to estimate fluxes of seawater exchange through SYA. It was found that there is no seasonal difference in seawater exchange flux. As a result, field observations were successfully reproduced by applying the SYA model into the Yatsushiro Sea model with good agreements.

  Japan Society of Civil Engineers, Jul. 2019, 土木学会論文集B3（海洋開発）, 75(2) (2), I_977 - I_982, Japanese

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 水深葉長比を考慮した有効水草高さに関する検討

  佐々木大輔, 中山恵介, 中西佑太郎, 中川康之, 田多一史, 駒井克昭

  Jul. 2019, 土木学会論文集B3（海洋開発）, 75(2) (2), I_504 - I_509, Japanese

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Classification of internal solitary wave breaking over a slope

  Nakayama, K., Sato, T., Shimizu, K., Boegman, L.

  2019, Physical Review Fluids, 4(1) (1), 014801, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Oblique reflection of large internal solitary waves in a two-layer fluid

  Nakayama, K., Kakinuma, T., Tsuji, H.

  2019, European Journal of Mechanics, B/Fluids, 74, 81 - 91, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Seasonal changes of the diurnal variation of precipitation in the upper Río Chagres basin, Panamá

  Nakaegawa, T., Pinzon, R., Fabrega, J., Cuevas, J.A., de Lima, H.A., Cordoba, E., Nakayama, K., Lao, J.I.B., Melo, A.L., Gonzalez, D.A., Kusunoki, S.

  2019, PLoS ONE, 14(12) (12), English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Assessment of distributed hydrological model performance for simulation of multi-heavy-metal transport in Harrach River, Algeria

  Bouragba, S., Komai, K., Nakayama, K.

  2019, Water Science and Technology, 80(1) (1), 11 - 24, English

  [Refereed]

  Scientific journal


• 貯水池底層における貧酸素水塊発生機構の解明

  山元幸之助, NAKAYAMA KEISUKE, 藤井智康, 藤原建紀, 清水武俊, KOBAYASHI KENICHIRO

  Dec. 2018, 土木学会論文集B1（水工学）, 74(5) (5), I - 535-I_540, Japanese

  [Refereed]

  Scientific journal


• 浅水流方程式・局所慣性方程式の精度検証と最適空間解像度に関する検討

  KOBAYASHI KENICHIRO, NAKAYAMA KEISUKE, 阪口詩乃

  Dec. 2018, 土木学会論文集B1（水工学）, 74(5) (5), I - 1513-I_1518, Japanese

  [Refereed]

  Scientific journal


• 洪水氾濫シミュレーションにおいて風の影響を考慮する必要性に関する検討

  KOBAYASHI KENICHIRO, NAKAYAMA KEISUKE, 田中翔, 阪口詩乃, 奥勇一郎, 池内幸司

  Dec. 2018, 土木学会論文集B1（水工学）, 74(5) (5), I - 1459-I_1464, Japanese

  [Refereed]

  Scientific journal


• 個別要素法を環境流体解析に組み込んだマリモモデルの開発

  林典子, NAKAYAMA KEISUKE, 尾山洋一, 若菜勇, 山田俊郎, 駒井克昭

  Dec. 2018, 土木学会論文集B1（水工学）, 74(5) (5), I - 517-I_522, Japanese

  [Refereed]

  Scientific journal


• 波・流れ場とアマモ場の相互干渉解析

  中西佑太郎, NAKAYAMA KEISUKE, 中川康之, 茂木博匡, 田多一史, Matthew HIPSEY, 桑江朝比呂

  Nov. 2018, 土木学会論文集B2（海岸工学）, 74(2) (2), I_31 - I_36, Japanese

  [Refereed]

  Scientific journal


• 二層システムにおける内部ソリトン波の斜面上での砕波形態と物質輸送

  佐藤啓央, NAKAYAMA KEISUKE, 清水健司, Leon BOEGMAN

  Nov. 2018, 土木学会論文集B2（海岸工学）, 74(2) (2), I_655 - I_660, Japanese

  [Refereed]

  Scientific journal


• 水深が変化する水域を伝播する内部波の数値解析

  越智直人, 柿沼太郎, NAKAYAMA KEISUKE

  Nov. 2018, 土木学会論文集B2（海岸工学）, 74(2) (2), I_25 - I_30, Japanese

  [Refereed]

  Scientific journal


• 強非線形強分散波動方程式の改良とbumpを有する波動場への適用

  阪口詩乃, NAKAYAMA KEISUKE, Thuy Thi Thu VU, 駒井克昭, Peter NIELSEN

  Nov. 2018, 土木学会論文集B2（海岸工学）, 74(2) (2), I_1 - I_6, Japanese

  [Refereed]

  Scientific journal


• アマモ場における海水中CO2分圧モデルの開発

  田多一史, NAKAYAMA KEISUKE, 桑江朝比呂

  Nov. 2018, 土木学会論文集B2（海岸工学）, 74(2) (2), I_1237 - I_1242, English

  [Refereed]

  Scientific journal


• 成層を考慮したアマモ場における溶存無機炭素の変動解析

  田多一史, NAKAYAMA KEISUKE, 駒井克昭, Jeng-Wei Tsai, 佐藤之信, 桑江朝比呂

  Jul. 2018, 土木学会論文集B3（海洋開発）, 74(2) (2), I_444 - I_449, Japanese

  [Refereed]

  Scientific journal


• 千刈貯水池を対象とした出水時の成層場に関する検討

  NAKAYAMA KEISUKE, 藤原建紀, 藤井智康, 小林健一郎, 中島祐輔

  Mar. 2018, 土木学会論文集B1（水工学）, 74(4) (4), I - 355-I_360, Japanese

  [Refereed]

  Scientific journal


• 解析解を利用した準長波方程式による洪水氾濫解析

  阪口詩乃, NAKAYAMA KEISUKE, 小林健一郎

  Mar. 2018, 土木学会論文集B1（水工学）, 74(4) (4), I - 1423-I_1428, Japanese

  [Refereed]

  Scientific journal


• イオンクロマトグラフィーを利用したBayesian理論による溶存物質の輸送割合推定手法の開発

  駒井克昭, NAKAYAMA KEISUKE, 阪口詩乃

  Mar. 2018, 土木学会論文集B1（水工学）, 74(4) (4), I - 505-I_510, Japanese

  [Refereed]

  Scientific journal


• 河川出水による貯水池の底層水交換モデルの提案

  中山 恵介, 藤原 建紀, 藤井 智康, 小林 健一郎, 清水 武俊, 佐藤 啓央, 山元 幸之助

  2018, 土木学会論文集B1（水工学）, 74(4) (4), I_355 - I_360

  [Refereed]


• A numerical calculation for internal waves over topography

  Taro Kakinuma, Naoto Ochi, Kei Yamashita, Keisuke Nakayama

  American Society of Civil Engineers (ASCE), 2018, Proceedings of the Coastal Engineering Conference, 36(2018) (2018), English

  International conference proceedings


• DEVELOPMENT OF A SEAGRASS MODEL IN WAVES AND UNIDIRECTIONAL CURRENTS

  Yutaro NAKANISHI, Keisuke NAKAYAMA, Yasuyuki NAKAGAWA, Hirotada MOKI, Kazufumi TADA, Mathew HIPSEY, Tomohiro KUWAE

  Japan Society of Civil Engineers, 2018, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 74(2) (2), I_31 - I_36

  Scientific journal


• RUNOFF ANALYSIS USING QUASI-LONGWAVE EQUATIONS

  Shino SAKAGUCHI, Keisuke NAKAYAMA, Kenichiro KOBAYASHI

  Japan Society of Civil Engineers, 2018, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74(4) (4), I_1423 - I_1428

  Scientific journal


• ESTIMATION OF DISSOLVED SUBSTANCES TRANSPORT IN KUSHIRO RIVER BASIN USING DISSOLVED ION PATTERN

  Katsuaki KOMAI, Keisuke NAKAYAMA, Shunsuke HIROKI, Shino SAKAGUCHI

  Large amount of nutrient salt and dissolved organic matter is transported from Kushiro River basin to coastal area. In present paper, seasonality of transport ratio in dissolved inorganic matter from upstream catchment to downstream reach was estimated by using multiple regression mothod incorporating Bayesian theory into major ion pattern in stream water. Transport ratios could be well verified and esti-mated in several percent of errors. Seasonality of contribution ratio was clearly observed in comparison with uncertain errors. Ion representing each catchment should be extracted in advance by using statistical test.

  土木学会, 2018, Annual journal of Hydraulic Engineering, JSCE, 62, I_505 - I_510, Japanese

  [Refereed]

  Scientific journal


• Nitrogen fluxes between the ocean and a river basin using stable isotope analysis

  Nakayama, K., Maruya, Y., Matsumoto, K., Komai, K., Kuwae, T.

  2018, Estuarine, Coastal and Shelf Science, 212, 286 - 293, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• 斜面上における内部ソリトン波の砕波形態の分類

  NAKAYAMA KEISUKE, 佐藤啓央, Leon Boegman, Leon Boegman

   In marginal seas and on continental shelves, interaction of tides and topography excites internal tides, which can degenerate into internal solitary waves (ISWs). Since the breaker type of ISWs is important for sediment resuspension and long-term transport of nutrients, plankton, and hypoxic water, it is needed to categorize the breaker types accurately. Previous studies on ISW breaking over a uniform slope in two-layer stratified fluids demonstrated four breaker types: fission, collapsing, plunging, and surging. The critical depth and density difference between the layers may be important factors, but they have not been considered in the categorization. Using the results of two-dimensional numerical simulations, this study aims to propose new indices for the categorization of ISW breaking, which take the critical depth and the density difference into account. The proposed three indices successfully categorize the four breaker types.

  Japan Society of Civil Engineers, Nov. 2017, 土木学会論文集B2（海岸工学）, 73(2) (2), I_31 - I_36, Japanese

  [Refereed]

  Scientific journal


• 3層系における内部波列による質量輸送速度

  NAKAYAMA KEISUKE, 層系における内部波列による質量輸送速度

   In stratified lakes and oceans, organic matter and nutrients tend to remain within the pycnocline for long time due to suppressed diapycnal mixing by the strong density gradient. Isopycnal mass transport due to Stokes velocity within the pycnocline can be important for long-term processes in the ecology and biogeochemistry. Previous studies have investigated mass transport velocity under sinusoidal internal waves, which exist stably under vertically symmetric stratification. However, studies on mass transport velocity under internal solitary waves, which exist stably under vertically asymmetric stratification, are scarce. This study investigates mass transport velocity due to both sinusoidal and solitary internal waves under three-layer stratification using a fully dispersive, fully nonlinear internal wave model. The model is validated using an analytical solution for mass transport velocity due to sinusoidal waves under vertically symmetric stratification. Mass transport velocity in the middle layer under internal solitary waves tends to be more positive than that under sinusoidal internal waves, and decreases as the top layer thickness increases.

  Japan Society of Civil Engineers, Nov. 2017, 土木学会論文集B2（海岸工学）, 73(2) (2), I_55 - I_60, Japanese

  [Refereed]

  Scientific journal


• 波・流れ場とアマモの連成モデルの構築

  NAKAYAMA KEISUKE, 中西佑太郎, 中川康之, 茂木博匡, 田多一史, 桑江朝比呂

  Japan Society of Civil Engineers, Jun. 2017, 土木学会論文集B3（海洋開発）, 73(2) (2), I_821 - I_826, Japanese

  [Refereed]

  Scientific journal


• Roberts Bank tidal flatにおける干潟内流動と塩分濃度

  NAKAYAMA KEISUKE, 駒井克昭, Robert W. Elner, 桑江朝比呂

   Roberts Bank tidal flat, which is located at the mouth of the Fraser River, has been wellknown as one of the world's largest tidal flats for migratory birds. In the previous studies, biofilm, which exists in a lower salinity region, is found to be significant source of nutrients. However, it has not been revealed how infiltration flow influences salinity inside of a tidal flat. We thus conducted field observations of salinity at the depth of 0.2 m from tidal flat surface. Additionally, in order to clarify horizontal distribution of salinity, two-dimensional salinity model was proposed in this study, which shows very good agreement with field observation results.

  Japan Society of Civil Engineers, Jun. 2017, 土木学会論文集B3（海洋開発）, 73(2) (2), I_618 - I_623, Japanese

  [Refereed]

  Scientific journal


• 貯水池における出水時の成層場鉛直混合に関する検討

  NAKAYAMA KEISUKE, 藤原建紀, 藤井智康, 小林健一郎, 中島祐輔, 佐藤啓央

  土木学会, Mar. 2017, 土木学会論文集B1（水工学）, 73(4) (4), I - 979-I_984, Japanese

  [Refereed]

  Scientific journal


• 洪水氾濫解析を対象とした浅水流方程式の適用性に関する検討

  小林健一郎, NAKAYAMA KEISUKE, 阪口詩乃

  土木学会, Mar. 2017, 土木学会論文集B1（水工学）, 73(4) (4), I_1405 - I_1410, Japanese

  [Refereed]

  Scientific journal


• 蛍光X線分析を利用した細粒土砂の輸送割合と安定同位体比による窒素循環量の推定

  NAKAYAMA KEISUKE, 駒井克昭, 丸谷靖幸, 松本経, 阪口詩乃, 桑江朝比呂

  土木学会, Mar. 2017, 土木学会論文集B1（水工学）, 73(4) (4), I - 1177-I_1182, Japanese

  [Refereed]

  Scientific journal


• Heavy metals transport simulation by physically based distributed modeling approach (case of study: Harrash River, Algeria)

  S. Bouragba, K. Komai, K. Nakayama

  土木学会, Mar. 2017, Annual Journal of Hydraulic Engineering, JSCE, 73(4) (4), I_1159 - I_1164, English

  [Refereed]

  Scientific journal


• INVESTIGATION OF APPLICABILITY OF A LONG WAVE EQUATION FOR INUNDATION ANALYSIS

  Kenichiro KOBAYASHI, Keisuke NAKAYAMA, Shino SAKAGUCHI

  Japan Society of Civil Engineers, 2017, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73(4) (4), I_1405 - I_1410

  Scientific journal


• Development of eel grass model considering interaction with flow fields

  Nakanishi Yutaro, Nakayama Keisuke, Nakagawa Yasuyuki, Tada Kazusi, Mogi Hiromasa, Kuwae Asahiro

  アマモ場内では波・流れの影響を受けて水中の溶存物質が移流拡散しており，アマモと波・流れが相互に影響しあっていることを考慮しつつ，アマモ場内のCO₂ の移流拡散を検討することは，現在に至るまで極めて困難であった．しかし，アマモの移動速度に着目し，抗力・浮力・摩擦・弾性体を考慮したアマモのモデルを作成し，波・流れ場とアマモの動きを連成することによって，アマモの形状およびアマモ場における流速を同時に再現することが出来た．アマモモデルをより高精度にするために，アマモの幅に関して１本のアマモをある高さから４本に分かれると考慮して，幅を急に変化させる場合と滑らかに変化させる場合の2種類の考え，それぞれを検証し結果を考察した．結果は，滑らかに幅を変位させたほうが良好であることが分かった．しかし，その効果は一様流において有意であり，振動流では改善効果は小さいことも分かった．

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017, Proceeding of Annual Conference, 30, 93 - 93, Japanese


• Development of simplified inundation model

  Shino Sakaguchi, Keisuke Nakayama, Kenichiro Kobayashi

  分布型流出モデルを用いて流出解析を行う際，長波方程式を用いる洪水氾濫計算に最も多くの時間を要するため，一般的に現場において再現・予測計算を実施することは困難である．汎用的なPCを利用して現場において解析を容易に実施できるようにするためには，洪水氾濫計算を高速化し，計算負荷を小さくする必要がある．
  そこで本研究では，長波方程式に代わるモデルとして，段波モデル，修正段波モデル，キネマティックウェーブ理論に基づくモデルの３つの簡易洪水氾濫モデルを提案し，それぞれのモデルの再現性の検証を行った．再現性の検証は長波方程式を解いた結果を厳密解として行った．再現性の評価はCoDを用いたフロントの形状，およびフロント位置の比較により行う．
  検証の結果，修正段波モデルを用いた場合が最も再現性が良いことが分かった．また，修正段波モデルを用いて計算を実行するとフロント形状が滑らかになる特徴があり，数値計算上の不安定が生じにくいこともわかった．その理由として，段波の進行に対して逆方向の流速を考慮しているためであると考えることができ，この点でも修正段波モデルは優れたモデルであると言える．
  計算速度は簡易洪水氾濫モデルを用いた計算の場合，厳密解を求める計算と比較して約12倍になった．つまり，実際の洪水氾濫に適用する際にも大きな時間短縮を見込むことができる．
  今後は，今回良い結果が得られたモデルについて粗度の効果及び勾配の効果を考慮できるよう改良し，実際の洪水氾濫計算に適用することを試みる．

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017, Proceeding of Annual Conference, 30, 74 - 74, Japanese


• Mass transport by internal solitary wave breaking on a uniform slope

  Sato Takahiro, Nakayama Keisuke, Shimizu Kenji, Boegman Leon

  沿岸域において，風や潮汐などの外力が与えられると密度界面に内部波が発生し，内部波は内部ソリトン波として安定して進行し，やがて沿岸域の斜面上などで砕波する．その際fission，plunging，collapsing，surgingの4種類の砕波形態が発生することが確認されており，その発生条件は2層システムを考えた場合の密度差，沿岸域の斜面勾配，内部ソリトン波の波高などによって決まる．さらに，過去の研究において，砕波形態が異なることで輸送フラックス等が大きく変化するため，物質輸送のされ方が異なることが示されている．そこで本研究では，物質が貯留されやすいのは密度界面であることを考慮し，砕波形態が異なるときの密度界面における物質輸送の違いを確かめた．主たる結果として，fission，plungingはcollapsing，surgingと比べて沿岸域への輸送エネルギーが大きいことが分かった．また，fission型の砕波発生時には，下層にある貧酸素水塊などの有害な物質がトラップされたコアによって沿岸域の浅い位置まで輸送されることが分かった．

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017, Proceeding of Annual Conference, 30, 94 - 94, Japanese


• Effects of topography and Earth's rotation on the oblique interaction of internal solitary-like waves in the Andaman Sea

  Shimizu, K., Nakayama, K.

  2017, Journal of Geophysical Research: Oceans, 122(9) (9), 7449 - 7465, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• DIURNAL VARIATIONS OF CO₂ FUGACITY IN AN URBANIZED SHALLOW WATER

  TADA Kazufumi, TOKORO Tatsuki, WATANABE Kenta, NAKAYAMA Keisuke, KUWAE Tomohiro

   To investigate the diurnal changes of water CO₂ fugacity in urbanized shallow waters, we performed in situ measurements throughout the day in both summer and winter in Hiragata Bay located in Yokohama. We statistically analyzed the observed data set using the structured equation modeling (SEM) and the path analysis. As a result, we found that the diurnal variation in the fugacity of CO₂ was largely affected by the TA and DIC changes that are moderated mainly by urban drainage and biological metabolism.

  Japan Society of Civil Engineers, 2017, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 73(2) (2), I_1297 - I_1302, Japanese

  [Refereed]

  Scientific journal


• 表面波・内部波共存場における孤立波解

  山下啓, 柿沼太郎, NAKAYAMA KEISUKE

   The numerical solutions, for the coexisting fields of surface and internal solitary waves, were obtained using the nonlinear wave equations, based on the variational principle. In the coexisting fields of the surface and internal solitary waves, the phase velocity of the surface-mode solitary wave, was smaller than that of the surface solitary wave for the corresponding one-layer fluid; conversely, the phase velocity of the internal-mode solitary wave, was smaller than that of the corresponding internal solitary wave without a surface wave. The maximum wave height of the internal-mode internal solitary wave, was larger than that of the corresponding internal solitary wave without a surface wave. The wave height ratio between the internal-mode surface and internal solitary waves, was smaller than the linear shallow water solution; their difference increased as the relative wave height of the internal-mode internal solitary wave increased.

  Japan Society of Civil Engineers, Nov. 2016, 土木学会論文集B2（海岸工学）, 72(2) (2), I_13 - I_18, Japanese

  [Refereed]

  Scientific journal


• 渦度を考慮した強非線形強分散波動方程式による解析

  NAKAYAMA KEISUKE, 柿沼太郎

   In many studies regarding surface wave field using vertically integrated wave equations, vorticity effect is often neglected. However, in the previous studies, it has been revealed that bulbous waves occur, which have more round shape, when surface waves progress over a mild slope on shear flows. On the other hand, trochoidal wave is considered one of the most typical surface waves with vorticity. Some previous studies proposed fully-nonliear and strongly-dispersive wave equations with vorticity, but it has not been confirmed whether the equations can be applied to analyze trochoidal waves qualitatively. Therefore, this study aims to investigate the applicability of the fully-nonliear and strongly-dispersive wave equations with vorticity by using the trochoidal wave theory. Also, bulbous waves are found to be reproduced by using the proposed equation.

  Japan Society of Civil Engineers, Nov. 2016, 土木学会論文集B2（海岸工学）, 72(2) (2), I_1 - I_6, Japanese

  [Refereed]

  Scientific journal


• ソリトン波群の共鳴を対象とした強非線形強分散波動方程式による解析

  NAKAYAMA KEISUKE, 清水健司, 柿沼太郎, 辻英一

   It has been known that the resonance of an incident solitary wave and the reflected wave from a oblique boundary increases the wave amplitude by a factor of up to 3.7, which is close to the theoretically derived value, 4.0, by Miles. Although solitary wave train is induced by the deformation of Tsunami surge reaches a river bend, previous studies investigated the resonance of only two solitary waves. In this study, we investigate the interactions of four solitary waves as a first step towards understanding the resonance of solitary wave trains. As a result, the maximum amplification factor is revealed to reach up to 3.8. Also, we find that the interaction of reflected and incident solitary waves is not (3142)-type but always O-type, which demonstrates that it may be possible to analyze the interaction of solitary wave train easily by using the theory proposed in the study.

  Japan Society of Civil Engineers, Nov. 2016, 土木学会論文集B2（海岸工学）, 72(2) (2), I_7 - I_12, Japanese

  [Refereed]

  Scientific journal


• 表面孤立波及び内部孤立波の特性

  山下啓, 柿沼太郎, NAKAYAMA KEISUKE

   The nonlinear steady wave equations based on the variational principle, were solved using the Newton-Raphson method, to find the numerical solutions for both surface and internal solitary waves. The ratio of kinetic energy to total energy for surface solitary waves increased, as the ratio of wave height to the still water depth increased. Conversely, the ratio of kinetic energy to total energy for internal solitary waves increased, when the ratio of wave height to the maximum wave height is average. The solitary waves propagation also was numerically simulated, by applying the time-dependent model, with the initial conditions obtained using the present method for the large-amplitude surface and internal solitary waves.

  Japan Society of Civil Engineers, Jul. 2016, 土木学会論文集, 72(1) (1), 27 - 41, Japanese

  [Refereed]

  Scientific journal


• 阿寒湖チュウルイ湾におけるマリモに回転運動を与える風波の将来予測に向けて

  佐野史弥, NAKAYAMA KEISUKE, 山田俊郎, 佐藤之信, 丸谷靖幸, 駒井克昭, 尾山洋一, 若菜勇

   Marimo is revealed to be formed by the rotation of Marimo itself due to the wind waves, which enhances photosynthesis over the entire Marimo-surface. Marimo was registered as a special natural treasure in 1952 because Marimo exists in Lake Akan only all over the world. Recently, it is found that meteorological conditions have been changing due to climate change, which may also change wind speed and wind direction. Therefore, the decrease in wind speed would reduce the occurrence of wind waves. This study thus aims to project wind speed by using GCMs. As a result, the projection demonstrated that wind speed increases in the future, which may enhance the rotation of Marimo.

  Japan Society of Civil Engineers, Jun. 2016, 土木学会論文集B3（海洋開発）, 72(2) (2), I_1021 - I_1026, Japanese

  [Refereed]

  Scientific journal


• Roberts Bank tidal flatにおけるbiofilm形成に重要な物理・塩分環境の要因解析

  NAKAYAMA KEISUKE, 駒井克昭, Robert W. Elner, 桑江朝比呂

   There eixt huge tidal flats in Roberts Bank, Vancouver, which is one of the world's largest tidal flats for migratory birds. Since Roberts Bank tidal flat is located at the mouth of the large river, Fraser River, it is expected that ecological and hydrological enviromnents are affected by snow melt flood. Although biofilm is revealed to be one of the most significant factor for migratory birds, it has not been found how biofilm is formed and is sustained. This study thus aims to investigate salinity, which is expected to be significant factor for the formation of biofilm. As results, hydraulic pressure is found to be always negative from inland to the ocean, which forms stable advection and diffusion conditions inside of the tidal flat, and it is found that positive salinity gradient is also formed inside of the tidal flat stably from inland to the ocean.

  Japan Society of Civil Engineers, Jun. 2016, 土木学会論文集B3（海洋開発）, 72(2) (2), I_1099 - I_1104, Japanese

  [Refereed]

  Scientific journal


• Suspended sediment transport estimation by X-ray fluorescence analysis

  C. Beitia, NAKAYAMA KEISUKE, Y. Maruya, N. Ohtsu, S. Yamasaki, M. Yamane, A. Wyatt, K. Komai

  Mar. 2016, Annual Journal of Hydraulic Engineering, JSCE, 72(4) (4), I_1039 - I_1044, English

  [Refereed]

  Scientific journal


• DISTRIBUTION AND VARIATION OF DISSOLVED ORGANIC MATTER AND NUTRIENT IN SNOWMELT SEASON IN TIDALFLAT IN LAKE KOMUKE

  TAKEUCHI Tomohiko, KOMAI Katsuaki, NAKAYAMA Keisuke, WATANABE Kenta, ICHIMI Kazuhiko, YAMADA Toshiro, KUWAE Tomohiro

   Dissolved organic matter was measured by using Fluorescence Spectroscopy (FS) along with salinity from snowmelt season to summer at a tidal flat in Lake Komuke at the northeast of Hokkaido. Seasonalities of dissolved nitrogen and phosphorus concentrations were also examined to clarify the dynamics of nitrogen and phosphorus in sediment-water interfaces. Salinity decreases during the snowmelt season, and FS revealed that fulvic acid-like and humic acid-like fluorescence intensities were higher in sediment pore water than in surface water especially in tidepool due to accumulation of organic matter production. It is likely that NH_4-N and PO_4-P concentrations in surface sediment were mainly affected by redox condition change triggered by tidal action and infiltration flow in shore side.

  Japan Society of Civil Engineers, 2016, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 72(4) (4), I_661 - I_666, Japanese

  [Refereed]

  Scientific journal


• PREDICTION OF SPATIAL AND TEMPORAL VARIATION OF AIR-SEA CO₂ FLUX DURING SPRING FLOOD IN LAKE KOMUKE

  TADA Kazufumi, NAKAYAMA Keisuke, TOKORO Tatsuki, WATANABE Kenta, KUWAE Tomohiro

   In Lake Komuke, which is an important lagoon as carbon sinks, we analyzed previous data and found that salinity and biological metabolism (e.g., photosynthesis and respiration as shown by ΔDIC) are the two key environmental factors affecting CO₂ fugacity in the water column. Further, the data were analyzed using an approximate expression and the numerical computations using three-dimensional numerical model during spring flood to predict spatial and temporal variation of air-sea CO₂ flux. Results show that air-sea CO₂ flux changes into negative (i.e., absorption) when the lake is autotrophic with ΔDIC being < -100μmol/kg.

  Japan Society of Civil Engineers, 2016, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 72(2) (2), I_982 - I_987, Japanese

  [Refereed]

  Scientific journal


• Reversal of Secondary Flows in a Sharp Channel Bend

  Nakayama, K., Nguyen, D.H., Shintani, T., Komai, K.

  2016, Coastal Engineering Journal, 58(2) (2), 1650002, English

  [Refereed]

  Scientific journal


• CHARACTERISTICS OF WATER QUALITY FOCUSED ON SNOWMELT-RELATED GROUNDWATER DISCHARGE INTO LAKE KOMUKE

  TADA Kazufumi, NAKAYAMA Keisuke, TOKORO Tatsuki, WATANABE Kenta, KUWAE Tomohiro

   The awareness of coastal blue carbon is increasing, and the dynamics of the CO₂ fugacity (fCO₂) in shallow coastal waters are becoming critical for evaluation of CO₂ fluxes. We carried out numerical computations using a three-dimensional environmental flow model including snowmelt-related groundwater discharge and estimated fCO₂ in water from salinity, biological metabolism, and calcification. Under the influence of the low salinity from the growndwater, fCO₂ in water was found to increase slightly as a result of the opposite effect of a decrease in fCO₂ with decreasing DIC and an increase in fCO₂ with decreasing TA.

  Japan Society of Civil Engineers, 2016, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 72(2) (2), I_1363 - I_1368, Japanese

  [Refereed]

  Scientific journal


• 超大型浮体構造物が有する津波高さ低減効果の数値解析

  中平達也, 柿沼太郎, 勘場隆嗣, 村上桂広, NAKAYAMA KEISUKE, 栁雄大, 山下啓

  A numerical simulation of the nonlinear interaction between a floating thin-plate and surface waves has been generated to study the decrease of tsunami height in propagation of tsunamis through a very large floating structure (VLFS). The reduction coefficient of tsunami height becomes larger as the length as well as the flexural rigidity of VLFS is larger. The tsunami height also shows a larger reduction coefficient in case the wave height of incident tsunami is larger. In two-dimensional propagation of tsunamis, two waves travel away from the sides of VLFS, leading to the additional reduction of tsunami height.

  Japan Society of Civil Engineers, Nov. 2015, 土木学会論文集B2（海岸工学）, 71(2) (2), I_1033 - I_1038, Japanese

  [Refereed]

  Scientific journal


• 河川津波を対象とした強非線形強分散波動方程式によるソリトン波の解析

  NAKAYAMA KEISUKE

  Nov. 2015, 土木学会論文集B2（海岸工学）, 71(2) (2), I_1 - I_6, Japanese

  [Refereed]

  Scientific journal


• マリモ球状体に回転運動を引き起こす阿寒湖チュウルイ湾の風波特性

  NAKAYAMA KEISUKE, 伊藤権吾, 若菜勇, 北村武文, 佐藤之信, 駒井克昭, 竹内友彦

  Jun. 2015, 土木学会論文集B3（海洋開発）, 71(2) (2), I_913 - I_918, Japanese

  [Refereed]

  Scientific journal


• オホーツク海における流氷移動ベクトル推定手法に関する検討

  佐野史弥, NAKAYAMA KEISUKE, 舘山一孝, 佐藤之信, 駒井克昭

  Jun. 2015, 土木学会論文集B3（海洋開発）, 71(2) (2), I_217 - I_222, Japanese

  [Refereed]

  Scientific journal


• オホーツク海における流氷と波浪・風速の関係について

  佐藤之信, NAKAYAMA KEISUKE, 舘山一孝, 佐野史弥, 駒井克昭

  Jun. 2015, 土木学会論文集B3（海洋開発）, 71(2) (2), I_211 - I_216, Japanese

  [Refereed]

  Scientific journal


• 生物の細胞組織構造を模した流体シミュレーターの設計と検証

  新谷哲也, NAKAYAMA KEISUKE

  We have designed a hydrodynamic simulator with an idea inspired from biological-cell structure. The simulator updates status of cell and membrane objects by nerve-like objects, rather than updates values stored in index-based numeric matrices. The water body may be composed of a single cell (unicellular), or cells (multicellular) interconnected through membranes. The membrane acts as a flux-controller between cells on both sides, i.e., computes advection and diffusion fluxes. Dependent variables and source terms are all objects and embedded in a cell like organelles of a biological cell. Each model object is implemented in C++ to obtain reasonable computational speed, and used from a script language Python to increase user flexibility and extensibility. We explained the advantages of the present design against to the previous ones, and confirmed the accuracy of the present model using analytical solutions.

  Japan Society of Civil Engineers, Mar. 2015, 土木学会論文集B1（水工学）, 71(4) (4), I_283 - I_288, Japanese

  [Refereed]

  Scientific journal


• 強非線形強分散3層モデルを用いた成層湖応答解析

  NAKAYAMA KEISUKE, 吉江祐人, 新谷哲也, 柿沼太郎, H. D. Nguyen, 佐藤之信, 駒井克昭

  This study describes the development of a three-layer model based on a fully-nonlinear and strongly-dispersive internal wave model and its application to a stratified lake response. The efficient numerical model for three-layer system is needed to analyze non-linear and non-hydrostatic lake response as a two-layer model often fails to illustrate realistic stratified lake responses. Therefore, this study aims to develop a three-layer model based on the fully-nonlinear and strongly-dispersive internal wave model (the three-layer FSI model). The three-layer FSI model was verified by simulating the belt-driven three-layer laboratory experiments by Stevens & Imberger (1996). The present model well predicts the measured results of the experiments and supports the classification by the Wedderburn number and Csanady's theory. The computed results also show the importance of non-hydrostatic pressure on the generation of the internal solitary wave during upwelling process.

  Japan Society of Civil Engineers, Mar. 2015, 土木学会論文集B1（水工学）, 71(4) (4), I_793 - I_798, Japanese

  [Refereed]

  Scientific journal


• New analytical form of salt intrusion model in funnel shaped estuaries: application to the Abashiri River

  H. D. Nguyen, NAKAYAMA KEISUKE, T. Shintani, K. Komai

  土木学会, Mar. 2015, Journal of JSCE, 71(4) (4), I_19 - I_24, English

  [Refereed]

  Scientific journal


• NEW ANALYTICAL FORM OF SALT INTRUSION MODEL IN FUNNEL SHAPED ESTUARIES: APPLICATION TO THE ABASHIRI RIVER

  NGUYEN Hoang-Duc, NAKAYAMA Keisuke, SHINTANI Tetsuya, KOMAI Katsuaki

  Prediction of salinity is of significant importance to the water management in estuaries. Although nowadays advanced numerical three-dimensional models are available that can provide detailed information on the salinity and mixing processes, there is still a need for simple tools to be performed in order to investigate the resultant effects of physical quantities on the salinity distribution. The analytical analysis presented in this paper may serve these needs. A new analytical form of the salt intrusion model was developed for use in funnel shaped estuaries, where little known about the effects of the channel shape and hydraulic parameters on the salinity distribution. The newly developed analytical model was well-tested against observational salinity data in the Abashiri River estuary under different tidal conditions and river discharge rates.

  Japan Society of Civil Engineers, 2015, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71(4) (4), I_19 - I_24, Japanese


• DEVELOPMENT OF OBJECT-ORIENTED GEOPHYSICAL FLOW CIRCULATION MODEL, GeoCIRC, WITH FOCUS ON INFILTRATION PROCESS

  NAKAYAMA Keisuke, SHINTANI Tetsuya

  We propose a new geophysical flow circulation model (GeoCIRC) based on object-oriented programming to compute surface and ground water flows. In this study, we focus on an infiltration processes and illustrate the basic structure of the model. The computational domain is discretized with vertical column objects that compute vertical infiltration processes within each column. They are horizontally interconnected and compute horizontal infiltration processes. The each column object consists of layer objects of different properties and resolutions to express weather, ground and geological characteristics. As a computational example, vertical circulation due to the horizontal density difference was reproduced. Then, to verify the accuracy of the model, GeoCIRC was applied to river discharge process in the Kushiro River. The computed results showed good agreements with the CoD of 0.95 and 0.81 for the Gojukkoku and Hirosato river discharge stations, respectively.

  Japan Society of Civil Engineers, 2015, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71(4) (4), I_283 - I_288, Japanese


• ANALYSIS OF SOLITON RESONANCE BY USING FULLY-NONLINEAR AND STRONGLY-DISPERSIVE WAVE MODEL

  NAKAYAMA Keisuke

  Many investigations related to soliton resonance with the large initial amplitude of surface waves have been done in the previous studies by using numerical computaions and laboratory experiments. However, less attention has been paid to small intitial amplitude waves in the analysis of soliton resonance. Therefore, this study aims to investigate soliton resonance with the initial amplitude of 10 % of the total water-depth for surface waves by using the fully-nonlinear and strongly-dispersive wave model. As a result, the amplification rate was found to reach to 3.6 times as large as the initial amplitude. Also, the large amplification rate was found to appear when the initial shape of a solitary wave can be modeled by the KdV theory.

  Japan Society of Civil Engineers, 2015, PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING, 71(2) (2), I_1 - I_6, Japanese


• Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis

  Nakayama, K., Maruya, Y., Matsumoto, K., Komata, M., Komai, K., Kuwae, T.

  Copernicus GmbH, 2015, Biogeosciences Discussions, 12(21) (21), 18185 - 18211, English

  [Refereed]

  Scientific journal


• INFLUENCE OF INFILTRATION FLOW ACCOMPANIED BY SNOWMELT ON WATER QUALITY IN TIDALFLATS IN LAKE KOMUKE

  TAKEUCHI Tomohiko, KOMAI Katsuaki, NAKAYAMA Keisuke, WATANABE Kenta, ICHIMI Kazuhiko, SATO Yukinobu, KUWAE Tomohiro

   In Lake Komuke, located in the northeast of Hokkaido, salinity and water level, and groundwater level of the vicinity of tidal flats were observed in the tidal flat in the snowmelt season to summer, and numerical analysis of the infiltration flow accompanied by snowmelt. In field observation results, water level in terrestrial groundwater level and tidal flats, landward groundwater level was higher in the snowmelt season than the other season. From further results of numerical analysis, the salinity in tidal flat was forced not to increase widely in the case of high landward groundwater level than in the case of low landward groundwater level. Moreover, up-welling was slightly strong in the case of high groundwater level, and made sediment salinity lower. The aquatic organisms can live in low salinity zone kept in the tidal flat in the spring season. It is the evidence that the many birds feeding these aquatic organisms in the spring season are frequently observed.

  Japan Society of Civil Engineers, 2015, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 71(2) (2), I_856 - I_861, Japanese

  [Refereed]

  Scientific journal


• A Study on Restoration of Eelgrass (Zostera marina) Damaged by Tsunami in Miyako Bay

  T. Okada, Y. Maruya, K. Nakayama, E. Iseri

  The eelgrass in Miyako Bay was greatly damaged by the tsunami. For future restoration of the eelgrass, we collected sediments from 110 stations in the bay and analyzed particle-size distribution and chemical composition in 2012 and 2013. The distribution of eelgrass was also measured at the same stations. The sediments on the south and west coast were suitable for eelgrass. On the other hand, the sediments on the east coast were coarser. The chemical composition indicated that we could not expect the supply of sand from the main river to the east coast. We estimated that the restoration of eelgrass on the east coast would be slower than on the west and south coast.

  Japan Society of Civil Engineers, Nov. 2014, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 70(2) (2), 1186 - 1190, Japanese

  [Refereed]

  Scientific journal


• 宮古湾における津波被害からのアマモ場の復元の可能性について

  岡田知也, 丸谷靖幸, NAKAYAMA KEISUKE

  Nov. 2014, 土木学会論文集B2（海岸工学）, 70(2) (2), I_1186 - I_1190, Japanese

  [Refereed]

  Scientific journal


• 渦度を考慮した強非線形強分散波動方程式により再現されたソリトン波の解析

  吉江祐人, NAKAYAMA KEISUKE

  To analyze the influence of vorticity on surface and internal waves, Kakinuma and Nakayama (2007) proposed a fully-nonlinear strongly-dispersive internal wave equation by taking into acount vorticity effects (FSI model). In this study, we made an attempt to apply the FSI model to reproduce the trochoidal waves in order to investigate the reliability of the FSI model in flow fields with vorticity. As a result, we obatained good agreement between the FSI model and the theoretical solutions. Furthermore, we applied the FSI model into solitary waves with positive vorticity, which results in the supression of wave celerity and wave height.

  Japan Society of Civil Engineers, Nov. 2014, 土木学会論文集B2（海岸工学）, 70(2) (2), I_1 - I_5, Japanese

  [Refereed]

  Scientific journal


• Identification of the dominant suspended sediment sources in a river basin by using X-ray fluorescence analysis as a fingerprint-type method

  C. Beitia, NAKAYAMA KEISUKE, N. Ohtsu, M. Yamane, S. Yamasaki, Y. Maruya, K. Komai

  Sep. 2014, Proceedings of 19th Congress of the Asia and Pacific Division of the International Association for Hydro-Environment Engineering and Research, 19, English

  [Refereed]

  International conference proceedings


• Characteristics of river water and nutrient discharge in a wetland

  K. Komai, NAKAYAMA KEISUKE, Y. Fukuoka, M. Kawai, S. Nakashita, Y. Ichikawa

  Sep. 2014, Proceedings of 19th Congress of the Asia and Pacific Division of the International Association for Hydro-Environment Engineering and Research, 19, English

  [Refereed]

  International conference proceedings


• Nonlinear oblique interaction of large amplitude internal solitary waves

  NAKAYAMA KEISUKE, Y. Sato, Y. Yoshie, T. Kakinuma, H. D. Nguyen, K. Komai

  Jul. 2014, Proceedings of International Conference of Coastal Engineering, 34, English

  [Refereed]

  International conference proceedings


• 異なる斜面勾配における内部ケルビン波の砕波により誘起される流れ

  小窪一毅, NAKAYAMA KEISUKE, 新谷哲也, 大塚淳一, 渡部靖憲, 柿沼太郎, 駒井克昭, 清水健司

  Jun. 2014, 土木学会論文集B3（海洋開発）, 70(2) (2), I_201 - I_206, Japanese

  [Refereed]

  Scientific journal


• 内部ケルビン波の砕波による水平循環の発達と減衰

  小窪一毅, NAKAYAMA KEISUKE, 新谷哲也, 大塚淳一, 渡部靖憲, 柿沼太郎, 駒井克昭, 清水健司

  This study describes a horizontal circulation induced by the breaking of internal Kelvin waves over a uniform slope. In lakes or coastal regions, wind stress over a water surface or tide at the bay mouth may induce internal waves, which deform as internal Kelvin waves when the inertia radius is equal or less than the spatial scale of a lake or a bay. In general, internal Kelvin waves break due to the topographical features, such as a slope, which is revealed to cause horizontal circulation in the upper layer. The previous studies demonstrated that a horizontal circulation is induced due to the secondary lateral current due to the breaking of internal Kelvin waves over a slope. However, the development and damping of the horizontal circulation have not been clarified. Therefore, this study aims to investigate the occurrence of a horizontal circulation due to the internal Kelvin wave breaking over a slope by using laboratory experiments and numerical computations.

  Japan Society of Civil Engineers, Mar. 2014, 土木学会論文集B1（水工学）, 70(4) (4), I_1195 - I_1200, Japanese

  [Refereed]

  Scientific journal


• 知床を対象としたMRI-AGCM3.1Sを用いた栄養流出量の将来予測に向けて

  丸谷靖幸, NAKAYAMA KEISUKE, 仲江川敏之, 井上徹教, 小俣雅嗣, 石田哲也, 駒井克昭

  The Shiretoko Peninsula which is located in the eastern part of Hokkaido, where nutrient circulataion between inland and the ocean is revealed to play a great role in ecological system. Because of the unique system, "Shiretoko" was registered as the World Natural Heritage. However, previous studies demonstrated that precipitation pattern has been affected by climate change, which may cause the change in the ecological system. Therefore, this study aims to evaluate nutrient flux from the inland to the ocean in the future. According to the previous studies, precipitation is consdered one of the most significant components controlling nutrient supply. Two bias correction techniques were applied by using the MRI-AGCM3.1S. As a result, it is revealed that the cdf correction techique shows better reproduction regarding the nutrient flux compared to the normal distribution correction technique.

  Japan Society of Civil Engineers, Mar. 2014, 土木学会論文集B1（水工学）, 70(4) (4), I_1219 - I_1224, Japanese

  [Refereed]

  Scientific journal


• 汽水湖における有機泥の沈降速度の推定と界面特性に関する考察

  駒井克昭, 日比野忠史, 中下慎也, 戸塚優平, 伊藤立誠, 丸谷靖幸, NAKAYAMA KEISUKE

  Distribution of settling velocity and characteristics of particle-water interface were discussed by using organic mud in Lake Abashiri located in a cold region, east Hokkaido in Japan. The distributions of settling velocity were estimated from temporal variations measured by laser diffraction analyzer. Since the settling velocity of cray mineral sample having low cohesiveness with dispersing agent agreed well with theoritical value, the analytical method were well verified. Comparing with the model consdering organic substances in floc, floc structure varies with floc size in lake water less than in distilled water. Zeta potential representing interface characteristics of organic mud is closely related to dissolved divalent-ion derived from sea water and humic-like organic substance.

  Japan Society of Civil Engineers, Mar. 2014, 土木学会論文集B1（水工学）, 70(4) (4), I_1585 - I_1590, Japanese

  [Refereed]

  Scientific journal


• Horizontal and residual circulations driven by wind stress curl in Tokyo Bay

  Nakayama, K., Shintani, T., Shimizu, K., Okada, T., Hinata, H., Komai, K.

  Blackwell Publishing Ltd, 2014, Journal of Geophysical Research: Oceans, 119(3) (3), 1977 - 1992, English

  [Refereed]

  Scientific journal


• INVESTIGATION OF WATER QUALITY AND FLOW CHARACTERISTIC IN LAKE KOMUKE

  YOSHIE Yuto, MARUYA Yasuyuki, NAKAYAMA Keisuke, KOMAI Katsuaki, SHINTANI Tetsuya, WATANABE Kenta, ICHIMI Kazuhiko, KUWAE Tomohiro

   In Lake Komuke, which is one of the most significant lakes for immigration birds, we carried out field experiments of flow field and water quality. Lake Komuke consists of a main lake and the other two small lakes. The main lake is found to have higher salinity compared to the other two small lakes. During the snow melt period, the small lakes are found to have less salinity compared to summer, which is confirmed by the numerical computations using three-dimensional numerical model. As a result, tidal flats in the small lakes have larger residual time of sea water which is significant for immigration birds.

  Japan Society of Civil Engineers, 2014, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 70(2) (2), I_1176 - I_1181, Japanese

  [Refereed]

  Scientific journal


• SEASONAL VARIATION AND DISTRIBUTION OF WATER QUALITY IN TIDAL FLATS IN LAKE KOMUKE

  KOMAI Katsuaki, NAKAYAMA Keisuke, MATSUBARA Kenya, KAWAGUCHI Takayuki, YAMASAKI Shintaro, WATANABE Kenta, ICHIMI Kazuhiko, KUWAE Tomohiro

   In Lake Komuke, an important flyway in Japan, salinity, water level, and seepage flow were observed in tidal flats and seasonal variation of dissolved organic matters were identified by fluorescence spectroscopy in order to clarify the relationship between water qualities and groundwater flow during spring and summer. At the offshore of the sandbar, the seasonality of fluorescence intensity of fulvic acid-like substances derived from soil in large lake means the seasonal variation of influence of river water and groundwater on water quality in the tidal flat. Groundwater in the tidal flat flew upward by an order of magnitude larger in spring than in summer. From the results of surface water in the tidal flat and the profiles of groundwater, upward flow likely reduces the increase of salinity in the groundwater.

  Japan Society of Civil Engineers, 2014, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 70(2) (2), I_1182 - I_1187, Japanese

  [Refereed]

  Scientific journal


• Adaptive management in Kushiro Wetland in the context of salt wedge intrusion due to sea level rise

  A. Nakamoto, NAKAYAMA KEISUKE, T. Shintani, Y. Maruya, K. Komai, T. Ishida, Y. Makiguchi

  Climate change has been revealed to increase the occurrence of natural disasters and to damage ecological systems. In coastal regions, there are many environmentally significant areas from the viewpoint of biodiversity, such as areas registered under the Ramsar Convention. The Kushiro Wetland is the largest wetland and one of the most significant natural systems in Japan, remaining mostly unaffected by human activity. In the wetland, there are many species, which do not tolerate saltwater. When the sea level rises, the communities of freshwater plants and fish may die out due to the extension of salt wedge intrusion along the Kushiro River. Therefore, in this study we make an attempt to understand the impact of sea level rise on the ecological system of the wetland by using a three-dimensional numerical model, which allows us to evaluate the effect of sea level rise on salt wedge intrusion. It is revealed that the National Park area may be affected by salt water when sea level rise reaches about 0.15 m. Also, the maximum sea level rise may induce saltwater intrusion into the Ramsar area. As a result, we proposed an adaptive management strategy for protecting the ecological system of the wetland from salt wedge intrusion.
  

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Dec. 2013, Hydrological Research Letters, 7(1) (1), 1 - 5, English

  [Refereed]

  Scientific journal


• 内部ケルビン波の砕波による水平循環の発生機構解明

  小窪一毅, NAKAYAMA KEISUKE, 新谷哲也, 柿沼太郎, 大塚淳一, 渡部靖憲, 駒井克昭, Kenji Shimizu

  土木学会, Nov. 2013, 土木学会論文集B2（海岸工学）, 69(2) (2), I_451 - I_455, Japanese

  [Refereed]

  Scientific journal


• 河川津波の進行・発達と河道内における変形に関する解析

  佐藤之信, 吉江祐人, NAKAYAMA KEISUKE, 柿沼太郎, 駒井克昭

  Nov. 2013, 土木学会論文集B2（海岸工学）, 69(2) (2), I_161 - I_165, Japanese

  [Refereed]

  Scientific journal


• 網走川河口における塩水遡上への吹送流の影響評価

  佐藤之信, NAKAYAMA KEISUKE, 新谷哲也, 駒井克昭

  In Abashiri River, it is demonstrated that salt-water intrusion occurs when tidal level becomes more than the lake water level. It is expected that wind driven current enhances or suppresses. It is expected that wind driven current also enhances or suppresses salt-water intrusion. This study, thus, aims to investigate the influence of wind driven current on salt-water inturion in Abashiri River by following the previous study, which reveals that easterly wind more than 4 m/s enhances salt-water intrusion. An objectoriented environmental fluid dynamics model is applied to investigate the effect of wind driven current on salt-water intrusion. As a result, easterly wind is found to suppress salt-water intrusion, which may support that radiation stress plays a great role in salt-water intrusion compared to wind driven current.

  Japan Society of Civil Engineers, Jun. 2013, 土木学会論文集B3（海洋開発）, 69(2) (2), I_1195 - I_1200, Japanese

  [Refereed]

  Scientific journal


• 東京湾スケールにおけるメッシュアスペクト比と非静水圧効果の解析

  NAKAYAMA KEISUKE, 新谷哲也, 清水健司, 木下直貴, 岡田知也, 佐藤之信, 丸谷靖幸, 駒井克昭

  In this study, we examined the validity of numerical computation by applying two different assumptions, hydrostatic and non-hydrostatic assumptions, with the change in mesh aspect ratio. Tokyo Bay was chosen as an example of an enclosed bay in order to investigate internal wave breaking over a slope. We applied 6 different mesh aspect ratios, 5, 10, 25, 50, 100 and 500. As a result, it is found from non-hydrostatic computations that the larger the aspect is, the larger the numerical error appears. In contrast to the non-hydrostatic computations, the numerical error is found to be the same in the all mesh aspect ratios. Additionally, it is revealed that mesh aspect ratio should be less than 10 in non-hydrostatic computations.

  Japan Society of Civil Engineers, Jun. 2013, 土木学会論文集B3（海洋開発）, 69(2) (2), I_709 - I_714, Japanese

  [Refereed]

  Scientific journal


• Suspended sediment transport in a river basin by using X-ray fluorescence analysis

  K. Kokubo, NAKAYAMA KEISUKE, T. Shintani, T. Ishida, Y. Maruya, K. Komai

  Jun. 2013, Asia Pacific Association of Hydrology and Water Resources (APHW 2013), 18, English

  [Refereed]

  International conference proceedings


• Hydroclimate projections for Panama in the late 21st Century

  J. Fábrega, T. Nakaegawa, R. Pinzón, NAKAYAMA KEISUKE

  This work analyzes hydroclimate projections in Panama toward the end of the 21^st century by employing the MRI-AGCM3.1 model. Understanding the impact of climate change on water resources is fundamental for a number of economic activities in Panama (i.e. Panama Canal operation, hydropower generation, and agriculture). Therefore, it is important to assess hydroclimatic impacts in specific basins using reliable Atmospheric Global Circulation Models (AGCMs) validated against actual field data. A 20-km mesh experiment was developed by using time-sliced analysis for current (1979–2002) and future (2075–2099) periods. Uncertainty in climate projections were addressed by completing 60-km mesh AGCM ensemble experiments at three additional lower boundary conditions. Four regions in Panama were selected for detailed analysis: from east to west, Bocas del Toro, Veraguas, Panama Canal and Darien. Projections show significant precipitation increases from May and July to December for all regions except Bocas del Toro. In this region, a decrease in precipitation is expected between April and August. Total runoff for all regions followed the changes in precipitation as expected. Due to net radiation increases, projected evaporation did not appear to be affected by precipitation changes.
  

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, May 2013, Hydrological Research Letters, 7(2) (2), 23 - 29, English

  [Refereed]

  Scientific journal


• 網走川河口域で発生する塩水遡上に関する数値的検討

  新谷哲也, 中山恵介

  Mar. 2013, 土木学会論文集B1（水工学）, 69(4) (4), I_829 - I_834, Japanese

  [Refereed]

  Scientific journal


• 網走湖におけるメタン発生メカニズムの解明

  丸谷靖幸, 中山恵介, 佐々木正史, 新谷哲也, 駒井克昭, 岡田知也, 菅原庸平, 崇田徳彦

  土木学会, Mar. 2013, 土木学会論文集B1（水工学）, 69(4) (4), I_1435 - I_1440, Japanese

  [Refereed]

  Scientific journal


• Design of synthetic impact response functions for flood vulnerability assessment under climate change conditions: Case studies in two selected coastal zones in Australia and Japan

  Dutta, D., Wright, W., Nakayama, K., Sugawara, Y.

  2013, Natural Hazards Review, 14(1) (1), 52 - 65, English

  [Refereed]

  Scientific journal


• Projection of "strong wind" events related to recovery from hypoxia in Tokyo Bay, Japan

  Nakayama, K., Maruya, Y., Nakaegawa, T., Komai, K., Kokubo, K., Ishida, T., Okada, T.

  2013, Hydrological Processes, 27(23) (23), 3280 - 3291, English

  [Refereed]

  Scientific journal


• INTERACTION OF SURFACE AND INTERNAL WAVES WITH VERY LARGE FLOATING STRUCTURES

  Taro Kakinuma, Kei Yamashita, Keisuke Nakayama

  2013, COASTAL STRUCTURES 2011, VOL 1 & 2, 1, 913 - 922, English

  [Refereed]

  International conference proceedings


• FUNDAMENTAL STUDY ON FLOW CHARACTERISTICS BY USING FIELD OBSERVATION IN LAKE KOMUKE

  MARUYA Yasuyuki, NAKAYAMA Keisuke, KOMAI Katsuaki, WATANABE Kenta, MIYOSHI Eiichi, ICHIMI Kazuhiko, KUWAE Tomohiro

   Lake Komuke is a typical brackish lake, which is located in the northeastern part of Hokkaido. A lot of birds, such as sipes and plovers, are well known to migrate in Lake Komuke. It is thus important to understand ecological system in Lake Komuke in order to conserve such a significant nature. Mass transport and water quality are the key factors which control ecosystem in an enclosed water body. Therefore, this study aims to clarify the characteristics of water quality and flow field. Conceptual water exchange model was applied and it is revealed that oceanic water intrudes into the lake and the change in surface water level is smaller than the tidal amplitude, which may enhance the primary production of phytoplankton in Lake Komuke.

  Japan Society of Civil Engineers, 2013, Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering), 69(2) (2), I_1228 - I_1233, Japanese

  [Refereed]

  Scientific journal


• マッハステム形成過程の数値解析

  山下啓, 柿沼太郎, 山元公, 中山恵介

  土木学会, Nov. 2012, 土木学会論文集B2（海岸工学）, 68(2) (2), I_6 - I_10, Japanese

  [Refereed]

  Scientific journal


• 振幅の違いを考慮したソリトン共鳴による大振幅ソリトンの解析

  中山恵介, 柿沼太郎, 辻英一, 及川正行

  Nov. 2012, 土木学会論文集B2（海岸工学）, 68(2) (2), I_1 - I_5, Japanese

  [Refereed]

  Scientific journal


• Shoaling of nonlinear internal waves on a uniformly sloping beach

  Yamashita K, T. Kakinuma, K. Nakayama

  Jul. 2012, Proceedings of International Conference of Coastal Engineering, 33, 1264, English

  [Refereed]

  International conference proceedings


• Nonlinear oblique interaction of large amplitude internal solitary waves

  Nakayama K, T. Kakinuma, H. Tsuji, M. Oikawa

  Jul. 2012, Proceedings of International Conference of Coastal Engineering, 33, 1053, English

  [Refereed]

  Scientific journal


• 風と塩水遡上の関連性に関する統計解析

  早川博, 加藤淳子, 中山恵介, 崇田徳彦, 中内勲, 石田哲也

  This paper describes the relationship between wind and salt wedge intrusion in Lake Abashiri. Intrusion discharge is correlated closely with water level difference between sea and lake, but may be affected in winds. This study thus aims to reveal the relationship between intrusion discharge and water level difference, wind velocity and its direction by applying statistical approaches to observed data. It shows that strong wind affects intrusion discharge secondarily by Principal Component Analysis (PCA), and observed data classified with a diagram of 1^st principal component score against 2^nd on PCA have better correlation. By multiple regression analysis with that data, estimation accuracy of intrusion discharge is improved on.

  Japan Society of Civil Engineers, Jul. 2012, 土木学会論文集B3（海洋開発）, 68(2) (2), I_745 - I_750, Japanese

  [Refereed]

  Scientific journal


• 東京湾を対象としたPartial Cell の適用性の検討

  丸谷靖幸, 吉江祐人, 中山恵介, 新谷哲也, 木下直貴, 駒井克昭, 小窪一毅, 加藤淳子

  Tokyo bay is a typical enclosed bay which has a large population on the periphery, and accumulated sludge at the seabed consumes DO, which results in hypoxia in bottom layer during summer. Because of upwelling induced by wind, hypoxia comes up to sea water surface, which may kill fish and aquatic plants. Therefore, it is needed to understand the mechanism of the occurrence and transportation of hypoxia. Previous studies have shown that there is a problem in the reproducibility with forming stepped terrain by using the cartesian coordinate system. To solve such a problem, we applied Partial Cell into sinusoidal-shape topography in the three-dimensional numerical computation. Also, Partial Cell was applied into Tokyo Bay, which shows good agreement with field observation results in terms of vertical density profile.

  Japan Society of Civil Engineers, Jul. 2012, 土木学会論文集B3（海洋開発）, 68(2) (2), I_997 - I_1002, Japanese

  [Refereed]

  Scientific journal


• 河口域における水位変化に伴う浸透流の変動機構

  駒井克昭, 川西澄, Mahdi Razaz, 小窪一毅, 渡辺聡, 中山恵介, Peter Nielsen

  Jul. 2012, 土木学会論文集B2（海岸工学）, 68(2) (2), I_1096 - I_1100, Japanese

  [Refereed]

  Scientific journal


• 内部ケルビン波の砕波により誘起される流れ

  中山恵介, 小窪一毅, 新谷哲也, 大塚淳一, 丸谷靖幸, 渡部靖憲, 駒井克昭, 岡田知也

  土木学会, Jul. 2012, 土木学会論文集B2（海岸工学）, 68(2) (2), I_926 - I_930, Japanese

  [Refereed]

  Scientific journal


• 環境流体解析のための簡易Wetting and Dryingスキーム

  新谷哲也, 中山恵介, 中本篤嗣

  Mar. 2012, 土木学会論文集B1（水工学）, 68(4) (4), I_1249 - I_1254, Japanese

  [Refereed]

  Scientific journal


• 元素分析による細粒土砂輸送割合の推定方法開発

  石田哲也, 早川博, 中山恵介, 岡田知也, 丸谷靖幸, 駒井克昭, 堀田伸之, 藤井博司, 加藤淳子

  Mar. 2012, 土木学会論文集B1（水工学）, 68(4) (4), I_637 - I_642, Japanese

  [Refereed]

  Scientific journal


• 知床を対象とした海陸の栄養塩循環機構の解明

  Aynur Abliz, 中山恵介, 丸谷靖幸, 井上徹教, 桑江朝比呂, 舘山一孝, 岡田知也, 加藤淳子, 石田哲也

  Mar. 2012, 土木学会論文集B1（水工学）, 68(4) (4), I_721 - I_726, Japanese

  [Refereed]

  Scientific journal


• Increase in simple precipitation intensity index in Panama

  K. Nakayama, C. Beitia, E. Vallester, R. Pinzon, J. Fabrega, T. Nakaegawa, Y. Maruya, J. Espinosa, B. Olmedo, J. Kato, K. Komai

  Mar. 2012, Annual Journal of Hydraulic Engineering, JSCE, 68(4) (4), I_163 - I_168, Japanese

  [Refereed]

  Scientific journal


• 極端気象現象とその影響評価に関する研究

  中山 恵介, 鬼頭 昭雄, 寶 馨, 竹内 邦良, 仲江川 敏之, 中北 英一, 山敷 庸亮

  水文・水資源学会, 2012, 水文・水資源学会研究発表会要旨集, 25, 60 - 60, Japanese


• INFLUENCE OF VELOCITY DISTRIBUTION AND DENSITY STRATIFICATION ON GENERATION OR PROPAGATION OF TSUNAMIS

  Taro Kakinuma, Kei Yamashita, Keisuke Nakayama

  2012, ADVANCES IN GEOSCIENCES VOL 28: ATMOSPHERIC SCIENCE (AS) & OCEAN SCIENCE (OS), 67 - 78, English

  [Refereed]

  International conference proceedings


• Nutrient circulation due to the interaction between terrestrial and oceanic systems

  K. Nakayama, T. Kuwae, Y. Maruya, A. Abliz, T. Inoue, K. Tateyama

  the 50th ECSA conference, 2012, The 50th Estuaries and Coastal Areas conference, O7.22, English

  [Refereed]


• Estimation of salt wedge intrusion in Kushiro wetland due to sea level rise

  A. Nakamoto, K, Nakayama,T. Shintani, Y. Maruya, T. Ishida, K. Houmura, Y. Makiguchi

  18th Congress of the Asia and Pacific Division of the International Association for Hydro-Environment Engineering and Research, 2012, Proceedings of 18th Congress of the Asia and Pacific Division of the International Association for Hydro-Environment Engineering and Research, 159 - 160, English

  [Refereed]


• INFLUENCE OF VELOCITY DISTRIBUTION AND DENSITY STRATIFICATION ON GENERATION OR PROPAGATION OF TSUNAMIS

  T. Kakinuma, K. Nakamura, K. Yamashita, K. Nakayama

  2012, PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON APAC 2011, 28, 67 - 78, English

  [Refereed]

  International conference proceedings


• Surface and Internal Waves due to a Moving Load on a Very Large Floating Structure

  Taro Kakinuma, Kei Yamashita, Keisuke Nakayama

  2012, JOURNAL OF APPLIED MATHEMATICS, 2012, 1 - 14, English

  [Refereed]

  Scientific journal


• Residual currents over a uniform slope due to breaking of internal waves in a two-layer system

  Keisuke Nakayama, Tetsuya Shintani, Kazuki Kokubo, Taro Kakinuma, Yasuyuki Maruya, Katsuaki Komai, Tomonari Okada

  Blackwell Publishing Ltd, 2012, Journal of Geophysical Research: Oceans, 117(10) (10), 1 - 11, English

  [Refereed]

  Scientific journal


• Contributions of wind and river effects on DO concentration in Tokyo Bay

  Sato, C., Nakayama, K., Furukawa, K.

  2012, Estuarine, Coastal and Shelf Science, 109, 91 - 97, English

  [Refereed]

  Scientific journal


• INFLUENCE OF VELOCITY DISTRIBUTION AND DENSITY STRATIFICATION ON GENERATION OR PROPAGATION OF TSUNAMIS

  T. Kakinuma, K. Nakamura, K. Yamashita, K. Nakayama

  2012, PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON APAC 2011, 6, TSS_07, English

  [Refereed]

  International conference proceedings


• LARGE AMPLITUDE SOLITARY WAVES DUE TO SOLITARY RESONANCE

  K. Nakayama, T. Kakinuma, H. Tsuji, M. Oikawa

  2012, PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON APAC 2011, 6, WME_09, English

  [Refereed]

  International conference proceedings


• Influence of freshwater input and bay reclamation on long-term changes in seawater residence times in Tokyo Bay, Japan

  T. Okada, NAKAYAMA KEISUKE, T. Takao, K. Furukawa

  Dec. 2011, Hydrological Processes, 24(9) (9), 2694 - 2702, English

  [Refereed]

  Scientific journal


• Evaluation of nutrient flux from Shiretoko into the ocean using MRI-GCM

  NAKAYAMA KEISUKE, A. Aynur, T. Nakaegawa, Y. Maruya

  This study aims to evaluate nutrient flux to the coast from the inland areas of Shiretoko in order to understand the key factors controlling the ecological systems of the coast. As an external force, rainfall is considered one of the most significant components controlling nutrient supply to coastal systems in this area. Therefore, to estimate nutrient supply in the future, the bias correction was applied by using Meteorological Research Institute Global Climate Model, which shows good agreement with Automated Meteorological Data Acquisition System data. A synthetic generation technique is used to produce hourly rainfall data, which is necessary for evaluating nutrient supply in Shiretoko. The robustness of the duplicated hourly rainfall intensity was investigated, which reveals that its standard deviation controls nutrient flux when nonlinearity becomes stronger for the evaluation of nutrient supply from a river basin.
  

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Dec. 2011, Hydrological Research Letters, 5, 47 - 51, English

  [Refereed]

  Scientific journal


• 東京湾における貧酸素水塊の解消要因である強風の将来予測に向けて

  丸谷靖幸, アイヌルアブリズ, 中山恵介, 仲江川敏之, 古川恵太, 駒井克明, 目淑範

  Nov. 2011, 土木学会論文集B2（海岸工学）, 67(2) (2), I_921 - I_925, Japanese

  [Refereed]

  Scientific journal


• ソリトン共鳴により発生する大振幅ソリトンの解析

  中山恵介, 柿沼太郎, 辻英一, 及川正行

  土木学会, Nov. 2011, 土木学会論文集B2（海岸工学）, 67(2) (2), I_6 - I_10, Japanese

  [Refereed]

  Scientific journal


• 薄板状浮体構造物上を移動する荷重により生成される表面波及び内部波の数値解析

  山下啓, 柿沼太郎, 中山恵介

  Jul. 2011, 土木学会論文集B3（海洋開発）, 67(2) (2), I_109 - I_114, Japanese

  [Refereed]

  Scientific journal


• 東京湾の水環境予測を目指したGCM データの利用

  Aynur Abliz, 丸谷靖幸, 中山恵介, 仲江川敏之, 古川恵太

  Jul. 2011, 土木学会論文集B3（海洋開発）, 67(2) (2), I_277 - I_282, Japanese

  [Refereed]

  Scientific journal


• 津波の生成や伝播に対する流速分布及び密度成層の影響

  柿沼太郎, 山下啓, 帖佐繁明, 藤間功司, 中山恵介

  Jul. 2011, 土木学会論文集B3（海洋開発）, 67(2) (2), I_511 - I_516, Japanese

  [Refereed]

  Scientific journal


• ANALYSIS OF MECHANISM OF WATER CIRCULATION IN KUSHIRO WETLAND FROM COMPARISONS WITH 1970S

  Y. Maruya, Y. Sugawara, A. Abliz, T. Ishida, K. Nakayama

  Japan Society of Civil Engineers, Mar. 2011, Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67(4) (4), 547 - 552, Japanese

  [Refereed]

  Scientific journal


• 降雨のインパクトによる高濁度水発生と細粒土砂輸送に関する現地観測とモデル化

  石田哲也, 中山恵介, 丸谷靖幸, 大森未音, 菅原庸平, Aynur Abliz, 上野義勝

  Mar. 2011, 土木学会論文集B1（水工学）, 67(4) (4), I_1315 - I_1320, Japanese

  [Refereed]

  Scientific journal


• 1970年代と比較した釧路湿原における水循環機構解析

  丸谷靖幸, 菅原庸平, Aynur Abliz, 石田哲也, 中山恵介

  Mar. 2011, 土木学会論文集B1（水工学）, 67(4) (4), I_547 - I_552, Japanese

  [Refereed]

  Scientific journal


• 海面上昇を考慮した釧路湿原への塩水遡上の影響評価

  中本篤嗣, 新谷哲也, 中山恵介, 丸谷靖幸, 石田哲也, 法村賢一

  Mar. 2011, 土木学会論文集B1（水工学）, 67(4) (4), I_1351 - I_1356, Japanese

  [Refereed]

  Scientific journal


• 安定同位体比による知床ラウス川を通じた海起源栄養塩の流域内分布

  Aynur Abliz, 中山恵介, 丸谷靖幸, 桑江朝比呂, 岡田知也, 石田哲也

  Mar. 2011, 土木学会論文集B1（水工学）, 67(4) (4), I_1303 - I_1308, Japanese

  [Refereed]

  Scientific journal


• Benthic and interfacial mixing in a strongly-stratified estuary

  M. Arthur Simanjuntak, Joerg Imberger, Keisuke Nakayama, Tadaharu Ishikawa

  2011, JOURNAL OF HYDRAULIC RESEARCH, 49(6) (6), 791 - 798, English

  [Refereed]

  Scientific journal


• Suspended sediment transport in a river basin estimated by chemical composition analysis

  T. Ishida, NAKAYAMA KEISUKE, T. Okada, Y. Maruya, K. Onishi, M. Omori

  Production and transportation of suspended sediment was investigated by sampling surface soils in 18 domains over an entire river basin. Particle size distributions alone suggested that all domains were a source of suspended sediment. Chemical composition analysis however showed that the transport rate of suspended sediment was more closely related to the type of surface soil than to land use. A method was developed which enables estimation of the relative suspended sediment transport rates from each domain of a river basin to its downstream end. The model's validity was verified through good agreement with field sampling results.
  

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Dec. 2010, Hydrological Research Letters, 4, 55 - 59, English

  [Refereed]

  Scientific journal


• Stochastic characterization of the onset of and recovery from hypoxia in Tokyo Bay, Japan: Derived distribution analysis based on "strong wind" events

  Keisuke Nakayama, Murugesu Sivapalan, Chizuru Sato, Keita Furukawa

  Dec. 2010, WATER RESOURCES RESEARCH, 46(12) (12), 1 - 15, English

  [Refereed]

  Scientific journal


• Residual circulation due to internal waves shoaling on a slope

  Nakayama, K., Imberger, J.

  Dec. 2010, Limnology and Oceanography, 55(3) (3), 1009 - 1023, English

  [Refereed]

  Scientific journal


• Internal waves in a two-layer system using fully nonlinear internal-wave equations

  Nakayama, K., Kakinuma, T.

  Dec. 2010, International Journal for Numerical Methods in Fluids, 62(5) (5), 574 - 590, English

  [Refereed]

  Scientific journal


• Evaluation of entrainment velocity induced by wind stress in a two-layer system

  Y. Maruya, NAKAYAMA KEISUKE, T. Shintani, M. Yonemoto

  This study aims to reveal the factors most useful for evaluating the influence of wind on entrainment from the lower to upper layer in a two-layer system. Lake Abashiri, which is a typical brackish lake, is chosen as a study area because a distinct two-layer system exists due to salt-wedge intrusion from the ocean. To evaluate entrainment velocity between two layers, a 3D numerical computation is applied, showing good agreement with field observations. Computations suggest that the entrainment velocity estimated using the Richardson number is smaller than that from field observations. Thus, other factors are computed suggesting that use of the Lake number is more effective in estimating entrainment velocity due to internal wave breaking and interfacial fluctuation than use of the Effective Wedderburn number.
  

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Dec. 2010, Hydrological Research Letters, 4, 70 - 74, English

  [Refereed]

  Scientific journal


• Applicability of 3rd Order Theoretical Solutions into Internal Waves

  K. Nakayama, T. Kakinuma, M. Oikawa, H. Tsuji, Y. Maruya

  Applicability of the 3^rd order theoretical solutions for internal waves in a two-layer system is investigated by using a strongly nonlinear and dispersive internal wave model. The 3^rd order solution is derived using the 9^th order internal wave equations. The 3^rd order solution is found to give larger wavelength scale compared to KdV theory. The applicability of the 3^rd order solution is confirmed to be high when the amplitude of internal solitary wave is 5% of the lower layer thickness. A fully nonlinear strongly dispersive internal wave model reveals that high frequency internal waves are induced behind an internal solitary wave when the initial shape of internal solitary wave is larger than critical level.

  Japan Society of Civil Engineers, Nov. 2010, Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 66(1) (1), 1 - 5, Japanese

  [Refereed]

  Scientific journal


• 塩水遡上へ与えるストークスドリフトの影響評価

  中山恵介, 丸谷靖幸, 新谷哲也, 柿沼太郎, 中内勲, 米元光明

  Nov. 2010, 海岸工学論文集, 57, 326 - 330, Japanese

  [Refereed]

  Scientific journal


• 内部ソリトン波の3次オーダ解による再現性の検討

  中山恵介, 柿沼太郎, 及川正行, 辻英一, 丸谷靖幸

  Nov. 2010, 海岸工学論文集, 57, 1 - 5, Japanese

  [Refereed]

  Scientific journal


• 深水域や砕波点近傍における非線形内部波の挙動

  山下啓, 柿沼太郎, 中山恵介, 及川正行, 辻英一, 西川学

  Nov. 2010, 海岸工学論文集, 57, 171 - 175, Japanese

  [Refereed]

  Scientific journal


• Influence of Stokes drift on salt wedge intrusion evaluated using fully-nonlinear and strongly dispersive wave equations

  Nakayama K, T. Shintani, T. Kakinuma, Y. Maruya, Y. Yonome, M. Yonemoto, I. Nakauchi

  Jul. 2010, Proceedings of International Conference of Coastal Engineering, 32, English

  [Refereed]

  Scientific journal


• 釧路湿原への塩水遡上に関する調査と検討

  中山恵介, 佐久間慎雄, 新谷哲也, 中本篤嗣, 山村諭

  Jul. 2010, 海洋開発論文集, 26, 789 - 794, Japanese

  [Refereed]

  Scientific journal


• 東京湾を対象とした内部ケルビン波の発生と砕波に関する検討

  中山恵介, 角谷和成, 新谷哲也, 清水健司, 福岡将太

  Jul. 2010, 海洋開発論文集, 26, 657 - 662, Japanese

  [Refereed]

  Scientific journal


• 融雪期における高濁度水発生機構と細粒土砂輸送

  石田哲也, 中山恵介, 大西健史, 夏井皓盛, 大森未音, アイヌルアブリズ, 丸谷靖幸, 岡田知也

  Mar. 2010, 水工学論文集, 54, 43 - 438, Japanese

  [Refereed]

  Scientific journal


• 網走湖における密度界面に対する風応力と河川流入の影響評価

  丸谷靖幸, 中山恵介, 堀松大志, 目淑範, 米元光明

  Mar. 2010, 水工学論文集, 54, 1393 - 1398, Japanese

  [Refereed]

  Scientific journal


• Extreme Weather and Impact Assessments

  Nakayama Keisuke, Kito Akio, Takara Kaoru, Takeuchi Kuniyoshi, Nakaegawa Toshiyuki, Nakakita Eichi, Yamashiki Yosuke

  極端気象現象の物理機構から影響評価までを専門とする研究者を一同に会し，防災政策に役立つような将来展望を如何に発信するかについて議論を行うことを目的とし活動を行った．主たる活動として，2009年11月5日から6日にかけて開催された，"極端気象現象とその影響評価に関する研究集会～より良い将来予測を目指して～"を挙げることが出来る．研究集会は，21世紀気候変動予測革新プログラム「極端現象予測」，京都大学防災研究所，京都大学防災研究所GCOE-ARS，土木研究所ICHARM，気象庁気象研究所，国土技術政策総合研究所との共催であった．集会では，災害から，水質，生態系システムへの影響，更には水政策や避難行動までも範疇として話題提供された．非常に国民の関心が高い気候変動予測の中でも，災害に結びつく極端現象に関する最新成果と，それを踏まえた議論は，参加者のみならず社会的にも大きな影響を与えることが期待されるものであった．

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2010, Proceeding of Annual Conference, 23, 33 - 33, Japanese


• Salt Wedge Intrusion and Stokes Drift

  NAKAYAMA Keisuke, MARUYA Yasuyuki, SHINTANI Tetsuya, KAKINUMA Taro, NAKAUCHI Isao, YONEMOTO Komei

  This paper describes the influence of surface waves on salt-wedge intrusion in terms of radiation stress. Radiation stress which includes Stokes drift effect may increase salt-wedge intrusion when surface waves propagate up a river. This study thus aims to reveal the effect of radiation stress on the distance of salt-wedge intrusion by fully nonlinear strongly dispersive internal wave equations and three-dimensional numerical computation model, Fantom3D. Fully nonlinear strongly dispersive internal wave model reveals the possibility that large radiation stress is induced near the river mouth and increases the distance of salt-wedge intrusion. Three-dimensional numerical model also demonstrates that there is a significant difference in the intrusion distance by taking into account radiation stress.

  Japan Society of Civil Engineers, 2010, PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING, 66(1) (1), 326 - 330, English


• Nonlinear Characteristics of Internal Waves in a Deep-Water Region or near a Wave-Breaking Point

  YAMASHITA Kei, KAKINUMA Taro, NAKAYAMA Keisuke, OIKAWA Masayuki, TSUJI Hidekazu, NISHIKAWA Manabu

  A set of nonlinear internal-wave equations, which have been derived on the basis of the variational principle without any assumptions concerning wave nonlinearity and dispersion, is applied to compare numerical results with experimental data of internal waves propagating in a deep-water region. Internal waves propagating over a uniformly sloping beach are also simulated. Internal progressive waves show remarkable shoaling after the interface reaches the critical level, after which the physical variables change discontinuously near the wave-breaking point. In the wave-breaking case of internal waves reflecting at a vertical wall, the vertical velocity of the particles in the vicinity of the interface is different from that of the moving interface on the wall, which means that the kinematic boundary condition on the interface is not satisfied.

  Japan Society of Civil Engineers, 2010, PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING, 66(1) (1), 26 - 30, English


• Mass transport and nutrient circulation evaluated by stable isotope analysis and chemical decomposition,

  Y. Maruya, A. Abuliz, K. Nakayama, T. Kuwae, T. Okada, T. Ishida

  5th Conference of the APHW, 2010, 5th Conference of the APHW, 428 - 435, English

  [Refereed]


• Influence of internal waves on interfacial level in Lake Abashiri

  K. Nakayama, Y. Maruya, T. Shintani, K. Shimizu, Y. Yonome, M. Yonemoto

  International Symposium on Ecohydraulics, 2010, International Symposium on Ecohydraulics 2010, 133 - 141, English

  [Refereed]


• A NUMERICAL STUDY ON PROPAGATION OF NONLINEAR INTERNAL WAVES

  Taro Kakinuma, Kei Yamashita, Keisuke Nakayama

  2010, PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON ASIAN AND PACIFIC COASTS, VOL 3, 32, 208 - +, English

  [Refereed]

  International conference proceedings


• Effect of stair-step and piecewise linear topography on internal wave propagation in a geophysical flow model

  M. A. Simanjuntak, J. Imberger, K. Nakayama

  Blackwell Publishing Ltd, Dec. 2009, Journal of Geophysical Research: Oceans, 114(12) (12), English

  [Refereed]

  Scientific journal


• Effects of spatial grid resolution on river flow and surface inundation simulation by physically based distributed modelling approach

  Dutta, D., Nakayama, K.

  Dec. 2009, Hydrological Processes, 23(4) (4), 534 - 545, English

  [Refereed]

  Scientific journal


• Effect of stair-step and piecewise linear topography on internal wave propagation in a geophysical flow model

  M. A. Simanjuntak, J. Imberger, K. Nakayama

  Dec. 2009, JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 114, 1 - 21, English

  [Refereed]

  Scientific journal


• 潜堤上における非線形内部波の伝搬特性

  柿沼太郎, 山下啓, 中山恵介

  Nov. 2009, 海岸工学論文集, 56, 66 - 70, Japanese

  [Refereed]

  Scientific journal


• Reproduction of flow over sand waves using the variation principle

  Nakayama K, T. Kakinuma, D. Horimatsu, Y. Sugawara, Y. Maruya, Y. Yonome

  Sep. 2009, River, Estuary and Coastal Morphodynamics, 6, 183 - 188, English

  [Refereed]

  Scientific journal


• A numerical study on propagation of nonlinear internal waves

  Kakinuma, T, Yamashita, K, Nakayama, K

  Jul. 2009, Proc. 5th Int. Conf. on Asian and Pacific Coasts, 3, 208 - 214, English

  [Refereed]

  Scientific journal


• 東京湾スケールの流動が京浜運河に与える影響評価

  堀松大志, 中山恵介, 岡田知也, 古川恵太, 目淑範

  Jul. 2009, 海洋開発論文集, 25, 1041 - 1046, Japanese

  [Refereed]

  Scientific journal


• 環境流体解析を目的としたオブジェクト指向型流体モデルの開発と検証

  新谷哲也, 中山恵介

  Mar. 2009, 水工学論文集, 53, 1267 - 1272, Japanese

  [Refereed]

  Scientific journal


• 斜面上での内部波の砕波形態と物質輸送

  中山恵介, 角谷和成, 古川恵太, 宮澤巧, 山敷庸亮, 丸谷靖幸

  Mar. 2009, 水工学論文集, 53, 1321 - 1326, Japanese

  [Refereed]

  Scientific journal


• 変分原理を用いた河床波上の流れの再現とその適用性

  中山恵介, 堀松大志, 柿沼太郎, 菅原庸平, 丸谷靖幸, 目淑範

  Mar. 2009, 水工学論文集, 53, 1087 - 1092, Japanese

  [Refereed]

  Scientific journal


• 網走湖における内部ケルビン波と風応力の影響評価

  中山恵介, 堀松大志, 清水健司, 丸谷靖幸, 角谷和成, 早川博, 岡田知也, 目淑範

  Mar. 2009, 水工学論文集, 53(215) (215), 1285 - 1290, Japanese

  [Refereed]

  Scientific journal


• Nonlinear Characteristics of Internal Waves Propagating over a Submerged Breakwater

  KAKINUMA Taro, YAMASHITA Kei, NAKAYAMA Keisuke

  Internal waves propagating over a submerged breakwater in a two-layer system are numerically simulated using a set of nonlinear internal-wave equations derived on the basis of a variational principle without any assumptions concerning wave nonlinearity and dispersion. When an internal-wave crest starts wave disintegration after passing over an offshore shoulder of submerged breakwater, both the horizontal velocity and dynamic pressure below the internal-wave crest show a remarkable distribution or a remarkable curvature of distribution in the vertical direction with wave dispersion. Over a submerged breakwater where the width of the breakwater crown is short or the lower-layer depth is deep over the breakwater crown, the crests of internal waves do not show wave disintegration.

  Japan Society of Civil Engineers, 2009, PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING, 65(1) (1), 66 - 70, English


• Impact of Climate Change in Coastal Areas in Kushiro Wetland

  Sugawara Yohei, Nakayama Keisuke, Yamamura Satoru

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2009, Proceeding of Annual Conference, 22, 60 - 60, Japanese


• 東京湾の湾奥底層DO濃度に対する強風イベントの統計的解析

  中山恵介, 中尾隆志, Murugesu Sivapalan, 武村圭史朗, 佐藤千鶴, 古川恵太

  Mar. 2008, 水工学論文集, 53, 193 - 198, Japanese

  [Refereed]

  Scientific journal


• Field observation and numerical simulation for Estuary Circulation and water quality in Tokyo Bay

  Yamashiki Yosuke, Kanesashi Toshiyuki, Katoh Daisuke, Takano Mariko, Fujita Yuji, Miyazawa Takumi, Nakayama Keisuke

  Field observation and numerical simulation in Tokyo Bay in 2005 and 2007 are performed using TOKYO3D and ELCOM-CAEDYM respectively. It has been observed that fresh water intrusion after the storm event does not disturb stratification in Tokyo Bay, henceforth, artificial mixing should be introduced to eliminate the Oxygen-Deficient Water.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2008, Proceeding of Annual Conference, 21, 42 - 42, Japanese


• Modeling of dissolved oxygen in an enclosed bay with sill

  T. Okada, NAKAYAMA KEISUKE

  Dec. 2007, Journal of Environmental Engineering - ASCE, 133(4) (4), 447 - 453, English

  [Refereed]

  Scientific journal


• A numerical study on internal waves induced by a typhoon around a continental shelf

  T. Kakinuma, NAKAYAMA KEISUKE

  Three-dimensional simulation of offshore currents induced by a traveling typhoon of strong winds and low pressure was performed assuming initial two-layer stratification of the sea water. The typhoon generates horizontal circulation involving divergence due to the Coriolis force, resulting in vertical circulation, which flows through the density interface. Accordingly, part of the interface is raised. The interface shows a wave train, which has the near-inertial period and propagates onshore at almost the same velocity as the passing velocity of the typhoon. The interfacial waves show their largest wave height just in front of the edge of the continental shelf, after which they separate into three components: transmitted, reflected, and orthogonal waves. The orthogonal waves turn left over the shelf edge in the northern hemisphere.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Dec. 2007, Hydrological Research Letters, 62, 574 - 590, English

  [Refereed]

  Scientific journal


• 斜面上での内部波の砕波機構と残差流

  中山恵介, 古川恵太, 宮澤功, 山敷庸亮

  This paper describest he mechanism of internalw ave breaking and its effect on the occurrence of residual currents when internal waves break over a uniform mild slope, PIV technique was applied to visualize flow field around the area where internal waves break and run up over a slope. PIV analysise nabled us to compute residual currents which revealed that undertow appears below the interface. Numerical computation was carried out using two-dimensional non-hydrostatic LES model. From the comparisons with laboratory experiment results numerical computations were confirmed to be successfully conducted with good agreements on residual currents. A bore was found from numerical computation results to have a tail which provides baroclinic energy and enhances the occurrence of down-draft

  Japan Society of Civil Engineers, Nov. 2007, 海岸工学論文集, 55, 376 - 380, Japanese

  [Refereed]

  Scientific journal


• 渦度を考慮した非線形波動方程式による表面波及び内部波の数値解析

  柿沼太郎, 中山恵介

  A functional for variational problems of multilayer-fluid systems with vorticity was presented, after which a set of nonlinear equations were derived to simulate surface and internal waves considering both strong nonlinearity and strong dispersivity of waves. The linear dispersion relations for surface and internal waves were shown also for deep-wave conditions. Stable results of surface waves propagating over a submerged breakwater, as well as internal waves reciprocating inside a closed tank, were obtained using the numerical model, where two-layer stratification was treated below a fixed horizontal plate. The internal waves resulted by the present model had a different period from that through a Boussinesq-type model. The surface waves over a slope steepened further due to the assumed vorticity effect.

  Japan Society of Civil Engineers, Nov. 2007, 海岸工学論文集, 55, 6 - 10, Japanese

  [Refereed]

  Scientific journal


• 東京湾における淡水流入量および海水の滞留時間の長期変化

  岡田知也, 高尾敏幸, 中山恵介, 古川恵太

  We calculated the monthly residence time of seawater in the inner bay of Tokyo Bay during August 2002 to June 2003 and compared it with a monthly residence time of seawater averaged from 1947 to 1974. The residence time of seawater was calculated by dividing the volume of the inner bay by an exchange rate between the inner bay and the outer bay. The exchange rate was calculated by using the monthly averaged salinity in the inner bay and the outer bay, and freshwater discharge in the inner bay. Between the years of 1947 to 1974, estimations from past studies were used to calculate the average monthly salinity. During August 2002 to June 2003, insitu salinity measurements were conducted 22 times at 27 stations within Tokyo Bay. The freshwater discharge into the inner bay was calculated from the catchment area precipitation and water mass imported from the neighboring catchment area for both data sets. From the results, the residence time of seawater during 2002 consisted of an annual mean of 31 days, with seasonal residence times of 19 days during summer and 43 days during winter. On the other hand, during 1947-1974, the mean annual residence time of seawater was 48 days, with summer and winter seasonal durations of 28 days and 79 days respectively. Thus seawater residence time in the inner bay during 2002 was greatly reduced them previous long-term estimations, by approximately 35%.

  Japan Society of Civil Engineers, Nov. 2007, 土木学会論文集, 63(1) (1), 67 - 72, Japanese

  [Refereed]

  Scientific journal


• アオコ流動モデルを用いた天竜川の藍藻Microcystis細胞濃度の時間変動予測

  片上幸美, 中山恵介, 横山淳史, 本間隆満, 朴虎東

  Nov. 2007, 陸水学会誌, 68(2) (2), 241 - 251, Japanese

  [Refereed]

  Scientific journal


• 東京湾奥における底層DOに対する風および河川流入の影響評価

  中山恵介, 佐藤千鶴, 古川恵

  A conceptual DO model was developed to investigate the influence of wind and rain on the dissolved oxygen concentration around the head of Tokyo Bay. Since the DO concentration in the lower layer around the bay head has been revealed to be predominantly controlled by estuarine circulation, the effect of rain and wind on estuarine circulation was included in the conceptual DO model. The conceptual DO model, thus, consists of the following five components. (1) DO consumption at sea bottom; (2) Estuarine circulation due to stratification; (3) Change in estuarine circulation due to wind; (4) Change in estuarine circulation due to inflow from rivers; and (5) Sweep effect due to strong wind. To clarify the effect of inflow from rivers, it is needed to estimate river discharge from rainfall intensity in terms of runoff model. In this study, we decided to use a linear storage function model so that it enables us to evaluate the influence of rain on DO concentration around the bay head theoretically. Partitioning triangle method was introduced, which makes us understand the contribution of each component easily. And also, the significance of river discharge effect was revealed on the recovery of the DO concentration.

  Japan Society of Civil Engineers, Jul. 2007, 海洋開発論文集, 24, 633 - 638, Japanese

  [Refereed]

  Scientific journal


• 芝浦運河 海の顔・川の顔調査

  佐藤千鶴, 古川恵太, 中山恵介

  Shibaura canal connects with the ocean through two sluices and receives major inflows of sewage disposal water. Therefore, it is a typical urban brackish water area with a presumably complex flow pattern. In addition, Shibaura canal is among those regions where the local residents are environmentally conscious. In order to clarify the water flow characteristic in Shibaura canal and to develop an observation method of public participation, in this study, field observations were made using a simple float with a drag board on the flood tide on 28 May 2006 "Umi-no-kao (color of sea) "and on the ebb tide on 16 July 2006"Kawa-no-kao (color of river) ". To verify these results, we performed three-dimensional model calculations. The field observations and numerical computations show public participation using a simple float is useful and easy way to determine the flow pattern in urban brackish water area.

  Japan Society of Civil Engineers, Jul. 2007, 海洋開発論文集, 24, 763 - 768, Japanese

  [Refereed]

  Scientific journal


• Development of a conceptual model for dissolved oxygen concentrations considering flood event effects in Tokyo Bay

  C. Satoh, K. Nakayama, Y. Yamashiki, T. Kanasashi, K. Miyazawa

  This paper proposes a method to evaluate the occurrence of anoxic water in Tokyo Bay, which is a typical enclosed bay in Japan. In Tokyo Bay, seawater exchange with the ocean is revealed to be dominantly controlled by estuarine circulation. Dissolved oxygen (DO) concentrations in the bay head are, thus, expected to be influenced by estuarine circulation. The strength of estuarine circulation changes owing to wind and inflow from rivers. Therefore, we investigated the influence of inflow from rivers on DO concentration around the bay head by using a three-dimensional ecological model. To evaluate the occurrence of anoxic water, we developed a conceptual DO model which was verified through good agreement with the results from a three-dimensional ecological model. As a result, the conceptual DO model has potential in the evaluation of the occurrence of anoxic water around the head of Tokyo Bay.

  Japan Society of Civil Engineers, Mar. 2007, Annual Journal of Hydraulic Engineering, JSCE, 52, 199 - 204, Japanese

  [Refereed]

  Scientific journal


• Numerical simulation of internal waves using a set of fully nonlinear internal-wave equations

  T. Kakinuma, K. Nakayama

  Internal waves in a two-layer system are simulated using a set of fully nonlinear internal-wave equations, which was derived on the basis of a variational principle without any assumptions of wave nonlinearity and dispersivity. Computational results of interface displacements up to each order on the vertical length scale of motion are compared with calculation results obtained using a Boussinesq-type internal-wave model or the existing experimental data. In a long-wave case, interface displacements obtained by the proposed model with more than two vertically distributed functions of velocity potential are in harmony with those by the Boussinesq-type model, as well as the experimental data especially in the wave number. In an intermediate-wave case, the present model shows different results from those through the Boussinesq-type model, which should not be applied to this case without enough consider- ation of the wave dispersivity.

  Japan Society of Civil Engineers, Mar. 2007, Annual Journal of Hydraulic Engineering, JSCE, 52, 169 - 174, Japanese

  [Refereed]

  Scientific journal


• 一様な斜面上で砕波する内部ケルビン波により誘起される流れ

  中山恵介, 宮澤巧, 山敷庸介, 宮澤兼佑, 金刺俊之

  This paper describes influence of internal Kelvin wave breaking over a uniform slope on mass transport and mixing. A rotating tank, whose length and width are 6 m and 0.4 m, was used to investigate fundamental characteristics of internal Kelvin waves with and without a uniform slope. The theoretical solution of internal Kelvin waves including the friction effect was derived, which agrees with the laboratory experiment results. Energy dissipation due to the friction effect was evaluated using the viscous boundary theory, which reveals that the rate of energy dissipation is larger in the case with the Coriolis effect rather than without the Coriolis effect. Density flux measurements revealed that cyclonic circulation appears when internal Kelvin waves propagate and break over a uniform slope.

  Japan Society of Civil Engineers, Mar. 2007, 水工学論文集, 52, 1385 - 1390, Japanese

  [Refereed]

  Scientific journal


• Density intrusion and variation in dissolved oxygen concentrations in a bay with a sill at its mouth

  Okada, T., Nakayama, K.

  2007, Journal of Environmental Engineering, 133(4) (4)

  Scientific journal


• Analysis of Flow Field with High-resolution in Tokyo Bay~Reproduction of DO Concentration in Tokyo Bay in Measurements Line of the Tama River offing,2006~

  kanesashi toshiyuki, yamashiki yousuke, miyazawa takumi, satou chiduru, nakayama keisuke

  The effect of Tama river inflow into Tokyo Bay on dissolved oxygen in bottom layer has been analyzed using numerical simulation by ELCOM- CAEDYM and field observation. The result implied that the Tama River inflow may contribute the decrease of dissolved oxygen, however further evaluation should be made for further evaluation.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2007, Proceeding of Annual Conference, 20, 88 - 88, Japanese


• A numerical study on stratified flows induced by a typhoon in a bay and around a continental shelf

  Taro Kakinuma, Keisuke Nakayama

  2007, ASIAN AND PACIFIC COASTS 2007, 5, 295 - +, English

  [Refereed]

  International conference proceedings


• Numerical study on the flow characteristics of tidal jets induced by a tidal-jet-generator

  J. C. Parka, T. Okada, K. Furukawa, NAKAYAMA KEISUKE

  Dec. 2006, Ocean Engineering, 33(14) (14), 1896 - 1918, English

  [Refereed]

  Scientific journal


• Comparisons of CIP, compact and CIP-CSL12 schemes for reproducing internal solitary waves

  Nakayama, K.

  Dec. 2006, International Journal for Numerical Methods in Fluids, 51(2) (2), 197 - 219, English

  [Refereed]

  Scientific journal


• 2003年東京湾に発生した繊毛虫Mesodinium rubrumによる赤潮と水生生物の大量死の連関に関する調査事例

  古川恵太, 中山恵介, 水尾寛己

  日本沿岸域学会, Dec. 2006, 沿岸域学会論文集, 18(4) (4), 67 - 77, Japanese

  [Refereed]

  Scientific journal


• 台風により大陸棚近傍に生成される内部波の数値解析

  柿沼太郎, 中山恵介

  外洋遠方から進行する台風が, 大陸棚を通過して沿岸域に接近する場合の, 海水密度流の3次元数値解析を行なった. 表層内の水平渦流が鉛直循環流を伴い, その結果, 界面の上昇が生じた. 台風の中心より後方に最高水位が, その後方に水平渦流の中心が位置し, 界面は, 更に後方で上昇した. 界面の上昇位置は, 大陸棚外縁に至るまで台風に追従し, 内部界面の高まりは, 大陸棚外縁から外洋までの広水域に及んだ. 内部波は, 大陸棚外縁近傍で, 初期上層水深が深いほど大きな最大波高を示した後, 透過波・反射波成分と, 大陸棚外縁に沿って進む成分とに分離した. この最大波高に対する大陸棚上の内部波波高の比は, 大陸棚上の下層水深が深いほど高くなった.

  Japan Society of Civil Engineers, Nov. 2006, 海岸工学論文集, 53, 361 - 365, Japanese

  [Refereed]

  Scientific journal


• 東京湾における季節特性を考慮した湾内流動の再現計算

  五十嵐学, 中山恵介

  This study describes typical mass transports in spring, summer, autumn and winter in Tokyo Bay by using a non-hydrostatic model, MEL3D. Some typical salinity and water temperature distributions in each season obtained from field observation were used in the numerical computation. Furthermore, spatial distributions of wind over Tokyo Bay evaluated using nine meteorological observation stations were applied in the computation as boundary conditions. To investigate mass transport, neutral particle tracking simulations were carried out by putting particles along near the coastal line by about 4km. As the results, especially in summer, it was demonstrated that the characteristic of the neutral particle transport in Tokyo Bay is strongly affected by the vertical current of circulation around the western coast in the head of Tokyo Bay.

  Japan Society of Civil Engineers, Jul. 2006, 海洋開発論文集, 22, 829 - 834, Japanese

  [Refereed]

  Scientific journal


• 湾口部にシルをもつ湾における底層貫入とDO濃度に関する観測と数値実験

  中山恵介, 岡田知也

  This paper describes density intrusion which influences water quality in Ohfunato Bay. Field experiments were carried out to directly measure the change in the DO concentration and velocity due to density intrusion which appears over a sill around the bay mouth. As suggested in the previous studies, it is found from the field experiments that density intrusion occurred during the flood tide and the DO concentration on the seabed is greatly influenced by the density intrusion since the high DO concentration water can be brought into the deep water region by the density intrusion. A non-hydrostatic three-dimensional LES model was used to analyze the effect of the density intrusion. The computation was verified from the comparison with the observed velocity. It is revealed from the computation that the front of the density intrusion can rapidly propagate into the seabed around the centre of the bay and the density intrusion may change the DO concentration on the seabed in a few hours.

  Japan Society of Civil Engineers, Jul. 2006, 海洋開発論文集, 22, 817 - 822, Japanese

  [Refereed]

  Scientific journal


• 東京湾奥における出水時の河川水挙動に関する基礎的研究

  西田有佑, 中山恵介, 石川忠晴

  It is necessary to grasp the behavior of the river water which gives pollution load, because of the design of the water quality improvement policy of Tokyo Bay where the deterioration advances. So this paper examined the flow characteristic of river water around the head of the Tokyo Bay in the flood using numerical simulation and satellite image. First, the pattern of advective diffusion of the river water was caught from LANDSAT image, and second it was simulated numerically by MEL3D which is a three-dimensional model. As the result, flow pattern of the surface layer which has appeared in the satellite image was recreated well with MEL3D. Finally, the relationship between hydrologic and meteorologic condition and behavior of river water was examined by the calculate condition systematically changing, it was shown that the flow of surface which is generated by the wind around the head of Tokyo Bay influenced the advective diffusion of the river water.

  Japan Society of Civil Engineers, Jul. 2006, 海洋開発論文集, 22, 793 - 798, Japanese

  [Refereed]

  Scientific journal


• 河口部に設置された円柱による河口周辺での乱れエネルギーに関する検討

  中山恵介, 岡田知也, 古川恵太

  Mar. 2006, 水工学論文集, 50, 1387 - 1392, Japanese

  [Refereed]

  Scientific journal


• Circulation processes in Tokyo Bay

  Nakayama, K.

  2006, The Environment in Asia Pacific Harbours

  Scientific journal


• 円柱による乱れが河口の塩水侵入に与える影響評価

  中山恵介, 岡田知也, 古川恵太

  2006, 水工学論文集, 50, 1378 - 1392


• Mechanism responsible for fortnightly modulations in estuarine circulation in Tokyo Bay

  Nakayama, K., Okada, T., Nomura, M.

  Dec. 2005, Estuarine, Coastal and Shelf Science, 64(2-3) (2-3), 459 - 466, English

  [Refereed]

  Scientific journal


• 強風の吹き寄せにより密度成層水域に生成する流れ場の 3 次元数値計算

  柿沼太郎, 中山恵介

  強風の吹き寄せ効果に着目して, 密度分布を有する水域を対象とした数値解析を行ない, 台風の来襲前から通過後にわたる期間の水位, 流速及び密度の変化過程について調べた. 密度が単一である場合, または, 初期密度が2層に成層している場合について, 3次元計算を行なった. 矩形湾内に密度分布がある場合, 湾幅に依存する内部波モードの現象が現れること, また, 岬前面において, 水位が湾奥よりも低くなり, 低密度水が中層に潜り込むこと, そして, 東京湾において強風による拘束が弱まり始めると, 吹き寄せによって形成された密度分布に起因する海水流動が発生し, 台風通過後もそれが暫く継続することが確かめられた.

  Japan Society of Civil Engineers, Nov. 2005, 海岸工学論文集, 52, 306 - 310, Japanese

  [Refereed]

  Scientific journal


• 斜面に連続的に作用する内部界面の理論解の適用性の検討

  中山恵介, Jorg Imberger

  Nov. 2005, 土木学会論文集, 789, 59 - 71, Japanese

  [Refereed]

  Scientific journal


• 河道モデルと沿岸流動モデルの統合とその必要性に関する検討

  中山恵介, Dushmanta Dutta, 田中岳, 岡田知也

  Nov. 2005, 水文水資源学会誌, 18(4) (4), 390 - 400, Japanese

  [Refereed]

  Scientific journal


• Modeling the effect of stratification on sediment deposition

  Nakayama K

  Sep. 2005, River, Estuary and Coastal Morphodynamics, 4, 1027 - 1034, English

  [Refereed]

  Scientific journal


• 東京湾における散逸率の縦断分布と鉛直混合

  中山恵介, 岡田知也

  This paper describes the investigation of dissipation and vertical mixing in an enclosed bay, Tokyo Bay. The field experiment was carried out on 17^th of November, 2004 along the longitudinal section of Tokyo Bay to measure water temperature, salinity, turbidity and micro-structure of turbulence. It was revealed from vertical density distribution, which was identified by salinity and water temperature, and vertical turbidity distribution that either large velocity due to internal waves or mixing due to internal wave breaking caused resuspension of seabed sediment. Dissipation obtained from field experiment agreed well with those from numerical simulation. This may thus provide evidence that turbulent closure scheme used in the numerical simulation is valid to model flow fields in Tokyo Bay.

  Japan Society of Civil Engineers, Jul. 2005, 海洋開発論文集, 21, 379 - 384, Japanese

  [Refereed]

  Scientific journal


• 東京湾の湾奥における時計回りの循環と収束現象の解明

  中山恵介, 芝口芳行, 日向博文, 石川忠晴

  Clockwise circulation in the upper layer and the decrease in the level of interface were found from field experiments to occur around the head of Tokyo Bay on 10th August 2001. It was revealed that the clockwise circulation in the upper layer resulted from wind with clockwise vorticity around the bay head, which appears when the dominant north or north-easterly wind changed to south-westerly. To clarify the mechanism responsible for the decrease in the level of interface, numerical experiment was carried out by using non-hydrostatic three-dimensional model (MEL3D). The importance of the sea-bottom slope around the bay head and clockwise circulation in the upper-layer was demonstrated.

  Japan Society of Civil Engineers, Mar. 2005, 水工学論文集, 49, 1297 - 1302, Japanese

  [Refereed]

  Scientific journal


• 東京湾湾口部におけるフロント形成過程の究明

  中山恵介, 清木荘一郎, 石川忠晴, Alex S.J. Wyatt

  This paper describes the occurrence of the front around the head of Tokyo Bay. Salinity, temperature and ADCP measurements were performed in Tokyo Bay during a spring tide on 21st November 2002. It was revealed the estuary circulation was suppressed and the down-welling appeared as a result of the front during the spring tide. Numerical computations were used to clarify the mechanism responsible for the front. A non-hydrostatic three-dimensional model (MEL3D) demonstrated the front at the bay mouth for a case when large tidal amplitude coincided with weak stratification. A two-dimensional two-layer model was used to confirm whether the stability of interface due to flow is significant for the occurrence of the front. As a result, the change in water depth and width are significant for the occurrence of the front in terms of the two-layer model.

  Japan Society of Civil Engineers, Mar. 2005, 水工学論文集, 49, 1291 - 1296, Japanese

  [Refereed]

  Scientific journal


• A Comparative Analysis of River Flow Modeling in an Urban River Basin in Japan Using Lumped and Physically Based Approaches

  Keisuke Nakayama, Dutta Dushmanta, Gaku Tanaka, Fathanha Khanam

  2005, MTERM International Conference, 207 - 214, English

  [Refereed]

  International conference proceedings


• 固定グリッドにおいて遡上波を追跡する計算手法の開発

  中山恵介, 工藤健太郎, 石川忠晴

  Nov. 2004, 海岸工学論文集, 51, 16 - 20, Japanese

  [Refereed]

  Scientific journal


• 荒川河口域における潮差変動に伴うChlorophyll a分布および河川流入負荷量の変動

  岡田知也, 中山恵介

  The purpose of this study is to clarify the relationship amongst tidal range, distribution of Chlorophyll a and phosphorus flux around the mouth of the Arakawa River. We observed the phytoplankton bloom occurred around the density front during the spring tide when a moderately mixed estuary appeared. Conversely, the phytoplankton bloom occurred thinly under the halocline during the neap tide when a fully stratified estuary appeared. A three-dimensional hydrostatic model was used to better understand the mechanism of the change in Chlorophyll a distribution and phosphorus flux due to tidal range. Additionally, the phosphorus flux around the mouth of the river during the neap tide was found to be twice as large as during the spring tide. Therefore, it appears that the mouth of the river where the stratification strength changes with tidal range has a role of buffer against the phosphorus load.

  Japan Society of Civil Engineers, Nov. 2004, 土木学会論文集, 754(754) (754), 33 - 50, Japanese

  [Refereed]

  Scientific journal


• 2002年東京湾の海水の滞留時間とマルチボックス鉛直1次元モデルを用いた再現計算

  高尾敏幸, 岡田知也, 中山恵介, 古川恵太

  Mar. 2004, 水工学論文集, 48, 1243 - 1248, Japanese

  [Refereed]

  Scientific journal


• 高瀬川の浅瀬が塩水遡上に与える影響について

  和光一紀, 中山恵介, 石川忠晴

  Mar. 2004, 水工学論文集, 48, 793 - 798, Japanese

  [Refereed]

  Scientific journal


• 2成層場におけるソリトンに対する新たなスキームの適用と検討

  中山恵介

  Mar. 2004, 水工学論文集, 48, 1219 - 1224, Japanese

  [Refereed]

  Scientific journal


• 移流拡散モデルを用いた天竜川の藍藻Microcystisの動態解析

  片上幸美, 中山恵介, 金昊燮, 米塚佐代子, 朴虎東

  Nov. 2003, 陸水学会誌, 64(2) (2), 121 - 131, Japanese

  [Refereed]

  Scientific journal


• 有限要素CIP-mスキームを用いた流況予測シミュレーション

  中山恵介, 森下正志, 岡田知也

  Nov. 2003, 計算工学講演会論文集, 8(2) (2), 1 - 4, Japanese

  [Refereed]

  Scientific journal


• 斜面に連続的に作用する内部波の砕波と残差流

  中山恵介, Jorg Imberger

  本研究は, 斜面に連続的に作用する内部波により生じる残差流としての鉛直循環について検討することを目的とする.過去に行われた実験結果を利用して, CarrierとGreenspanにより提案されている弱非線形方程式である長波近似された方程式の解を砕波する際の内部波に適用し, その適用性を検討した. 理論解による残差流は, 実験との比較により良好な再現性を示していることが分かった.これにより, Bp=7～8程度の場合, 内部波の砕波は3次元的な現象ではあるが, 鉛直積分された2層流方程式を用いても, 比較的良好に内部波の斜面上での砕波による流れ場を再現できることが分かった.

  Japan Society of Civil Engineers, Nov. 2003, 海岸工学論文集, 50, 141 - 145, Japanese

  [Refereed]

  Scientific journal


• 荒川河口域にけるChl-aの鉛直分布

  岡田知也, 中山恵介

  2002年の7月から9月にかけて, 荒川河口域において, 河川域から沿岸域に拡がるChl-aおよび栄養塩の鉛直分布の流軸方向変動に対して調査を実施した. 河口域におけるChl-a鉛直分布は表層よりも中層に高濃度域が発達する特徴をもつ. この傾向は河口域の混合形態が弱混合に近い場合の方が顕著である. このことは, 数値モデルによる解析によって, 混合形態が生産力に与える影響よりも, 混合形態に伴う, 河口域での滞留時間が影響を及ぼしていると推測された.

  Japan Society of Civil Engineers, Nov. 2002, 海岸工学論文集, 49, 1021 - 1025, Japanese

  [Refereed]

  Scientific journal


• 総合的内湾水質評価モデルの構築と東京湾への適用

  岡田知也, 中山恵介, 宮野仁, 古川恵太

  Nov. 2002, 海岸工学論文集, 49, 1051 - 1055, Japanese

  [Refereed]

  Scientific journal


• 二枚貝が優占する湖沼の水塊形成に関する数値解析

  中村由行, 奥宮英治, 中山恵介

  浅い沿岸部に二枚貝が生息する宍道湖を対象として, 熱及び風に起因する水塊構造の形成に関する解析を行った. 三次元乱流モデルに基づく湖流解析モデルに, 日周期の風速及び水面熱収支の変動を与えて計算を行った. その結果, 湖の北岸側に冷水塊が発達し, 水温構造に南北非対称性が生じた. この非対称性は湖底地形に起因するが, 夏季に典型的な西風は非対称性を強化することが見出された. 計算の水温分布は観測値を良く再現すること, 栄養塩濃度分布は水温と相似な分布を取る事から, 水温構造が湖沼の物質循環やシジミ生息域の分布にも密接に関わっている事が示唆される.

  Japan Society of Civil Engineers, Nov. 2002, 海岸工学論文集, 49, 1031 - 35, Japanese

  [Refereed]

  Scientific journal


• 湖沼の平面的な水塊分布構造に及ぼす水表面熱収支の影響

  中村由行, 奥宮英治, 中山恵介

  Japan Society of Civil Engineers, Nov. 2001, 海岸工学論文集, 48, 1051 - 1055, Japanese

  [Refereed]

  Scientific journal


• 夏期の東京湾湾奥における表層の植物プランクトンに対する底層栄養塩の影響

  岡田知也, 中山恵介, 野村宗弘, 古川恵太

  Nov. 2001, 海岸工学論文集, 48, 1086 - 1090, Japanese

  [Refereed]

  Scientific journal


• 内湾における環境問題の展開と環境シミュレーション

  古川恵太, 岡田知也, 中山恵介, 細川恭史

  Nov. 2001, 海洋工学シンポジウム, 16, 43 - 48, Japanese

  [Refereed]

  Scientific journal


• 内湾の環境評価を目指したMEL1D-MBモデルの構築と東京湾への適用

  中山恵介, 岡田知也, 宮野仁, 古川恵太

  Nov. 2001, 海洋工学シンポジウム, 16, 59 - 66, Japanese

  [Refereed]

  Scientific journal


• 融雪を考慮した山地流出モデルに関する研究

  中山恵介, 伊藤哲, 藤田睦博, 斎藤大作

  Run-off analysis taking into account physical processes have been able to be carried out due to sophisticated computers. River basin is formed by a flow in a river channel, an infiltration flow and a groundwater flow that have different hydraulic characters. In order to pay attention to run-off analysis in a mountainous river, an infiltration flow model and a river flow model were proposed by using an unsaturated infiltration flow theory and a turbulent closure model, respectively. A whole basin was covered with rectangular grids and computations were carried out by finite difference method. Moreover, to carry out a long-term simulation during a thaw period, a snow-melting model was introduced by using heat budget equation. Run-off simulations were carried out in summer and a thaw period, and in both cases, good agreements were obtained even in long-term simulations.

  Japan Society of Civil Engineers, Nov. 2001, 土木学会論文集, 691(691) (691), 25 - 41, Japanese

  [Refereed]

  Scientific journal


• Internal wind waves and snow clouds on a mountain slope

  K. Nakayama, D. Saitoh

  Nov. 2001, Journal of Hydroscience and Hydraulic Engineering, 19(2) (2), 105 - 117, English

  [Refereed]

  Scientific journal


• 東京湾湾奥部におけるChl-a(植物プランクトン量)空間分布評価モデルに関する検討

  岡田 知也, 中山 恵介, 野村 宗弘

  国土交通省港湾技術研究所, Jun. 2001, 港湾技研資料, (1003) (1003), 1 - 21, Japanese


• 閉鎖性内湾の底層溶存酸素濃度に対する湾口防波堤の影響

  岡田 知也, 中山 恵介, 宮野 仁

  国土交通省港湾技術研究所, Jun. 2001, 港湾技研資料, (1004) (1004), 1 - 15, Japanese


• 界面渦等により不連続化した流れ場再現プログラムCIP-m-FEMの開発

  中山 恵介, 岡田 知也

  国土交通省港湾技術研究所, Mar. 2001, 港湾技研資料, (989) (989), 1 - 15, Japanese


• 湖沼の物質循環に及ぼす夜間の水面冷却の影響

  奥宮英治, 中村由行, 中山恵介, 井上徹教, 石飛裕

  Mar. 2001, 水工学論文集, 45, 1147 - 1152, Japanese

  [Refereed]

  Scientific journal


• 常射流混在場における有限要素CIP-mスキームの構築

  中山恵介, 森下正志, 岡田知也, 古川恵太, 安原晃, 中村裕一

  Internal waves in a bay have an effect on vertical mixing and mass transfer. Toestimate sources and roles of the internal waves, we have to carry out computation with high resolution by using a three-dimensional non-hydrostatic model. As it is hard to carry out it now, a multi-layer model is considered to be one of the most suitable model. However, internal hydrolic jumps occur frequently on an interface between layers because of small density difference and great velocity (Internal Froude number>1.0). In previous studies, a flow field including both rapid and streaming flow has been solved by CIP-m scheme in which a finite difference method is used. But it is better to use a finite difference method (FEM) because the shape of a bay are complicated and FEM can be applied to any shape. In this study our purpose is to develop CIP-m FEM. The result of an experiment was consistent with that of computation.

  Japan Society of Civil Engineers, Mar. 2001, 水工学論文集, 45, 595 - 600, Japanese

  [Refereed]

  Scientific journal


• 大船渡湾における底層DO濃度の変動に及ぼす湾外の影響

  岡田知也, 中山恵介, 日比野忠史, 細川恭史, 古川恵太

  Japan Society of Civil Engineers, Nov. 2000, 海岸工学論文集, 47, 1041 - 1045, Japanese

  [Refereed]

  Scientific journal


• 大潮, 小潮期における湾外水の影響

  中山恵介, 岡田知也, 野村宗弘, 日比野忠史, 細川恭史, 古川恵太

  Nov. 2000, 海岸工学論文集, 47, 421 - 425, Japanese

  [Refereed]

  Scientific journal


• 内湾域の水環境に影響を及ぼす物理的要因に関する考察-瀬戸内海総合水質調査データによる解析-

  宮野仁, 日比野忠史, 中山恵介, 岡田知也, 細川恭史, 浅井正, 日比野 忠史

  国土交通省港湾技術研究所, Jun. 2000, 港湾技術研究所報告, 39(2) (2), 47 - 72, Japanese

  [Refereed]

  Scientific journal


• 大船渡湾における湾外水の密度変動が湾内水環境に及ぼす影響の定量的評価

  岡田知也, 中山恵介, 日比野忠史, 細川恭史, 日比野 忠史

  国土交通省港湾技術研究所, Jun. 2000, 港湾技術研究所報告, 39(2) (2), 73 - 98, Japanese

  [Refereed]

  Scientific journal


• 湾内外の密度差による湾口部での流出入機構

  日比野忠史, 岡田知也, 中山恵介

  Mar. 2000, 水工学論文集, 44, 945 - 950, Japanese

  [Refereed]

  Scientific journal


• 樹林群を考慮した浅水流モデル

  中山恵介, 堀川康志, 江島敬三

  Mar. 2000, 水工学論文集, 44, 801 - 806, Japanese

  [Refereed]

  Scientific journal


• 成層場における固液混相流LESモデルの開発

  中山恵介

  Mar. 2000, 水工学論文集, 44, 879 - 884, Japanese

  [Refereed]

  Scientific journal


• 東京湾における成層期の流れ場

  日比野忠史, 中山恵介, 岡田知也

  土木学会, Mar. 2000, 水工学論文集, 44, 1056 - 1060, Japanese

  [Refereed]

  Scientific journal


• Simulation of Kanmon Strait; A channel between two seas

  Mohamed Elzeir, Tadashi Hibino, Keisuke Nakayama

  2000, Coastal Engineering 2000 - Proceedings of the 27th International Conference on Coastal Engineering, ICCE 2000, 276, X3861 - 3869, English

  [Refereed]

  International conference proceedings


• Cold air flow and simulation of snow clouds

  K. Nakayama, K. Hasegawa, M. Fujita

  Dec. 1999, Journal of Hydroscience and Hydraulic Engineering, 17(2) (2), 127 - 138, English

  [Refereed]

  Scientific journal


• LESモデルによる水平面上張り出しプルームの解析

  中山恵介, 佐藤圭洋

  Nov. 1999, 土木学会論文集, 628, 97 - 114, Japanese

  [Refereed]

  Scientific journal


• 射流場におかれた円柱周辺の流れの解析

  中山恵介, 堀川康志, 三上卓哉

  Mar. 1999, 水工学論文集, 43, 365 - 370, Japanese

  [Refereed]

  Scientific journal


• 矩形グリッドを用いた山地流出解析

  中山恵介, 伊藤哲, 藤田睦博

  Mar. 1999, 水工学論文集, 43, 31 - 36, Japanese

  [Refereed]

  Scientific journal


• 内部波が山地斜面の大気に及ぼす影響

  中山恵介, 斎藤大作

  Mar. 1999, 水工学論文集, 43, 257 - 262, Japanese

  [Refereed]

  Scientific journal


• A study on a wind field when a cold air flow that causes snowfall around Sapporo

  K. Nakayama, K. Hasegawa, M. Fujita

  Dec. 1998, Journal of Hydroscience and Hydraulic Engineering, 16(1) (1), 9 - 25, English

  [Refereed]

  Scientific journal


• A numerical study on a cold air flow causing the formation of snow clouds over Sapporo City

  K. Nakayama, K. Hasegawa, M. Fujita

  Dec. 1998, Journal of Hydroscience and Hydraulic Engineering, 16(2) (2), 35 - 48, English

  [Refereed]

  Scientific journal


• 冬期石狩湾における陸からの冷気流フロント上に発生する降雪雲観測

  中山恵介, 長谷川和義, 藤田睦博

  Nov. 1998, 土木学会論文集, 593(593) (593), 1 - 10, Japanese

  [Refereed]

  Scientific journal


• 降雪をともなう冷気流に関する実験および数値計算予測

  中山恵介, 中嶌一彦, 長谷川和義, 藤田睦博

  Nov. 1998, 土木学会論文集, 607(607) (607), 1 - 17, Japanese

  [Refereed]

  Scientific journal


• 陸から海上へ張り出す冷気流と雪雲発生予測に関する研究

  中山恵介, 長谷川和義, 藤田睦博

  Mar. 1998, 水工学論文集, 42, 31 - 36, Japanese

  [Refereed]

  Scientific journal


• CIP法を用いた浅水流方程式の数値計算手法の開発

  中山恵介, 佐藤圭洋, 堀川康志

  Mar. 1998, 水工学論文集, 42, 1159 - 1164, Japanese

  [Refereed]

  Scientific journal


• 全流域を矩形グリッドで覆いSGS効果を考慮した浸透流方程式を用いた流出予測

  中山恵介, 伊藤哲

  Mar. 1998, 水工学論文集, 42, 1141 - 1146, Japanese

  [Refereed]

  Scientific journal


• 雪雲発生要因である冷気流に関する数値実験的研究

  中山恵介, 中嶌一彦, 長谷川和義, 藤田睦博

  Mar. 1997, 水工学論文集, 41, 19 - 134, Japanese

  [Refereed]

  Scientific journal


• 冬期石狩湾において豪雪をもたらす冷気流張り出しに関する研究

  中山恵介, 長谷川和義, 藤田睦博

  Nov. 1996, 土木学会論文集, 539, 31 - 42, Japanese

  [Refereed]

  Scientific journal


• 札幌周辺に豪雪をもたらす冷気流発生時における風の場に関する研究

  中山恵介, 長谷川和義, 藤田睦博

  Mar. 1996, 水工学論文集, 40, 267 - 272, Japanese

  [Refereed]

  Scientific journal


• 冬期石狩湾における鉛直断面内の冷気流形状に関する研究

  中山恵介, 長谷川和義, 藤田睦博

  Mar. 1995, 水工学論文集, 39, 177 - 182, Japanese

  [Refereed]

  Scientific journal


• ANALYSIS OF WIND FIELDS IN WINTER BY USING AMEDAS AND CONSIDERING TOPOGRAPHY

  K NAKAYAMA, K HASEGAWA

  1994, SNOW AND ICE COVERS: INTERACTIONS WITH THE ATMOSPHERE AND ECOSYSTEMS, (223) (223), 177 - 186, English

  [Refereed]

  International conference proceedings

• Experiment of Absorption of Dissolved Organic Carbon due to Senninmo and Marimo

  寺田惇哉, 駒井克昭, 尾山洋一, 中山恵介, 倉本祥吾

  2024, 土木学会北海道支部論文報告集(CD-ROM), (80) (80)


• IMPACT OF EELGRASS ON CARBON CAPTURE IN LAKE KOMUKE

  丸山桃茄, 中山恵介, 駒井克昭, HO Getsunei, 坂口仁一, 田多一史, 佐藤之信

  2024, 土木学会論文集(Web), 80(17) (17)


• 阿寒湖のマリモ群生地と流域の水質特性およびマリモ内部水の経年変化

  寺田惇哉, 駒井克昭, 尾山洋一, 中山恵介

  2023, 水文・水資源学会研究発表会要旨集(Web), 2023


• Field Survey to Understand Daily Changes in CO2 Dynamics in Seawater at Eelgrass Field

  比屋根崇史, XIONG Bing, 小森博仁, 矢野真一郎, 中山恵介, 駒井克昭

  2022, 土木学会全国大会年次学術講演会(Web), 77th


• Comparison of non-point source load characteristics by runoff analysis in branches of the Kushiro River

  灘宏太, 駒井克昭, 中山恵介, 中下慎也

  2022, 土木学会北海道支部論文報告集(CD-ROM), (78) (78)


• Characterization of rare earth elements in terrestrial water and biological samples in the east Hokkaido

  篠原健人, 片岡俊徳, 駒井克昭, 尾山洋一, 中山恵介, 山田俊郎

  2021, 土木学会北海道支部論文報告集(CD-ROM), (77) (77)


• Source-region identification by adjoint frequency response analysis: an application to low-mode internal tides on the Australian North West Shelf

  Kenji Shimizu, Keisuke Nakayama

  Feb. 2020, Ocean Science Meeting 2020


• DEVELOPMENT OF SUBMERGED AQUATIC VEGETATION MODEL CONSIDERING BRANCH

  佐々木大輔, 中山恵介, 新谷哲也, 田多一史, 松本大輝, 駒井克昭

  2020, 土木学会論文集 B2(海岸工学)(Web), 76(2) (2)


• ENERGY ATTENUATION MODELLING UNDER THE BREAKING OF INTERNAL SOLITARY WAVES AND REPRODUCTION OF THE STRATIFIED LAKES WITH HIGH ACCURACY

  WANG Yuan, 中山恵介, 伊藤航, 岩田遼, 新谷哲也, 速水祐一, 藤原建紀

  2020, 土木学会論文集 B1(水工学)(Web), 76(2) (2)


• シミュレーションを用いた千苅貯水池における出水時の水質変化予測

  小幡 一貴, 清水 武俊, 小田 琢也, 小林 弘樹, 山元 幸之助, 中山 恵介

  公益社団法人 日本水道協会, 2020, 全国会議（水道研究発表会）講演集, 2020, 174 - 175, Japanese


• Mobility and partitioning of heavy metals in the basin of Mellah River, Algeria

  Saadia BOURAGBA, Katsuaki KOMAI, Keisuke NAKAYAMA, Toshiyuki CHIBA

  Jan. 2020, Water and Environment Technology Conference 2019


• Occurrence of hypoxia in a reservoir

  K. Yamamoto, S. Sakaguchi, N. Hayashi, K. Nakayama, K. Kobayashi

  Jul. 2019, AOGS Meeting


• ESTIMATION OF DISSOLVED SUBSTANCES TRANSPORT IN KUSHIRO RIVER BASIN USING DISSOLVED ION PATTERN

  駒井克昭, 中山恵介, 広木駿介, 阪口詩乃

  2018, 土木学会論文集 B1(水工学)(Web), 74(4) (4)


• 外的要因が球状マリモ形成に与える影響評価のための固液混相流モデルの開発

  林典子, 中山恵介, 尾山洋一, 若菜勇, 山田俊郎, 駒井克昭

  2018, 土木学会関西支部年次学術講演会講演概要集(CD-ROM), 2018


• 阿寒湖におけるマリモ球状化に影響を与える風の将来予測

  佐野史弥, 中山恵介, 山田俊郎, 佐藤之信, 丸谷靖幸, 駒井克昭, 尾山洋一, 若菜勇

  2016, 土木学会年次学術講演会講演概要集(CD-ROM), 71st


• Influence of nutrient and fine sediment control to primary productivity by benthic attached algae in forest watershed

  Katsuaki Komai, Asami Nagao, Masanori Nunokawa, Nozomi Watanabe, Yasuyuki Maruya, Keisuke Nakayama

  2016, IWA World Water Congress and Exhibition 2016, English

  [Refereed]

  Introduction international proceedings


• Climate Change Impact Assessment on Nutrient Discharge Using Multi-Model and Multi-Scenario of GCMs in Shiretoko

  Y. Maruya, S. Watanabe, K. Nakayama, T. Tanaka, Y. Tachikawa

  The 7th International Conference on Water Resources and Environment Research, 2016, The 7th International Conference on Water Resources and Environment Research, English

  [Refereed]

  Introduction international proceedings


• Organic carbon transport during flood due to rainfall in a headwater catchment of Kushiro Wetland, JAPAN

  Hajime Kasama, Katsuaki Komai, Yasuyuki Maruya, Keisuke Nakayama

  2016, Libra de articulos del XXVII Congress Latinoamericano de Hydraulica, English

  [Refereed]

  Introduction international proceedings


• Numerical solutions and simulations of surface/internal solitary waves

  Kakinuma Taro, Yamashita Kei, Nakayama Keisuke

  Kyoto University, Apr. 2015, RIMS Kokyuroku, 1946, 87 - 94, Japanese


• 農林地由来の栄養物質と溶存有機物の流出特性解析

  笠間基, 布川雅典, 駒井克昭, 中下慎也, 長尾麻未, 中山恵介

  2015, 応用生態工学会研究発表会講演集, 19th


• 釧路川流域における湿原再生に向けた栄養塩輸送量の評価手法に関する研究

  駒井克昭, 中山恵介, 河合守, 新谷哲也, 中下慎也

  2015, 土木学会年次学術講演会講演概要集(CD-ROM), 70th


• Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis

  Nakayama, K., Maruya, Y., Matsumoto, K., Komata, M., Komai, K., Kuwae, T.

  Copernicus GmbH, 2015, Biogeosciences Discussions, 12(7) (7), 5535 - 5557, English


• 内部ケルビン波の砕波により誘起される水平循環

  小窪一毅, 中山恵介, 新谷哲也, 柿沼太郎, 大塚淳一, 渡部靖憲, 駒井克昭, 清水健司

  2014, 土木学会北海道支部論文報告集(CD-ROM), (70) (70)


• 東京湾の水質予測に与える干潟の影響

  木下直貴, 中山恵介, 新谷哲也

  2014, 土木学会北海道支部論文報告集(CD-ROM), (70) (70)


• 網走川で発生する塩水遡上に関する研究

  星純平, 中山恵介, 新谷哲也, 早川博, NGUYEN Hoang-Duc

  2014, 土木学会北海道支部論文報告集(CD-ROM), (70) (70)


• Identification of major suspended sediment sources using X-ray florescense analysis: the Oromushi river basin case of study

  Carlos BEITIA, Keisuke NAKAYAMA, Naofumi OHTSU, Misao YAMANE, Shintaro YAMASAKI, Saadia BOURAGBA, Yasuyuki MARUYA, Katsuaki KOMAI

  2014, Proceedings of annual conference, Japan Society of Civil Engineering, Hokkaido Branch, 71, B-44, English

  Summary national conference


• Identification of dominant suspended sediment sources in a river basin using X-ray florescence analysis

  Carlos BEITIA, Keisuke NAKAYAMA, Naofumi OHTSU, Misao YAMANE, Shintaro YAMASAKI, Yuto YOSHIE, Yasuyuki MARUYA, Katsuaki KOMAI

  The transportation of materials with different chemical and physical properties from the headwaters all over a river basin up to the downstream end is a natural and indispensable mechanism to keep sound riverine ecosystems. However, from the aspect of ecological system, abnormal high sediment concentrations could cause biological, chemical and physical alterations of the river properties and secondary consequences at socio-economic range, such as decreasing in fishery production, rise in water treatment processes costs and loss of reservoirs storage capacity. Therefore, we made an attempt to use chemical composition analysis performed by X-rays fluorescence analysis (XRF) as a tool to identify the main sources of sediments from to the downstream end of a river basin.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2014, Proceedings of annual conference, Japan Society of Civil Engineering, Hokkaido Branch, 70, B-24 - 100115, English

  Summary national conference


• Projection of Nutrient Discharge by Using Different Bias Correction Method for Precipitation in Shiretoko

  Y. Maruya, K. Nakayama, T. Nakaegawa, T. Inoue, M. Komata, K. Komai, Y. Tachikawa

  Asia Oceania Geosciences Society 2014, 2014, Asia Oceania Geosciences Society 2014, English

  [Refereed]

  Summary international conference


• Nutrient circulation in Shiretoko using isotope analysis

  Sano Shiro, Nakayama Keisuke, Matsumoto Kei, Carlos Beitia, Maruya Yasuyuki, Komai Katsuaki, Inoue Tetsunori, Kuwae Tomohiro

  In a river, in which salmon and trout migrate upstream for spawning, Marine Derived Nutrient (MDN) plays great role in river ecosystem, and MDN is revealed to be necessary for sustainable ecological system. Nutrient is shown to be supplied from an entire river basin not just from an inside of a river. It is demonstrated that the consumption and restoration of migration fish by mammals and birds from a viewpoint of river ecosystem, which may result in the dispersion of MDN into an entire river basin by mammals and birds. Therefore, this study aims to reveal how MDN is restored into a river basin and how much the restoration rate of MDN is from the ocean into an entire watershed.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2014, Proceeding of Annual Conference, 27, p.100135 - 100135, Japanese

  Summary national conference


• Estimation method of production of methane in a lake

  Maruya Yasuyuki, Takeuchi Tomohiko, Nakayama Keisuke, Sasaki Masafumi, Komai Katsuaki

  The 5th IPCC report demonstrated that temperature rise is from 0.3 to 4.8 degrees. Methane is considered one of the most influential gasses on climate change, and the previous studies demonstrated that about one-fourth of methane emission is given from lakes and wetlands. However, the mechanisms of the occurrence of methane is not clarified enough. Therefore, this study aims to develop the estimation method of production of methane from benthic sediment in a lake. As a result, it is revealed that production of methane is negatively associated with DO concentration.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2014, Proceeding of Annual Conference, 27, p.100094 - 100094, Japanese

  Summary national conference


• 地球規模での環境変動が知床の栄養流出に及ぼす影響評価

  丸谷靖幸, 中山恵介, 仲江川敏之, 井上徹教, 小俣雅嗣, 石田哲也, 駒井克昭

  2014, 土木学会北海道支部論文報告集, 70, B-46, Japanese

  Summary national conference


• ラウス川流域におけるリン流出量と還元量の推定

  徳重彰倫, 中山恵介, 丸谷靖幸, 桑江朝比呂, 井上徹教, 松本経, 駒井克昭

  2014, 土木学会北海道支部論文報告集, 70, B-25, Japanese

  Summary national conference


• 宮古湾における底泥およびアマモのモニタリング結果(2012年10月)

  岡田知也, 丸谷靖幸, 中山恵介, 古川恵太

  Sep. 2013, 国土技術政策総合研究所資料, (752) (752), 16P, Japanese


• Field observation for clarification of mechanisms of methane emission in Freezing Lake

  Kokubo Kazuki, Maruya Yasuyuki, Nakayama Keisuke, Komai Katsuaki, Sasaki Masafumi

  The 4th IPCC report demonstrated that sea level rise is from 0.18 to 0.59 m and the increase in temperature is from 1.1 to 6.4 degrees. Methane is considered one of the most influential gasses on climate change, and the previous studies demonstrated that about one-fourth of methane emission is given from lakes and wetlands. However, the mechanism of the occurrence of methane with the effect of the freezing is not clarified enough. Therefore, this study aims to clarify water quality of freezing lake by using field observation. As a result, it is speculated that is accumulated large amounts of methane in lower layer in freezing season by forming stratification.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2013, Proceeding of Annual Conference, 26, 180 - 181, Japanese

  Summary national conference


• 内部ケルビン波の砕波により発生する流れに関する研究

  小窪一毅, 中山恵介, 新谷哲也, 大塚淳一, 岡田知也, 渡部靖憲, 丸谷靖幸

  01 Aug. 2012, 土木学会年次学術講演会講演概要集(CD-ROM), 67th, ROMBUNNO.II-055, Japanese


• Numerical calculation of tsunami generation and propagation considering velocity distribution or density stratification (New Developments in Study of Nonlinear Wave Phenomena)

  Kakinuma Taro, Yamashita Kei, Nakayama Keisuke

  Kyoto University, Jul. 2012, RIMS Kokyuroku, 1800, 1 - 13, Japanese


• 環境流体解析のための簡易Wetting and Dryingスキーム

  新谷哲也, 中山恵介, 中本篤嗣

  2012, 水工学論文集(CD-ROM), 56


• Partial Cellを導入した塩水遡上解析

  中本篤嗣, 中山恵介, 新谷哲也

  2012, 土木学会北海道支部論文報告集(CD-ROM), (68) (68)


• Sediment transportation area-weighted rate evaluation by chemical composition analysis in a river basin, using Oromushi River as case of study

  Carlos BEITIA, Keisuke NAKAYAMA, Tetsuya ISHIDA, Yasuyuki MARUYA, Katsuaki KOMAI

  Sediment transportation rate from 18 domains within the Oromushi River basin was studied by taking in account the main land uses i.e. agricultural fields and forests and each domain area. Chemical composition analysis was conducted to determine each domain contribution to the sediment transportation rate in the whole river. The correlation between the downstream end and each domain was calculated as a function of the similarity between the concentrations of the most important components determined by principal component analysis statistical method. A method which enables an estimation of the sediment transportation rate from each domain of the basin was developed based on field measurements of 6 years rainfall and sediment concentration data sets.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2012, Proceedings of 26th annual conference, Japan Society of Hydrology and Water Resources, 26, 164 - 165, English

  Summary national conference


• Comparison of Water Circulation Mechanisms between the 1970s and the 2000s in Kushiro Wetland

  Y. Sugawara, Y. Maruya, K. Komai, K. Nakayama, J. Kato

  11th International Conference on Civil and Environmental Engineering, 2012, Proceedings of the 11th International Conference on Civil and Environmental Engineering, 89 - 90, English

  [Refereed]

  Introduction international proceedings


• Projection of strong wind by using MRI-AGCM3.1 and CMIP3 Multi-Models in Tokyo Bay

  Maruya Yasuyuki, Nakayama Keisuke, Nakaegawa Toshiyuki, Komai Katsuaki, Okada Tomonari

  Meteorological conditions are revealed to change, which may have caused more flood disaster, greater typhoon and so on in terms of climate change. Therefore, strong wind pattern is also expected to change and to have an effect on water quality in Tokyo Bay.  This study aims to clarify the impact of meteorological change on the occurrence of strong south-west winds (KEw), which enhance rapid recovery from hypoxia by using MRI-AGCM3.1S, MRI-AGCM3.1H, MRI-AGCM3.1L, and eight models in CMIP3 outputs. As a result, it is suggested that recovery from hypoxia in the future does not occur more rapidly than the present.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2012, Proceeding of Annual Conference, 25, 82 - 83, Japanese

  Summary national conference


• 釧路湿原における分布型流出モデルの再現性の検討

  大塚泰之, 丸谷靖幸, 中山恵介, 菅原庸平

  2012, 土木学会北海道支部論文報告集, 68, B-20, Japanese

  Summary national conference


• 知床における海陸の栄養塩循環量の推定

  アイヌルアブリズ, 中山恵介, 丸谷靖幸, 井上徹教, 桑江朝比呂, 舘山一孝, 岡田知也, 加藤淳子, 石田哲也

  2012, 土木学会北海道支部論文報告集, 68, B-59, Japanese

  Summary national conference


• 東京湾の生態系モデル開発に向けたパーシャルセルの適用

  木下直貴, 中山恵介, 新谷哲也, 丸谷靖幸

  2012, 土木学会北海道支部論文報告集, 68(68) (68), B-59, Japanese

  Summary national conference


• 海面上昇を考慮した釧路湿原への塩水遡上の影響評価

  中本篤嗣, 新谷哲也, 中山恵介, 丸谷靖幸, 石田哲也, 法村賢一

  2011, 水工学論文集(CD-ROM), 55


• 東京湾におけるオブジェクト指向型環境流体モデルの適用

  片山幸明, 中山恵介, 新谷哲也

  2011, 土木学会北海道支部論文報告集(CD-ROM), (67) (67)


• 異なる成層場における内部ケルビン波の斜面上での砕波

  小窪 一毅, 中山 恵介, 新谷 哲也, 丸谷 靖幸, 岡田 知也, 渡部 靖憲, Kokubo Kazuki, Nakayama Keisuke, Shintani Tetsuya, Maruya Yasuyuki, Okada Tomonari, Watanabe Yasunori

  公益社団法人土木学会北海道支部, 2011, 論文報告集, 23(68) (68), Japanese


• Rainfall Analysis in Subtropical Panama

  Junko KATO, Erick VALLESTER, Reinhardt PINZON, Jose FABREGA, Jorge ESPINOSA, Keisuke NAKAYAMA, Toshiyuki NAKAEGAWA, Yasuyuki MARUYA, Katsuaki KOMAI

  2011, Proceedings in the symposium on Extreme Weather and Impact Assessments - for contributing the IPCC AR5 -, 39, English

  Summary national conference


• Projections of Rainfall Intensity in Central America, Panama

  Carlos BEITIA, Yasuyuki MARUYA, Erick VALLESTER, Reinhardt PINZON, Jose FABREGA, Berta OLMEDO, Keisuke NAKAYAMA, Toshiyuki NAKAEGAWA, Katsuaki KOMAI

  2011, Proceedings in the symposium on Extreme Weather and Impact Assessments - for contributing the IPCC AR5 -, 40, English

  Summary national conference


• GCMを用いた東京湾におけるDO濃度回復に関する将来予測

  丸谷靖幸, アイヌルアブリズ, 中山恵介, 仲江川敏之, 古川恵太

  2011, 土木学会年次学術講演会報告集, 66, II-195, Japanese

  Summary national conference


• GCMを利用した東京湾における強風の将来予測

  丸谷靖幸, 中山恵介, 仲江川敏之, アイヌルアブリズ, 駒井克昭

  2011, 極端気象現象とその気候変動による影響評価に関するシンポジウム（Ⅱ）要旨集, 41, Japanese

  Summary national conference


• 知床ラウス川からの栄養塩フラックスの推定

  アイヌルアブリズ, 加藤淳子, 丸谷靖幸, 井上徹教, 桑江朝比呂, 中山恵介

  2011, 第24回（2011年度）水文・水資源学会総会・研究発表会要旨集, P.96, Japanese

  Summary national conference


• 知床ラウス川流域における安定同位体比を用いた海起源栄養塩の分布解析

  アイヌルアブリズ, 中山恵介, 丸谷靖幸, 桑江朝比呂, 石田哲也

  2011, 土木学会北海道支部論文報告集, 67, B-22, Japanese

  Summary national conference


• GCM を用いた東京湾に対する風速の再現性の基礎的検討

  丸谷靖幸, 中山恵介, 仲江川敏之

  2011, 土木学会北海道支部論文報告集, 67, B-45, Japanese

  Summary national conference


• 潜堤上における非線形内部波の伝播特性 (非線形波動現象の数理と応用)

  柿沼 太郎, 山下 啓, 中山 恵介

  京都大学, Aug. 2010, 数理解析研究所講究録, 1701, 206 - 211, Japanese


• 網走川において風波が塩水浸入に及ぼす影響評価

  佐久間慎雄, 中山恵介, 柿沼太郎, 新谷哲也

  2010, 土木学会北海道支部論文報告集(CD-ROM), (66) (66)


• コリオリを考慮した斜面上での内部波の砕波について

  福岡将太, 中山恵介, 新谷哲也, 角谷和成

  2010, 土木学会北海道支部論文報告集(CD-ROM), (66) (66)


• Nutrient cycle evaluated by isotope in Shiretoko

  Maruya Yasuyuki, Nakayama Keisuke, Kuwae Tomohiro, Ayinuer Abulizi

  知床半島では食物連鎖が顕著にみられ，流氷に含まれる多くのプランクトンや栄養が海域起源の栄養を陸域に供給する重要な役割を果たしている．このプランクトンを食べた栄養豊富なサケなどが遡上することで陸域へと海域起源の栄養が運ばれ，その栄養が陸域に住む生物の糧となり，いずれは流出といった形で海域へと戻り循環されている．そのため，このような知床の特殊な生態系システム保全を行うための対策を提案する必要がある．そこで本研究では，ラウス川流域における水循環・栄養塩循環機構の解明，環境の維持管理を行うための政策提案を目的とし，採泥を行い安定同位体比の解析を行った．その結果，知床ではサケの遡上という形で海域起源の栄養が運ばれ，クマやキツネに捕食されることにより，海域起源の栄養が陸域に広がっているのではないか，また，季節によって栄養塩の流出量にも変化が起こるのではないかと推測された.

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2010, Proceeding of Annual Conference, 23, P.141 - 141, Japanese

  Summary national conference


• 安定同位体比を用いた知床における栄養塩循環の基礎的検討

  小野智也, 中山恵介, 桑江朝比呂, 丸谷靖幸, アイヌルアブリズ

  2010, 土木学会北海道支部論文報告集, 66, B-38, Japanese

  Summary national conference


• 2007年～2008年における網走湖の観測結果について

  丸谷靖幸, 中山恵介, 堀松大志, 大田見定

  2009, 土木学会北海道支部論文報告集, 65, B-28, Japanese

  Summary national conference


• 2006年10月の洪水時における網走湖内の流動解析

  中山恵介, 堀松大志, 丸谷靖幸, 徐乃丹, 米元光明

  2009, 土木学会北海道支部論文報告集, 65, B-39, Japanese

  Summary national conference


• Environmental evaluation of wind effect and internal Kelvin waves on mass

  Nakayama Keisuke, Horimatsu daishi, Sumiya Kazunari, Maruya Yasuyuki, Hayakawa Hiroshi

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2008, Proceeding of Annual Conference, 21, P.85 - 85, Japanese

  Summary national conference


• DO concentration near the seabed in Tokyo Bay - response to rainfall -

  Nakayama Keisuke, Okada Tomonari, Furukawa Keita

  夏季における東京湾の湾央から湾奥にかけて，底層での有機物の分解に伴う酸素消費によって，底層に貧酸素水塊が発生することが良く知られており，この貧酸素水塊は，東京湾における生態系，水質環境に大きな影響を及ぼしていることから，どのようなメカニズムで底層の溶存酸素（DO）濃度が変化しているかを把握することは重要である．通常，夏季におけるエスチュアリー循環での湾内水の湾外水との交換は20日から30日であり，河川出水が生じると交換がより促進されることが知られている．そのため，河川出水が生じるとDO濃度が大きく回復する可能性がある．そこで本研究では，まず湾央の底層におけるDO濃度に着目し，河川出水イベントによる影響評価手法確率のためのDO濃度再現モデルの作成を行うことを目的とした．その結果，観測地点におけるDO濃度は，河川流入によるエスチュアリー循環の変化によって大きく変動していることが確認された．

  THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2006, Proceeding of Annual Conference, 19(0) (0), 65 - 65


• 荒川河口域における混合形態に伴うChlorophyll-α動態と海域への河川流入負荷量変動

  岡田 知也, 中山 恵介

  国土技術政策総合研究所, Jun. 2003, 国土技術政策総合研究所資料, (87) (87), 1 - 23,巻頭1〜3, Japanese


• 環境施策に資する内湾域の総合的な環境把握を目指したMEL1D-MBモデルの構築

  古川 恵太, 中山 恵介, 岡田 知也

  国土技術政策総合研究所, Dec. 2001, 国土技術政策総合研究所研究報告, (1) (1), 1 - 3,1〜16, Japanese


• Structures of Snow Clouds Associated with a Cold Air Flow

  Keisuke Nakayama, Kazuyoshi Hasegawa, Mutsuhiro Fuzita

  1998, Journal of Hydraulic, Coastal and Environmental Engineering, (593) (593), 1 - 10

• 湿地の科学と暮らし－北のウェットランド大全

  NAKAYAMA KEISUKE

  Others, 北海道大学出版会, Apr. 2017, Japanese

  Scholarly book


• 地形の辞典

  日本地形学連合編, 鈴木隆介編, 砂村継夫編, 松倉公憲編, NAKAYAMA KEISUKE

  Others, 朝倉書店, Feb. 2017, Japanese

  Scholarly book


• 図説日本の海岸

  柴山知也, 茅根創編, NAKAYAMA KEISUKE

  Others, 朝倉書店, Apr. 2013, Japanese

  Scholarly book


• The Environment in Asia Pacific Harbors

  E. Wolanski, NAKAYAMA KEISUKE

  Others, Springer, Apr. 2006, English

  Scholarly book

• Maximization of blue carbon sequestration in estuaries and freshwater lakes

  中山 恵介, 矢野 真一郎, 駒井 克昭, 新谷 哲也, 宇野 宏司

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, 01 Apr. 2022 - 31 Mar. 2026


• 表面波・内部波の非線形性及び分散性に対する地形の影響に関する数値解析的研究

  中山恵介, 辻英一

  九州大学応用力学研究所, 九州大学応用力学研究所共同利用研究, 鹿児島大学, Apr. 2024 - Mar. 2025


• Development of environmental dynamic analysis model for advanced management of environmental load connecting forest-village-river-sea

  駒井 克昭, 中山 恵介, 中下 慎也

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kitami Institute of Technology, 01 Apr. 2021 - 31 Mar. 2024

  森里川海にわたる流域～沿岸生態系の保全は豊かな自然と持続可能な循環型社会の構築に寄与するものと考えられる．近年では，海域への過剰な流入負荷対策は進み，N，Pの環境基準の達成率は改善されたが，海底に蓄積された大量に栄養塩を含む有機泥は貧酸素水塊や栄養塩の溶出の原因となり，海域の生態系や物質循環過程は劣化していることから，きれいで豊かな海を取り戻すには順応的な流域の栄養塩管理も必要である．沿岸域の背後地である流域からの負荷の発生源は，家庭や工場，事業所等の特定汚染源と市街地の舗装面や田畑，森林，湿地等の非特定汚染源に分類される．例えば，都市や畑地，牧草地などに利用されている地域や森林，湿地，湖沼などの自然地域がモザイク状に分布する場合，面源負荷は自然的・社会的な要因により大きく変化しうる．集中豪雨による都市域からの表面流出，過疎化や高齢化による里地・里山の荒廃，農業の大規模化や耕作放棄，気候変動に伴う湿地の植生変化や湖沼の富栄養化等は，面源負荷の質と量に大きく影響を及ぼすと考えられることから，流域の面源負荷対策を評価・予測できる拡張性の高い環境動態解析モデルの構築は喫緊の課題である．本研究では，自然・人為由来の様々な物質の起源を表すマーカー情報（MDF）を開発し，森里川海をつなぎ海洋生態系の栄養物質になりうる物質の由来を追跡する環境動態解析手法を構築することである．今年度においては，流域固有のMDFを定量するための分析メソッドの構築とその有用性が確認され，物質の起源を表す基礎的知見が得られた．また，環境動態解析モデルへのMDFの組み込みに向けモデルの拡張，面源負荷発生サブモデルの適用性，および粒子挙動のモデルパラメータの検証がなされ，環境動態解析手法の構築に向けて基礎的かつ重要な成果が得られた．


• Development of 3D temperature monitoring and predicting system in reservoirs using UAV

  新谷 哲也, 赤松 良久, 宮本 仁志, 中山 恵介

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Tokyo Metropolitan University, 01 Apr. 2020 - 31 Mar. 2023

  本研究は湖沼・貯水池の水温分布の空間的な把握を目的に進められている．今年度は．東京都が管轄する小河内貯水池において赤外線搭載ドローンと小型水温計を用いた現地観測を行った．貯水池では，視界の開けたダム堤体前と上流側の河川流入部を調査対象区域とした．沿岸域や湖の水面で行われるドローン撮影では，撮影された個々の画像内に画像連結に利用される特徴点の少ないことが問題点として挙げらる．そこで，今年度は，ドローンの進行方向や緯度経度情報から撮影範囲を特定し，画像を合成するアルゴリズムの開発を行った．その結果，特徴点マッチング法では困難であった水面上の画像合成が一定の精度で可能となった．ドローン画像から推定した水面水温と貯水池の水面に設置した水温計の測定結果を比較したところ良好な一致を示し，ドローンによる温度推定が可能であることが明らかとなった．また，上流部における観測では，植物プランクトンの高濃度で分布すると思われる水面付近では，空間的な温度変化が観測されるなど，可視光だけではなく温度分布からの水質把握の可能性も明らかとなった． 一方，ドローンと同様に間接的な空間的な水温変化の把握方法である衛星画像による温度推定も同時に行った．衛星データにはLandsat8の画像を用いた．衛星画像は2週間に一度程度の撮影間隔であるが，水域全体の水温分布を把握することができる．衛星画像から推定した温度は，東京都で定期的に収集された観測データと合理的な一致を確認することができた．衛星画像から推定された温度分布から，季節的な水温変化，流入河川の影響，上流から下流に向かって変化する水温などを定量的に確認することができた．


• Improvement of environmental dynamics analysis of river basin using specific substance information in cold region

  Komai Katsuaki

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kitami Institute of Technology, 01 Apr. 2015 - 31 Mar. 2018

  Background to the water environment problems in the Hokkaido region includes snow falling and melting unique to cold regions, ice formation / deicing of rivers and lakes, which complicates material dynamics, as well as a hinterland with the source of various contamination from human activities.These background is deeply involved in the barriers to the scientific elucidation of material dynamics and the solution of technical problems. In this study, we developed a material cycle analysis method using dissolved ions, rare earth elements, fluorescent dissolved organic substances, etc, which are information on intrinsic material origin of natural origin and anthropogenic origin in a typical watershed of cold snow. In addition, using these material origin information, we clarified that hydrological and hydraulic phenomena at snow melting / snow covering season supports the basic habitat environment such as aquatic organisms.


• Exploring of salmon spawning sites and abundance using Steller's sea eagle tracking in Hokkaido

  Matsumoto Kei, NAKAYAMA Keisuke

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Challenging Exploratory Research, Kitami Institute of Technology, 01 Apr. 2014 - 31 Mar. 2016

  In winter, although Steller’s sea eagles can be seen at salmon spawning sites in Hokkaido, little is known for their potential as a field indicator which allows us to estimate the salmon abundance. In this study, we examined temporal and spatial distribution of eagles along the salmon spawning river in eastern Hokkaido. More eagles occurred in the riparian forests in relation to salmon abundance. The spatial patterns of eagles were matched the results from radar observations beside the spawning sites. We also tested how the salmon runs and eagle’s consumption affected on marine derived nutrient inputs into the terrestrial ecosystem based on the use of stable isotope signature (δ15N, δ13C) of terrestrial plants. Stable isotope ratios of plants from spawning sites were higher than those from non-spawning sites. Thus, eagle occurrences and stable isotope signature can be the index of salmon abundance in the spawning rivers.


• 河口域における水循環と塩水遡上を予測する包括的フレームワークの開発

  中山 恵介, NGUYEN Duc

  日本学術振興会, 科学研究費助成事業, 特別研究員奨励費, 北見工業大学, 01 Apr. 2013 - 31 Mar. 2015

  ベトナムのように海岸線から低平地が広がる地域では，網状の河道網が形成されることが多く，その水源を利用して米作などの農業が進む傾向にある．一方で，海に面し低平地であることから，潮位の変化に敏感に反応した塩水の遡上が存在し，その海水を利用したエビの養殖も盛んとなることが多い．米作には塩水の進入は抑制しなくてはならない問題であり，農業および水産業の両者を良好な状態に保つためには，どの程度の淡水が網状河川内を流れており，どれくらいの距離だけ塩水が進入するかを理解する必要がある．また，河道内の塩水遡上の変化は，農業・水産業的な問題だけではなく，周辺の植生をはじめとした生物環境を大きく変化させるため，適切な現象の評価が望まれている．そこで本研究では，河川河口域で生じる塩水遡上現象を簡易的に診断するフレームワークの構築を目的としている． 容易に利用できるようにするため，工夫されたベルヌイに基づいた塩水遡上モデルを利用し，網走川，太田川，およびベトナムのRed Riverを対象とした解析を実施した．網走川においては，河川水位や潮位データを利用した塩水遡上距離に関するモデルの適用性の検討を行い，その再現性の高さを示すことができた．Red Riverにおいても同様な検討を行い，網走川同様に高い再現性を確認することができた．一方で，網状河川における淡水流量の推定に関しては，広島を流れる太田川のデルタおよびMekong Riverを対象とした再現計算を実施，よい再現性を得ることができた． 以上の成果により，新たな塩水遡上管理手法（フレームワーク）を提案することを出来たと考える．このフレームワークは，日本のみならず，発展が遅れている後進国においても容易に利用できるツールであると言える．


• Sedimentation process on organic settling matter in brackish lake in cold region

  KOMAI Katsuaki, NAKAYAMA Keisuke, NAKASHITA Shinya, YOKOYAMA Hiroshi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kitami Institute of Technology, 01 Apr. 2012 - 31 Mar. 2015

  Measuring of particle size distribution and modeling of particle settling were conducted, and new analytical method on settling velocity distribution from temporal variation of particle size distribution was proposed. From the results of settling experiment by using clay mineral and dispersing agent, the reliable data were obtained. Settling velocity of lake sediment estimated from the model by using ignition loss and carbon/nitrogen ratio was slightly larger in the east of Hokkaido than in the temperate region. The differences of organic matter and solvent influences settling properties of organic settling matter. In Lake Komuke, the settling velocity distribution of organic settling matters also prominently differs. Settling velocity and flocculation were closely related to organic substance depending on seawater exchange rate in the brackish lake.


• Methane emission in the Arctic Circle by considering dissolved oxygen concentration

  NAKAYAMA Keisuke

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kitami Institute of Technology, 2011 - 2013

  The greenhouse effect of methane is 25 times as much as carbon dioxide although the decomposition speed of carbon dioxide is slower than methane. Methane is found to occur in the Arctic Circle mainly, in which there are possibilities that permafrost melts more in the future due to the climate change. The occurrence of new ponds induced by the melting permafrost is expected to increase the release of methane. This study thus aims to evaluate the release rate of methane from eutrophicated ponds or lakes by modeling the occurrence of methane from the polluted sediment on the bottom. We attempted to investigate the release rate of methane by taking into account water temperature, sulphate ion concentration, and dissolved oxygen concentration. As a result, dissolved oxygen concentration is found to be the most influential and significant factor which controls the release rate of methane from polluted sediment.


• Studies on glaciological environment and disaster prevention for Shiretoko Peninsula area.

  TAKAHASHI Shuhei, SASAKI Masafumi, OOHASHI Tetuya, KAWAMURA Akira, ENOMOTO Hiroyuki, SUZUKI Souichiro, TAKAHASHI Kiyoshi, KAMEDA Takao, SUGAWARA Noriyoshi, HORI Akira, TATEYAMA Kazutaka

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), Kitami Institute of Technology, 2007 - 2010

  Sea ice stays long around Shiretoko peninsula due to the "Dam Effect" against to the sea ice flow. Snow accumulation varies much in mountainous area, which depends on topography. The unique nutrient circulation among sea, river, fish and inland animals was confirmed by stable isotope analysis. The diaster of short circuit by salty snow in snow storm was observed and exprimented.


• Study on re-suspension, transport, and settlement processes of particulate matter in an estuarine environment under multi-scale effects

  FURUKAWA Keita, NAKAYAMA Keisuke

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), National Institute for Land and Infrastructure Management, 2007 - 2009

  This study aims to clarify the mechanisms of mass transport in a network of canal around Tokyo Bay by taking into account multi-scale effect on flow field, which is considered one of the most complicated network systems in Japan. In the analysis, three-dimensional numerical computation and vertically integrated two-dimensional numerical computation models were applied in order to reveal energy transfer and mass transport in a stratified flow field. In the field observation, salinity and dissolved oxygen were measured with the interval of 10min for a few months at several stations, such as Higashi-Ogijima, Chiba-Tohyo and Tokyo Port, which reveals that water quality in Chiba-Tohyo influences in Tokyo Port and Higashi-Ogijima. On the other hand, field observation regarding dissolved oxygen demonstrated that anoxia in canal does not have any relation with that in the bay head because of the discontinuity of stratification effect. Therefore, it is found to be necessary to evaluate the structure of stratification in order to clarify the influential region when you analyze mass transport in multi-scale stratified flow field.


• Mechanisms of horizontal circulation induced by breaking of internal Kelvin waves over a slope

  NAKAYAMA Keisuke

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), Kitami Institute of Technology, 2007 - 2009

  In general, stratification appears in an enclosed bay, such as Tokyo Bay, due to fresh water input from rivers and solar radiation during summer. When external force is given in a stratified flow field, larger amplitude internal waves are induced compared to water surface waves. The internal waves are likely to be deformed and to become internal Kelvin waves due to the Coriolis effect, which break over a slope in a shallow water region. However, the influence of internal Kelvin waves has not been revealed in the previous studies. Therefore, this study aims to clarify the influence of internal Kelvin waves on a stratified flow field by using laboratory experiments and numerical analysis. As a result, flow toward the breaking zone is induced by the breaking of internal Kelvin waves, which does not occur without the Coriolis effect. The flow toward the breaking zone is also found to drive cyclonic horizontal circulation.


• Integration of Distributed Hydrological Model which includes the model of POM and Ecological Model in Tokyo Bay

  NAKAYAMA Keisuke

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), National Institute for Land and Infrastructure Management, 2005 - 2006

  Firstly, the grid size effect was investigated using Distributed Hydrological Model. In general, grid-based distributed hydrological models are considered to be a very effective flood modeling tool for basin-wide flood risk analysis due to their capabilities of simulating river and surface inundations at high spatio-temporal resolutions by taking advantages of grid-based data from meteorological models, radar and satellite remote sensing. Selecting an appropriate grid size is critically important for any application of a grid-based model, which requires proper understanding of effects of grid sizes on simulated outcomes. The paper presents the outcomes of a study conducted to analyze the effects of grid resolution in simulated river peak flows and surface inundation in two selected river basins using a process-based distributed hydrological model. The effect of integration of river model and estuary model was evaluated to demonstrate the benefit of an integrated estuary model. An integrated estuary model consists of hydrological model, estuary model and meteorological model. In general, salinity distribution may be found to be significant for the evaluation of long time scale water quality in an enclosed bay because salinity mainly controls density in a bay. Therefore, the influence of tide on salinity in a bay was investigated to demonstrate the necessity of an integrated estuary model. Two different river discharges and three different tidal amplitudes were used to examine the influence of tidal effect on salinity flux at the mouth of river. It was revealed that, for the case where river discharge at the upstream end of river model is constant and river discharge due to tide is included, with increasing reduction of average salinity from initial conditions, the river discharge at the upstream end was smaller than river discharge due to tide. The integration of river model, which can include the feature of estuary, and estuary model is, thus, found to be important to evaluate salinity flux at the mouth of river accurately.


• Development of integrated Tokyo Bay model combined with Distributed Hydrological Model (DHM)

  NAKAYAMA Keisuke, DUTTA Dushmanta

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), National Institute for Land and Infrastructure Management, 2003 - 2004

  Two minor projects are included in this project. (1) Development of a highly improved flow model based on LES model. (2) Application of a distributed hydrological model into Tsurumi River. Each project has achieved the following results. (1) Non-hydrostatic three-dimensional LES model A non-hydrostatic three-dimensional LES model (MEL3D) was developed in this project. The main features of this model are the CIP method, the ALE method, the SOR method, and Second-Order Closure Scheme (SOC). The validation was done by making a comparison with laboratory experiment results in terms of internal wave motion in a rectangular open channel tank. The results from laboratory experiment were agreed very well with numerical simulation results, such as flow field obtained using laser Doppler current meter. The verified MEL3D was applied to reproduce flow field in Tokyo Bay. The boundary condition on the sea-surface was given by using interpolated wind field obtained from AMeDAS. Real-time simulator was also developed by using html, which can enable us to access to see the real-time flow field through web page. The temporal web page address is http://210.251.65.4/unity/. Because this address will not be available in the near future, please access to the web page, http://www.nilim.go.jp/, and find the page to see the real-time simulation result. This model will be improved in the next project in order to include the reproduction of the distribution of dissolved oxygen demand, which may cause 'Aoshio' around the head of Tokyo Bay. (2) Distributed hydrological model GIS data set in Tsurumi River Basin was collected to use as an input for a distributed hydrological model(DHM). Although DHM is a physically based hydrological model and does not include meaningless coefficients, some coefficients had to be evaluated by calibration because of the difficulty obtaining all the spatially distributed coefficients in Tsurumi River Basin. The calibration was successfully done, and the results were compared with those from a tank model. Unfortunately, it was found from the comparison that DHM has to be improved more to obtain better results.


• 札幌周辺に豪雪をもたらす収束雪雲発生・推移予測に関する野外計測・数理解析的研究

  中山 恵介

  日本学術振興会, 科学研究費助成事業, 奨励研究(A), 北海道大学, 1996 - 1996

  北海道において特有な現象である,冷気流をともなった雪雲による降雪現象の解明のため,カイト気球による観測を昨年まで2年連続で行ってきた.冷気流は,放射冷却現象により発生した冷気塊が周りの空気より密度が大きくなることにより,二層流のごとく山地斜面に沿って,川の流れのように流下する現象である.そのため,その構造は鉛直方向に地表面から300m程度までの間において温度・湿度に大きな変化(温度であれば地表面から100m程度まで上空温度より5℃程度低くなる)をもつ. 昨年までのカイト気球観測において,2ケースほどの冷気流をともなった雪雲を観測することが出来た.その時の上空季節風風速は西風に近いものであった.本年度も,昨年までとどうように1ケースの冷気流をともなった雪雲を観測することが出来たが,上空季節風風速が北風であった.これまで数値計算により,季節風風速・風向が冷気流張り出しおよび雪雲形成形状に大きな影響を与えることが分かっており,昨年までと異なったカイト気球観測を行うことが出来たことは,非常に有用なデータを与えると考える.更に,今年度からは『衛生ひまわり』のデータを入手することが出来ており,レーダデータだけで判断していた冷気流をともなう雪雲が,より広範囲な視点から確認された. 先に述べたが,数値計算も平行して行い,昨年までの冷気流をともなった雪雲の再現計算を行い,良好な結果を得た.更に,数値計算は仮想の条件での冷気流の推移も計算できることから,数ケースの計算を行うことにより,冷気流のさまざまな条件の違いによる張り出し結果の変化についても知ることが出来た. 今後は,より多くの観測・数値計算による再現を行い,予測可能であることを示し,雪害対策へと役立てたい.