Researcher Database

Toshiki Iwasaki
Faculty of Engineering Civil Engineering Natural Disasters and Adaptation
Associate Professor

Researcher Profile and Settings

Affiliation

  • Faculty of Engineering Civil Engineering Natural Disasters and Adaptation

Job Title

  • Associate Professor

J-Global ID

Research Interests

  • numerical simulation   morphodynamics   river engineering   hydraulic engineering   

Research Areas

  • Social infrastructure (civil Engineering, architecture, disaster prevention) / Hydroengineering

Academic & Professional Experience

  • 2019/06 - Today Hokkaido university Graduate school of engineering Associate professor
  • 2016/06 - 2019/05 Civil engineering research institute for cold regions River engineering Researcher
  • 2014/05 - 2016/05 University of Illinois Urbana-Champaign Department of civil and environmental engineering Research scholar
  • 2013/04 - 2014/05 Hokkaido university Graduate school of engineering Postdoctoral research fellow

Education

  • 2010/04 - 2013/03  Hokkaido university  Graduate school of engineering
  • 2008/04 - 2010/03  Hokkaido university  Graduate school of engineering
  • 2006/04 - 2008/03  Hokkaido university  School of engineering  civil engineering
  • 2001/04 - 2006/03  Tomakomai national college of technology  civil engineering

Association Memberships

  • American geophysical union   JAPAN SOCIETY OF CIVIL ENGINEERS   

Research Activities

Published Papers

  • Toshiki Iwasaki, Gary Parker
    Proceedings of the National Academy of Sciences of the United States of America 0027-8424 2020/01 [Refereed][Invited]
  • Shimizu Yasuyuki, Nelson Jonathan, Ferrel Kattia Arnez, Asahi Kazutake, Giri Sanjay, Inoue Takuya, Iwasaki Toshiki, Jang Chang-Lae, Kang Taeun, Kimura Ichiro, Kyuka Tomoko, Mishra Jagriti, Nabi Mohamed, Patsinghasanee Supapap, Yamaguchi Satomi
    EARTH SURFACE PROCESSES AND LANDFORMS 0197-9337 2019/07/17 [Refereed][Not invited]
  • Zhang Li, Iwasaki Toshiki, Li Tiejian, Fu Xudong, Wang Guangqian, Parker Gary
    SCIENTIFIC REPORTS 9 2045-2322 2019/04/16 [Refereed][Not invited]
  • 岩崎 理樹, 岡部 博一, 島田 友典, 矢部 浩規, 米元 光明
    寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report 土木研究所寒地土木研究所 (786) 11 - 20 2432-2652 2018/11 [Not refereed][Not invited]
  • Toshiki Iwasaki, Satomi Yamaguchi, Hiroki Yabe
    E3S Web of Conferences 40 2018/09/05 [Not refereed][Not invited]
     
    © The Authors, published by EDP Sciences, 2018. An understanding of bedload transport processes is an essential research goal for better prediction of river morphology and morphodynamics as well as the transport and fate of sediment-bound materials in river systems. Passive tracer particles have been used widely to monitor bedload transport processes in rivers by measuring the spatiotemporal distribution of the bedload tracers. Here, we propose a numerical model for reproducing the transport of bedload tracers in river systems, more specifically, the behaviours of bedload tracers under the influence of complex river morphodynamics. A two-dimensional morphodynamic model is combined with a flux-based bedload tracer model with use of the active layer approach. The model is applied to a laboratory experiment that demonstrates the transport processes within the channel of bedload tracers supplied from the floodplain. The numerical model effectively reproduces the main features of the experiment, namely, the bedload tracers supplied from the floodplain due to bank erosion deposit onto sand bars developed within the channel. Because the sand bars cause a very long residence time of the bedload tracers within the bed, the transport speed of the tracers is slowed significantly under the influence of bar formation and channel migration.
  • Jun Okuda, Yasuyuki Shimizu, Tomoko Kyuka, Toshiki Iwasaki, Yoshiaki Ishida
    Proceedings - International Association for Hydro-Environment Engineering and Research (IAHR)-Asia Pacific Division (APD) Congress: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018 2 1007 - 1014 2018/09/01 [Not refereed][Not invited]
     
    © Proceeding of the 21st LAHR-APD Congress 2018. All rights reserved. There was a record breaking rainfall by Typhoon Lionrock over eastern Hokkaido in August 2016. Two levee breaches were caused by this rainfall leading to inundation disaster at Ikutora region in Minami Furano town. According to a field survey, the inundation disaster started from an upstream point at first, then the flood flow went through a flood plain and reached a downstream levee, finally overtopping to a river channel caused the second breach at downstream point. Since the flood started during midnight, a detailed explanation of the flood's behavior and a procedure of breaches remain unclear. In this study, we have investigated the river channel deformation and the levee erosion using a 2-dimensional numerical analysis. The computed results showed good agreement with field survey data regarding the inundation area, breach points, and the river channel deformation. Especially, the starting time of the inundation in the numerical analysis agreed with expected time estimated by field survey reports. The computational results indicate that with the increase of discharge, the development of a point bar pushed the channel near the upstream of the breach point toward outer bend of the channel meander. This channel migration may cause severe levee erosion. In the same time, the water level went up and overtopping flow happened. It suggests that both the bank erosion caused by the channel migration and overtopping flow caused the large-scale levee breach. Regarding the downstream breach, the results showed that the breach was caused by an overtopping flow from the floodplain to the river channel. which was expected by the field survey.
  • 濱木 道大, 岩崎 理樹, 井上 卓也, 清水 康行
    水工学論文集 Annual journal of Hydraulic Engineering, JSCE 土木学会 63 I_955 - 960 1880-8751 2018 [Not refereed][Not invited]
  • 岩崎 理樹, 井上 卓也, 音田 慎一郎, 矢部 浩規
    水工学論文集 Annual journal of Hydraulic Engineering, JSCE 土木学会 63 I_643 - 648 1880-8751 2018 [Not refereed][Not invited]
  • IWASAKI Toshiki, INOUE Takuya, YABE Hiroki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 74 (4) I_1207 - I_1212 2018 [Not refereed][Not invited]
     
     In this study, we investigate the effects of the triangle-shape water surface waves induced by the river antidunes on the stability of concrete block, which is a modelled river revetment work. The water surface waves cannot develop over a fixed flat bed even if we obtain a hydraulic condition, which allows the development of surface waves under a movable bed. The comparision of the block stability experiments between fixed and movable bed under same hydraulic condition therefore obtain the destabilizing effect of the surface wave on the block. The experimental results shows that the presence of the triangle-shape water surface wave significantly destabilizes the block installed on the bed because of the occurance of high velocity induced by the waves and an upward flow from the trough to crest of the antidunes.
  • YAMAGUCHI Satomi, KYUKA Tomoko, SHIMIZU Yasuyuki, IZUMI Norihiro, WATANABE Yasuharu, IWASAKI Toshiki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 74 (4) I_1153 - I_1158 2018 [Not refereed][Not invited]
     
     Large-scale bank erosion caused by channel change during flood often causes serious disasters in gravel bed rivers. In this study, we focused on the influence of sediment dynamics in river channel on the channel change inducing bank erosion. From the results of sediment balance in the Pekerebetsu River and the Otofuke River during a flood, we showed the possibility that sediment supply from the bank affect stream channel change to expand bank erosion in the river. We carried out the experiments on the influence of sediment supply from the bank on the channel change, and showed that sediment supply from the bank can be a cause of channel change inducing large-scale bank erosion.
  • HAMAKI Michihiro, IWASAKI Toshiki, INOUE Takuya, SATO Daisuke, SUMNER Tamaki, SHIMIZU Yasuyuki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 74 (4) I_1033 - I_1038 2018 [Not refereed][Not invited]
     
     Understanding and predicting of the bedload transport processes in rivers are of great importances for better sediment management works. In this study, we propose a numerical model to understand the bedload transport processes by simulating passive bedload tracer particles. A movable bed experiment with the use of colored bedload tracers is performed to understand the advection-dispersion processes of the tracers, i.e., how the tracer particles transport and disperse over the movable bed. We numerically reproduce observed behaviors of the bedload tracers by using a flux-type tracer transport model combined with a two-dimensional bed evolution model. The experimental results suggest that the bedload mixing process associated with a small-scale bedform dominates the advection-dispersion of tracers. The appropriate determination of the active layer thickness by considering this vertical bedload mixing process is necessary to reproduce the tracer advection speed.
  • Yan Qina, Iwasaki Toshiki, Stumpf Andrew, Belmont Patrick, Parker Gary, Kumar Praveen
    EARTH SURFACE PROCESSES AND LANDFORMS 43 (1) 218 - 228 0197-9337 2018/01 [Refereed][Not invited]
  • 岩崎 理樹, 川村 里実, 矢部 浩規
    寒地土木技術研究 : 国立研究開発法人土木研究所寒地土木研究所月報 : monthly report 土木研究所寒地土木研究所 (774) 2 - 10 2432-2652 2017/11 [Not refereed][Not invited]
  • Toshiki Iwasaki, Jonathan Nelson, Yasuyuki Shimizu, Gary Parker
    JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 122 (4) 847 - 874 2169-9003 2017/04 [Refereed][Not invited]
     
    Asymptotic characteristics of the transport of bed load tracer particles in rivers have been described by advection-dispersion equations. Here we perform numerical simulations designed to study the role of free bars, and more specifically single-row alternate bars, on streamwise tracer particle dispersion. In treating the conservation of tracer particle mass, we use two alternative formulations for the Exner equation of sediment mass conservation: the flux-based formulation, in which bed elevation varies with the divergence of the bed load transport rate, and the entrainment-based formulation, in which bed elevation changes with the net deposition rate. Under the condition of no net bed aggradation/degradation, a 1-D flux-based deterministic model that does not describe free bars yields no streamwise dispersion. The entrainment-based 1-D formulation, on the other hand, models stochasticity via the probability density function (PDF) of particle step length, and as a result does show tracer dispersion. When the formulation is generalized to 2-D to include free alternate bars, however, both models yield almost identical asymptotic advection-dispersion characteristics, in which streamwise dispersion is dominated by randomness inherent in free bar morphodynamics. This randomness can result in a heavy-tailed PDF of waiting time. In addition, migrating bars may constrain the travel distance through temporary burial, causing a thin-tailed PDF of travel distance. The superdiffusive character of streamwise particle dispersion predicted by the model is attributable to the interaction of these two effects.
  • 島田 友典, 渡邊 康玄, 岡部 博一, 岩崎 理樹, 中島 康博
    水工学論文集 Annual journal of Hydraulic Engineering, JSCE 土木学会 61 Ⅰ_1345 - 1350 1880-8751 2017 [Not refereed][Not invited]
  • UCHIYAMA Yusuke, ADUMA Kohei, ODANI Sachika, IWASAKI Toshiki, TSUMUNE Daisuke, KAMIDAIRA Yuki, SHIMIZU Yasuyuki, ONDA Yuichi
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 73 (2) I_685 - I_690 1884-2399 2017 [Not refereed][Not invited]
     
    &nbsp;Niida River is well know to supply highly contaminated suspended <sup>137</sup>Cs originated from the Fukushima Nuclear Power Plant to the ocean. We examine the oceanic dispersal and inventories of the sediments and suspended <sup>137</sup>Cs in the ocean floor derived from Niida River, using the quadraple nested JCOPE2-ROMS 3D circulation model in a very high resolution configuration, coupled with a 3D multi-class sediment transport model, the iRIC-Nays 2DH river sediment model, the SWAN spectral wave model, and a static <sup>137</sup>Cs absorption model. We focus on the storm and flood event associated with Typhoon 201326 (Wipha) passed off the Fukushima Coast, which provoked an enomous amount of riverine fluxes, to quantitatively assess the accumulation and erosion of the sediments and resultant suspended <sup>137</sup>Cs inventories around the river mouth and nearshore areas.
  • SHIMADA Tomonori, WATANABE Yasuharu, OKABE Kazuhiro, IWASAKI Toshiki, NAKASHIMA Yasuhiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 73 (4) I_1345 - I_1350 2017 [Not refereed][Not invited]
     
    &nbsp;It is important mitigating flood damage by overflow from a levee breached. The mechanism of levee breach has not been clarified. This study aims to clarify the below point, the effect of channel width and channel bed profile on levee breach processes by using a numerical model to simulate levee breaches based on results of the experiments. The results of the simulation are as follows: In the case of steep slope channel, levee breach widening is dominant. In the case of mild-slope channel, river bed erosion is dominant.
  • IWASAKi Toshiki, INOUE Takuya, YABE Hiroki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 73 (4) I_901 - I_906 2017 [Not refereed][Not invited]
     
    &nbsp;This study presents a modeling of three-dimensional river antidunes using a Boussinesq model with a non-equilibrium bedload transport model, and discuss the relation of this three-dimensional bedform instability to the triangle-shape water surface wave trains. We performed a linear stability analysis of the three-dimensional antidunes, showing that the proposed model in part reproduces the three-dimensionality of the antidunes. The dominant longitudinal and transverse wave numbers predicted by the analysis are reasonably in agreement with the characteristics of the triangle-shape water surface wave trains, although the model tends to overestimate the wavelength of the water surface waves.
  • T. Inoue, T. Iwasaki, G. Parker, Y. Shimizu, N. Izumi, C. P. Stark, J. Funaki
    JOURNAL OF HYDRAULIC ENGINEERING 142 (7) 0733-9429 2016/07 [Not refereed][Not invited]
     
    Natural bedrock rivers exhibit diverse erosional morphologies. Although the formation of alternate bars on bedrock has been noted in previous studies, the influence of these alternate bars on bedrock erosion has not been clarified. In this study, the authors propose a model for bedrock-alluvial channels that reproduces both bar formation and erosional morphology. In addition, the authors report on numerical simulations to evaluate the influence of sediment supply on the state of the bed at and over the bedrock surface. The numerical results illustrate the formation of different morphologies for different supply rates. When the sediment supply rate is close to transport capacity, mixed alluvial-bedrock alternate bars form. These bars are analogous to purely alluvial alternate bars. A meandering thread of alluvial material migrates downstream over a uniformly eroding bedrock surface. When the sediment supply rate is well below capacity, however, multiple incisional troughs (grooves) form on the bedrock surface, and alluvial cover tends to concentrate in the troughs.
  • Toshiki Iwasaki, Yasuyuki Shimizu, Ichiro Kimura
    ADVANCES IN WATER RESOURCES 93 118 - 134 0309-1708 2016/07 [Refereed][Not invited]
     
    Recent studies suggest that braided river could be single-thread channel by colonization of riparian vegetation; however, this kind of mutual interactions between physical and ecological processes in rivers are still poorly understood. Here we investigate the development of meandering channel in a river, which was originally braided and currently vegetated, the Otofuke River in Japan. The significant morphological processes of this river during a destructive flood event was studied using a two-dimensional morphodynamic model. Using well-calibrated parameters, this model qualitatively reproduced observed morphological changes such as the co-development of sand bars, bar-induced meandering and a chute cutoff. We find that for vegetated channels, meandering could maintain moderate sinuosity; in contrast, in the absence of riparian vegetation, bar-induced meandering channels could become braided. This suggests that distinct meandering channels could be a fundamental channel morphology in the originally braided, but currently vegetated river; however, the simultaneous occurrence of the chute cutoff and meandering indicates that this channel could not be a fully-developed high amplitude meandering channel. (C) 2015 Elsevier Ltd. All rights reserved.
  • Jonathan M. Nelson, Yasuyuki Shimizu, Takaaki Abe, Kazutake Asahi, Mineyuki Gamou, Takuya Inoue, Toshiki Iwasaki, Takaharu Kakinuma, Satomi Kawamura, Ichiro Kimura, Tomoko Kyuka, Richard R. McDonald, Mohamed Nabi, Makoto Nakatsugawa, Francisco R. Simoes, Hiroshi Takebayashi, Yasunori Watanabe
    ADVANCES IN WATER RESOURCES 93 62 - 74 0309-1708 2016/07 [Refereed][Not invited]
     
    This paper describes a new, public-domain interface for modeling flow, sediment transport and morphodynamics in rivers and other geophysical flows. The interface is named after the International River Interface Cooperative (iRIC), the group that constructed the interface and many of the current solvers included in iRIC. The interface is entirely free to any user and currently houses thirteen models ranging from simple one-dimensional models through three-dimensional large-eddy simulation models. Solvers are only loosely coupled to the interface so it is straightforward to modify existing solvers or to introduce other solvers into the system. Six of the most widely-used solvers are described in detail including example calculations to serve as an aid for users choosing what approach might be most appropriate for their own applications. The example calculations range from practical computations of bed evolution in natural rivers to highly detailed predictions of the development of small-scale bedforms on an initially flat bed. The remaining solvers are also briefly described. Although the focus of most solvers is coupled flow and morphodynamics, several of the solvers are also specifically aimed at providing flood inundation predictions over large spatial domains. Potential users can download the application, solvers, manuals, and educational materials including detailed tutorials at www.-i-ric.org. The iRIC development group encourages scientists and engineers to use the tool and to consider adding their own methods to the iRIC suite of tools. Published by Elsevier Ltd.
  • Toshiki Iwasaki, Yasuyuki Shimizu, Ichiro Kimura
    ADVANCES IN WATER RESOURCES 92 57 - 72 0309-1708 2016/06 [Refereed][Not invited]
     
    A number of numerical models have been proposed to understand and simulate fluvial river morphodynamics; however, it is somewhat unclear whether all the models are able to consistently simulate flow-bed instability phenomena. This study investigates the sensitivity of free bar morphology in rivers to secondary flow models used in depth-averaged models using linear stability analyses and numerical simulations. Both the linear analyses and numerical simulations suggest that under certain hydraulic conditions, an equilibrium-type secondary flow model, which has been widely used in river morphodynamic models, fails to generate a finite wavelength and bar mode, allowing the inception of bars of infinitely short scale and infinitely high mode. Using a nonequilibrium-type secondary flow model avoids the un-physical formation of these incipient free bars, and gives better solutions regarding finite amplitude bars. Since free bars are essential, intrinsic river morphological features, the findings of this study can be applied to a wide range of river morphodynamic calculations. (C) 2016 Elsevier Ltd. All rights reserved.
  • YAMANISHI Takafumi, UCHIYAMA Yusuke, IWASAKI Toshiki, SHIMIZU Yasuyuki, TSUMUNE Daisuke, MISUMI Kazuhiro, ONDA Yuichi
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 公益社団法人 土木学会 72 (2) I_757 - I_762 1884-2399 2016 [Not refereed][Not invited]
     
    &nbsp;We examine oceanic dispersal of the iRIC-Nays2DH-evaluated sediment and suspended <sup>137</sup>Cs influxes from Niida River, Fukushima, with a particular attention to the first flood event in late May of 2011 after the Fukushima nuclear accident. Alongshore suspended <sup>137</sup>Cs transport occurs assymetrically, comprising storm-driven southward transport confined in the shallow area due to shoreward Ekman transport associated with strong northerly wind, followed by northwestward widespread transport under mild southerly wind condition. About 70 % of the Niida River-derived suspended <sup>137</sup>Cs remains near the mouth for 20 days after the flood event. Nevertheless, our model results as well as an observation suggest that the area is dominated by erosion as for high bed shear stress all the time, thus suspended radionuclides are redistributed to dissipate away in long term.
  • INOUE Takuya, IWASAKI Toshiki, ONDA Shinichiro
    Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)) 公益社団法人 土木学会 72 (2) I_565 - I_574 2016 [Not refereed][Not invited]
     
    Dynamics of river bedforms which is an interfacial instability phenomenon between turbulent open channel flow and movable bed significantly affect the flow structures and sediment transport dynamics in rivers, so that this have been an classical and important research topic in the field of river engineering. Here, we perform a linear stability analysis for several combinations of flow and sediment transport submodels, specifically, a shallow flow model and a Boussinesq type depth-integrate model for hydrodynamic model, and an equilibrium and a non-equilibrium bedload transport model for sediment mass conservation model. We then investigate how the submodels adopted determine the linear stability and the wavelength of river bedforms. The results show that the combination of the Boussinesq model and the non-equilibrium bedload transport model can explain the antidune instability and its finite wavelength observed in several published experiments, whereas, use of each submodel alone is insufficient to explain the finite wavelength of antidunes.
  • F. Schuurman, Y. Shimizu, T. Iwasaki, M. G. Kleinhans
    GEOMORPHOLOGY 253 94 - 109 0169-555X 2016/01 [Not refereed][Not invited]
     
    River meandering results from spatially alternating bank erosion and bar growth. Recent flume experiments and theory suggest that a continuous inflow perturbation is a requirement for sustained meandering. Furthermore, flume experiments suggest that bar-floodplain conversion is an additional requirement. Here, we tested the effects of continuous inflow perturbation and bar-floodplain conversion on meander migration using three numerical morphodynainic models: a 1D-model, and two 2D-models with one of them using adaptive moving grid. We focused on the interaction between bars and bends that leads to meander initiation, and the effect of different methods to model bank erosion and floodplain accretion processes on meander migration. The results showed that inflow perturbations have large effects on meander dynamics of high-sinuosity channels, with strong excitation when the inflow is periodically perturbed. In contrast, inflow perturbations have rather small effect in low-sinuosity channels. Steady alternate bars alone are insufficient to cause high-sinuosity meandering. For high-sinuosity meandering, bar-floodplain conversion is required that prevents chute-cutoffs and enhances flow asymmetry, whilst meandering with chute-cutoffs requires merely weak floodplain formation, and braiding occurs without floodplain formation. Thus, this study demonstrated that both dynamic upstream inflow perturbation and bar-floodplain conversion are required for sustained high-sinuosity meandering. (C) 2015 Elsevier B.V. All rights reserved.
  • AKAHORI Ryosuke, AKAMATSU Yoshihisa, IWASAKI Toshiki, INUI Ryutei, NAGANO Hiroyuki, KAMITSURU Shogo
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 71 (4) I_1471 - I_1476 1880-8751 2015 [Not refereed][Not invited]
     
    Semimountainous areas in Yamaguchi and Shimane Prefectures suffered severe damage brought by floods on July 2013. The damages in these areas were characterized by the vulnerability of their backlands that consists of agricultural lands. In order to investigate the mechanisms of land erosion on these areas where existing high-resolution data was not prepared, post-disaster RTK-GPS surveys and numerical simulations were conducted for Abu River in Yamaguchi. The surveys were aimed at providing the high-resolution topographic datasets of these regions in order to evaluate the influences of micro-topography on channel incisions by the flood flow. The results of the numerical calculations of movable bed-evolution well reproduced the process of the channel incisions on these areas, and it implies that the micro-topography is one of the most influential factors on erosion and channel formation processes on such semimountanious regions.
  • IWASAKI Toshiki, PARKER Gary, SHIMIZU Yasuyuki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 71 (4) I_877 - I_882 2015 [Not refereed][Not invited]
     
    This paper presents numerical simulations of tracer particle transport both in the absence and presence of free bars. The transport and diffusion of tracer particles is affected by both the probabilistic motion of sediment particles and by the river bed geometry associated with free bars. We compare results of numerical models using an equilibrium (flux-based model) and a non-equilibrium (entrainment-based model) conservation formulation for river bed variation associated with bedload transport. The results show that 1) the entrainment-based morphodynamic model successfully reproduces free bar formation, 2) the flux-based morphodynamic model fails to simulate tracer diffusion in the absence of bars, and 3) free bar formation enhances streamwise tracer diffusion.
  • T. Iwasaki, M. Nabi, Y. Shimizu, I. Kimura
    JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 139 416 - 426 0265-931X 2015/01 [Not refereed][Not invited]
     
    A numerical model capable of simulating the transfer of Cs-137 in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium (Cs-134, Cs-137) and radioiodine (I-131) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the Cs-137 contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated Cs-137 contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most Cs-137 supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented Cs-137 supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented Cs-137 behavior in rivers. (C) 2014 Elsevier Ltd. All rights reserved.
  • IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 70 (4) I_1267 - I_1272 1880-8751 2014 [Not refereed][Not invited]
     
    A numerical model for calculating the behavior of radioactive contaminant associated with the sediment transport in rivers has been proposed in this study. The equations for simulating the concentration of radioactive contaminant of the sediment has been derived from the governing equation of the sediment transport model. The proposed model has been applied to a simple river confluence to understand the mixing process of the sediment and the radioactive contaminant in the confluence point. The numerical results provide a useful data for discussing the relation between the bed evolution process and the behavior of radioactive contaminant. In addition, the model can contribute to estimate the origin of the sediment by using the relationship between the simulated sediment diameter and the concentration of the radioactive contaminant.
  • M. Nabi, S. Giri, T. Iwasaki, I. Kimura, Y. Shimizu
    RIVER FLOW 2014 1253 - 1259 2014 [Not refereed][Not invited]
     
    We developed a morphodynamic model for generation and migration of dunes under shallow flow approximation. The flow was calculated by two-dimensional depth-averaged equations and the bed shear stress was found by fitting a log-low function at each grid cell. The shear stress then was adjusted by adding slope effect. As the bed features have smaller spatial scales than the flow, a two-grid approach is adopted. The flow is solved on a coarse grid and then the flow field is interpolated on a finer grid, on which the bed morphology is calculated. This technique enabled us to solve the morphological process for large scale applications. A parameterized relation is applied for bedload sediment transport and the bed evolution is updated using Exner equation. Two cases with different flow conditions are simulated and compared with experimental results and field measurements. The computed results show good agreement with experiments and field measurements.
  • R. Suzuki, I. Kimura, Y. Shimizu, T. Iwasaki, T. Hosoda
    RIVER FLOW 2014 179 - 187 2014 [Not refereed][Not invited]
     
    The secondary current of the second kind, which is initiated by the turbulence anisotropy, is a classical topic in fluid engineering and has been studied by many researchers with wide variety of methods. However, we have still controversy on this phenomenon, in particular, the secondary currents in open channels with larger aspect ratio (=B/h > 5, B: channel width, h: water depth). This paper investigated the fundamental characteristics of the secondary current of the second kind in wide shallow open channel flows through the comparison between 3-D (three-dimensional) URANS (Unsteady Reynolds Averaged Navier Stokes Equations) computations and results of laboratory experiments performed by Blanckaert et al. (2010). A second order non-linear k-epsilon model proposed by Ali et al. (2007) was employed as a turbulence model. First, we tried to carry out the computations under the same conditions of the laboratory tests by Blanckaert et al. We employed three cases in rectangular open channels with different depths for validating the numerical model. The computational results are generally in good agreement with the experimental results not only the cross-sectional secondary flow patterns but also patterns of Reynolds stresses and turbulence kinetic energy. The experimental results showed that the periodic vortices with streamwise axes are generated regularly in the cross section except the vicinity of side walls, and their diameter is almost same as the water depth. It means that the larger vortices are generated in case of larger depth. The same tendency was well simulated by the present computations. It has been pointed out in previous papers that the secondary currents of straight open channels are initiated by the surface vortex and the bottom vortex near the side walls, and the secondary current becomes weaker as the distance from the side wall increases. It has been reported that the clear secondary current is not generated at the region where the distance from the side wall is larger than 2.5 h (e.g., Nezu et al., 1985). However, such damping of vortex strength was not observed in the present computations as well as the experiments by Blanckaert et al. In order to check the effect of side walls to the secondary current, we performed the computation under the aspect ratio = 100. In this case, the secondary currents are again generated clearly in the whole channel and no damping effect is observed in the middle part. The result was also same even if a periodic boundary condition is adopted in the lateral direction to neglect completely the effect of side walls. Those results imply an important finding that the surface and bottom vortices near the side walls, which have been considered to drive the secondary current cells, are not a necessary source for generating secondary currents in entire cross section of a shallow straight open channel.
  • Toshiki Iwasaki, Yasuyuki Shimizu, Ichiro Kimura
    PROCEEDINGS OF THE INSTITUTION OF CIVIL ENGINEERS-MARITIME ENGINEERING 166 (2) 76 - 88 1741-7597 2013/06 [Refereed][Not invited]
     
    The physical and numerical modelling of the initiation and development process of tidal creek network in tidal environments is presented herein. An attempt was made to reproduce the developing process of tidal creeks on a small experimental flume by considering the scaling rules of flow and sediment transport associated with tidal flows between the real scale and an experimental flume. In the experiments, the initial stage of channel evolution and the complex channel network configuration were successfully modelled, and results show that the similar network geometry observed in tidal environments can be reproduced at an experimental scale. Numerical simulations of initiation and development of tidal creeks were also undertaken using a two-dimensional-based morphodynamic model. The results indicated that the proposed numerical model simulated the geometry of channel network and its development process observed in the experiment reasonably well. In addition, a sensitivity analysis of grid resolution was carried out to show how grid resolution affected the computational results. The results implied that a grid size which can resolve the finer-scale channels that form in the initial stages of network development is required to simulate the evolution of tidal creeks adequately.
  • 木村 一郎, 山蔦 涼, 岩崎 理樹
    水工学論文集 土木学会水工学委員会 編 土木学会 57 1_643 - 648 1880-8751 2013 [Not refereed][Not invited]
  • IWASAKI Toshiki, OKUDERA Ryota, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 69 (4) I_1093 - I_1098 2013 [Not refereed][Not invited]
     
    This paper presents a consideration of formation mechanism of tidal channel networks. We employed a simple mathematical model to explain the flow and bed evolution in intertidal zones. By assuming the regular periodic tidal wave and the simple bed geometry which has constant slope, we derived an advection - diffusion equation for the bed evolution. This equation has a Peclet type non dimensional number which expresses the ratio between advection and diffusion. We investigated this Peclet number in the experimental results conducted under the different hydraulic conditions. The results show that in the conditions with small Peclet number, which means that the diffusion effect is relatively strong, clear channel network can not develop on the bed surface. On the other hand, in large Peclet number conditions, clear and complicated channel network tends to develop.
  • KIMURA Ichiro, YAMATSUTA Ryo, IWASAKI Toshiki, SHIMIZU Yasuyuki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 69 (4) I_643 - I_648 2013 [Not refereed][Not invited]
     
    A multi-level grid type turbulent shallow flow model combined with an equilibrium sediment transport model (KMR-MB: Kinematic Mesh Reconstruction for Movable Bed) is proposed. KMR method is a kind of multi-level grid model with dynamic refinement and combining grid cells to capture efficiently unsteady flow phenomena. Saito et al. (2012)1) have applied the KMR approach to open channel flows around a bridge pier and shown the advantage of the model. They used the maximum value of the strain and rotation parameters for the threshold for quad-tree and 3 x 3 type grid divisions. We have extended the model for computations of morphological phenomena in rivers by incorporating an equilibrium sediment transport model as well as a bed continuity equation, and employing new criteria for grid cell refinement. We employed an average curvature of the bed surface as the criteria for refinement and combining quad-tree type grid cells. The present model has been applied to simulate the alternative bar formations. The experimental result by Akahori et al (2011)2) was used for validation of the model. The comparison between numerical and experimental results showed that the present KMR-MB can simulate excellently the phenomena with less CPU time than the fixed grid computations.
  • IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 69 (3) 123 - 134 2013 [Not refereed][Not invited]
     
    &nbsp;The performance and stability of a numerical model which consist of a shallow water flow model and an equilibrium bedload transport model for calculating bed evolution in rivers is discussed. Such system equations which are generally adopted for calculating reach-scale river bed evolution have a hyperbolic feature. This fact has implied that upwind schemes to the space derivative of bedload transport in Exner equation are useful numerical methods to avoid bed instabilities in calculating the propagation of a small disturbance. Whereas, a bed diffusion effect which is essentially included in bedload dominated bed evolution has been modelled in equilibrium bedload transport models by considering the local slope effect to the bedload transport. The relation between the numerical and physical diffusion effect to the bed evolution should be investigated to understand the performance and stability of the model. A hyperbolic differential equation controlling the bed evolution was derived from the linearized system equations to understand the numerical characteristic of the propagation of the bed disturbance. We defined a P&eacute;clet number, <i>P<sub>e</sub></i>, as the ratio between the advective effect which controls the propagation of the bed disturbance and the diffusive effect associated with the bed slope effect. The effect of physical diffusion of the bed exceeds the effect of numerical diffusion by the upwind scheme to the bedload transport in the condition which <i>P<sub>e</sub></i> < 2. The series of computations which focus on the propagation of hump type bed disturbance were conducted. The numerical results show that the calculation of propagating the bed disturbance can be physically stable without the upwind scheme when the grid size which satisfies <i>P<sub>e</sub></i> < 2 is used. The grid size which is required such physically stable computation depends on how the bed slope effect is modelled in the bedload transport model.
  • IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 69 (3) 147 - 163 2013 [Not refereed][Not invited]
     
    &nbsp;This paper investigates an influence of the modelling of secondary flows to the formation and development of free bars in rivers by comparing the results of the numerical simulation, the linear stability analysis and the experiments. Free bars which are developed by a physical instability phenomenon between turbulent flow and bed surface of rivers are one of fundamental river morphologies. Theoretical studies by the linear stability analysis have successfully shown that two dimensional morphodynamic models for calculating the river bed evolution can explain the formation of free bars. However, three dimensional flow structures, for instance, secondary flows caused by the meandering flows with increasing the bar height, have also important roles in the dynamics of free bars on a nonlinear level. Although quasi-three dimensional flow models can be a powerful tool to include the three dimensionalities of flows on the framework of two dimensional approaches, the applicability of such models to the dynamics of free bars has not been well verified yet. The results of the linear stability analysis suggested that the model of secondary flows which is assumed under the fully developed stage allows developing the bar with unrealistically high mode. This high mode bar tends to develop under the hydraulic conditions in which the effect of transverse slope for the sediment transport direction is relatively weak. Such instability can be physically suppressed by applying a model of secondary flows which includes the effect of development of secondary flows. The results of numerical simulation shows that proposed model which considers the development of the secondary flows can reasonably reproduce the incipient of free bars which is indicated from the linear stability analysis as well as the equilibrium bar waveheight in the experiments.
  • TANAKA Toshiyuki, SHIMIZU Yasuyuki, NELSON Jonathan, IWASAKI Toshiki
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 68 (4) I_1033 - I_1038 2012 [Not refereed][Not invited]
     
    The Great Mississippi Flood of 1927 was the most destructive river flood in the history of the United States. After the flood in 1927, Mississippi River and Tributaries Project has carried out and changed the engineering policy. One of the biggest projects in MR&T project is the constriction of Birds Point-New Madrid Floodway. In 2011, May, Mississippi River had flooded dramatically and floodway had used which have not been used since 1937. By using floodway smoothly, explosion of levee had executed which was including in Birds Point-New Madrid Floodway operation measure. On our research, we evaluate the effect of the floodway and reproduce the flood by using numerical simulation. By our simulation, floodway has the effect to reduce the water level 1.5m~3m. We also simulate the characteristics of the floodway.
  • IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 68 (4) I_979 - I_984 2012 [Not refereed][Not invited]
     
    This study presents the numerical simulations of initiation and development process of tidal creek network by using two-dimensional morphodynamic model including the seepage flow model, and also discusses the effect of seepage flow for development of tidal creek network. A two dimensional shallow flow equation and two dimensional saturated seepage flow model based on Darcy law were combined to simulate flow field both on and in the bed. The numerical tests with and without seepage flow model were carried out to understand the effect of seepage flow for development of tidal creek in simplified conditions. The result shows that, by including seepage flow model, the channel network tend to become complex one, which has a lot of small scale channels. In addition, the channel width and depth increases by the very shallow flows induced by water supply from inside the bed. This indicates that the seepage flow from inside the bed can have dominant effect for morphodynamics on tidal areas, especially in case of subjecting the dry and wet condition in the bed surface.
  • ZENNO Hiroki, IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 68 (4) I_865 - I_870 2012 [Not refereed][Not invited]
     
    It is important from the engineering point of view to predict the collapsing process of river embankment and behavior of overtop flow for reducing disaster during flood. We performed some considerations on refinement of a two-dimensional computational model based on shallow flow equations to predict more accurately the front overflow levee breach phenomena. We tried to introduce a levee erosion model instead of sediment transport model to evaluate the deformation of the levee. In addition, intermittent behavior of the bank collapse is modeled. A calibration of the numerical model is made through the comparison with field experimental data. Recently, a real-scale experiment on a front levee breach was carried out at the Chiyoda Experimental Channel in Hokkaido, Japan. We performed the computation under the same conditions in the experiment. The computational results showed that the present refined model can predict fundamental aspects of the front levee breach phenomena. breach phenomena.
  • Numerical simulation on bed evolution and channel migration in rivers
    Toshiki Iwasaki, Yasuyuki Shimizu, Ichiro Kimura
    RIVER FLOW 2012, VOLS 1 AND 2 673 - 679 2012 [Refereed][Not invited]
     
    This paper presents the numerical simulation of sand bar evolution with bank erosion in the Otofuke river, Hokkaido, Japan. A great flood occurred in the Otofuke River, at Hokkaido region in September 6th, 2011 have caused the significant bed evolution and channel migration. As a result, a part of the river embankment was destroyed. To protect such damage of the river embankment during the flood, the complex interaction between flow, bed evolution and bank erosion in rivers have to be investigated. In this study, the flow and bed deformation of the Otofuke river during the flood was examined by using a depth-averaged two-dimensional morphodynamic model. The numerical result indicates that the alternate sand bars developed in low water channel at peak discharge and these sand bars creates the clear alternative thalweg. By the concentration of flows in the thalweg, the significant channel migration might occur during falling stage of discharge. This implies that unsteadiness of discharge is a one of key role to bank erosion process in case of co-existing of sand bars.
  • Geomorphological characteristics of female and male-type meanders
    Kozue Tanaka, Yasuyuki Shimizu, Satomi Yamaguchi, Toshiki Iwasaki, Ichiro Kimura, Gaku Tanaka
    7th IAHR Symposium on River, Coastal and Estuarine Morphodynamics(CD-ROM) 7 1824 - 1831 2011 [Refereed][Not invited]
  • IWASAKI Toshiki, WATANABE Yasunori, OKUDERA Ryota, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 土木学会 67 (2) 951 - 955 1884-2399 2011 [Not refereed][Not invited]
     
    The complex channel networks have dominant roles for flow, sediment and nutrient transport on salt marshes and tidal flats, and therefore provide rich habitat structures. This study discusses the fundamental geometric properties of tidal channel network by statistical analysis to their channel length and planimetric shapes. We employed channel networks which delineated from experimental and numerical result and also satellite image of real field. It is found that the probability density distribution of channel length can be described by a lognormal distribution, and network in experimental and real scale have similar properties for channel length. The results also indicate that the difference of tidal conditions change the characteristics of tidal channel network configuration.
  • TANAKA TOSHIYUKI, SHIMIZU YASUYUKI, KIMURA ICHIRO, IWASAKI TOSHIKI
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 67 (4) I_895 - I_900 2011 [Not refereed][Not invited]
     
    The urbanization in Sapporo was started about only 140 years ago. Before the urbanization, the topography of most part of Sapporo was wetland and not suitable for living and cultivation. Intensive river training works have changed this area dramatically for relatively short period, and made Sapporo as one of the biggest cities in Japan with a population of 1.9 million. In this study, the history of river training works and the transition of inundation characteristics in Sapporo are investigated through old literatures and numerical simulations. First, the historical process of river training constructions was clarified by inspecting old documents and found out some key works. Then numerical simulations of flood were performed in three cases, namely, original topography, after construction of Toyohira-River- Bank and after construction of new Toyohira River Channel. The comparison of simulation results elucidated the relation between river training works and change of inundation behavior.
  • IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 67 (4) I_859 - I_864 2011 [Not refereed][Not invited]
     
    This paper presents the laboratory tests on developing process of tidal creek network in the small flume and also validation of numerical model which can replicate the morphodynamic evolution of tidal channel and its geomorphic features. The experimental conditions fully satisfied the kinematic, dynamic and sediment transport similarities between the real and experimental scale. The channel network, which has the similar channel characteristics such as ratio between the channel width and depth observed in real field, was reproduced in the experimental flume. This study also conducted the numerical simulations with experimental conditions for validating the physically-based two-dimensional morphodynamic model. The results showed that the proposed morphodynamic model can simulate reasonably the geometry of channel network and its developing process observed in the experiment.
  • ZENNO Hiroki, IWASAKI Toshiki, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 67 (4) I_853 - I_858 2011 [Not refereed][Not invited]
     
    Flood in rivers is a common disaster all over the world. If a levee breach happens, it sometimes causes a fatal disaster. In addition, many buildings, urban facilities, lifelines, etc. are seriously damaged. Detailed mechanism of a levee breach has not been clarified yet. Therefore, it is important to predict the collapsing process of riverbank and behavior of overtop flow for reducing damage. We applied a two-dimensional shallow flow computational model to levee breach phenomena caused by overflow and the performance of the model was elucidated. A calibration of the numerical model is made through the comparison with field experimental data. Recently, a real-scale experiment on a levee breach was carried out at the Chiyoda Experimental Channel in Hokkaido, Japan. We performed the computation under the same conditions in the experiment. The computational results showed the excellent performance for simulating levee breach phenomena.
  • OIKAWA Shin, IWASAKI Toshiki, YAMAGUCHI Satomi, SHIMIZU Yasuyuki, KIMURA Ichiro
    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 公益社団法人 土木学会 67 (4) I_751 - I_756 2011 [Not refereed][Not invited]
     
    The bed degradation is going rapidly in the upper part of the Ishikari River recently, owing to exposed bedrock erosion caused by bedload on the bedrock. In order to estimate the erosion rate of bedrock, we performed an experiment by a circular channel flume with artificial bedrock made of plaster. We applied the erosion rate estimated by the present experiment to a numerical simulation of bed deformation on the bedrock by using horizontal 2D flow model and the bedload layer model. The result of the simulation shows that gut pattern appeared in the simulated results which is very similar to the experimental result. It was found that the bed degradation was progressed by the erosion caused by sediment transport itself.
  • Toshiki Iwasaki, Yasuyuki Shimizu, Ichiro Kimura
    International Journal of River Basin Management 9 237 - 245 1571-5124 2011/01/01 [Not refereed][Not invited]
     
    This paper discusses the bed evolution and the grain sorting process in meandering channel by using a two-dimensional (2D) based morphodyamic model. In river bends, secondary currents, which are three-dimensional (3D) flow structures caused by a balance between centrifugal force and pressure gradient, has important roles for flow structure and the sediment transport. Therefore, a numerical model, which can reproduce this 3D flow structure, is required to describe the morphodynamic phenomena in meandering rivers. This study employed the depth-averaged 2D shallow water equations’ integrated effect of secondary currents of the first kind for flow calculations. This flow model can consider the effect of lag between the developments of secondary current and streamline curvatures. In addition, we employed the equilibrium sediment transport model and a multiple layer model for simulating the sediment transport and sorting phenomena due to non-uniform sediments. This study applied the different kind of model for evaluating the secondary current and sediment transport to a meandering channel with simple-rectangular sine-generated curve. We examined the applicability of models and morphodynamic process in a meandering channel through the comparison between the experimental and numerical results. The result shows that the correlation for secondary currents for flow structures and sediment transport is important to reproduce the bed evolution and sorting phenomena in river bends. © 2011 International Association for Hydro-Environment Engineering and Research.
  • 岩崎理樹, 清水康行, 木村一郎, 田中岳
    水工学論文集(CD-ROM) 53 ROMBUNNO.125  1880-8751 2009/02 [Refereed][Not invited]
  • MASUYA Shigekazu, SHIMIZU Yasuyuki, IWASAKI Toshiki
    PROCEEDINGS OF HYDRAULIC ENGINEERING 公益社団法人 土木学会 52 607 - 612 0916-7374 2008 [Not refereed][Not invited]
     
    This study aims to develop a physically-based morphodynamic model in order to reproduce incision of tidal creek networks as well as evolution of geomorphology in the tidal environments. The process of incision and long-term geomorphologic evolution on tidal flats and marsh is of practical significance from the environmental view point. Generally, it is postulated that tidal creeks are developed as a result of ecomorphologic processes of tidal system driven by tidal energy. Some previous investigations have provided significant insight to this problem. However, there is still lack of a physically-based modeling approach that can replicate the initiation and evolution process of this phenomenon. In this study, physically-based model was applied to a narrow area referred to as tidal flats in order to provide quantitative and qualitative evaluation of its reproducibility. Calculation was conducted for different time scale up to 350 days. Calculation results revealed that the incision of tidal network and its initial development process can satisfactorily be reproduced by a physically-based computational model.
  • IWASAKI Toshiki, SHIMIZU Yasuyuki
    Journal of applied mechanics 公益社団法人 土木学会 11 745 - 752 1345-9139 2008 [Not refereed][Not invited]
     
    In this paper, eco-morphological model is proposed to simulate morphology at tidal environment with vegetation growth. Two numerical experiments such as vegetated scenario and unvegetated scenario were performed to clarify influence of vegetation on morphological evolution. This model was applied to a square tidal flat and calculations were conducted for 350 days. Computational results show that a complicated channel network is formed on tidal marsh and natural levees were appeared around the channel network in both cases. In addition, the vegetation propagated along the natural levees. In vegetated scenario, sediment deposition was enhanced by effect of vegetation on natural levee in comparsion with unvegetated scenario. Therefore, these results indicated that tidal channels are formed more clearly due to vegetation.

MISC

Awards & Honors

  • 2019/11 Committee on Hydroscience and Hydraulic Engineering Best paper award of annual conference on Hydraulic Engineering JSCE
     
    受賞者: Toshiki Iwasaki
  • 2018/05 北海道開発局 北海道開発技術研究発表会 寒地土木研究所長賞
     
    受賞者: 岩崎理樹
  • 2015/06 土木学会 土木学会論文奨励賞
     
    受賞者: 岩崎理樹
  • 2013/03 土木学会 水工学委員会 水工学論文奨励賞
     
    受賞者: 岩崎理樹
  • 2010/03 土木学会 北海道支部 土木学会北海道支部年次講演会優秀学生講演賞
     
    受賞者: 岩崎理樹
  • 2008/03 北海道大学 土木工学科 廣井賞
     
    受賞者: 岩崎理樹
  • 2006/03 苫小牧工業高等専門学校 環境都市工学科 近藤賞
     
    受賞者: 岩崎理樹

Research Grants & Projects

  • シームレス広域土砂輸送-地形変動モデルの構築と流域内の水土砂災害への脆弱性評価
    Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists
    Date (from‐to) : 2020/04 -2023/03 
    Author : 岩崎 理樹
  • 大量アンサンブル降雨―流出計算データを利用した流路変動解析による河道被災リスクの定量評価手法の構築
    国土交通省水管理・国土保全局:河川砂防技術研究開発 河川技術部門
    Date (from‐to) : 2020/05 -2021/03 
    Author : 清水康行,泉典洋,今日出人,山田朋人,久加朋子,星野剛,山口里実,井上卓也
  • 混濁流による高流砂階のベッドフォームの堆積構造解明と堆積モデルの構築
    文部科学省:科学技術研究費補助金 基盤研究(B)
    Date (from‐to) : 2018/04 -2021/03 
    Author : 横川美和
  • 令和元年台風19号及び台風21号による広域災害に関する総合研究
    Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Special Purposes
    Date (from‐to) : 2019/12 -2020/03 
    Author : 二瓶 泰雄, 中北 英一, 竹見 哲也, 山田 朋人, 三隅 良平, 飯塚 聡, 鈴木 真一, 仲江川 敏之, 柳瀬 亘, 立川 康人, 田中 茂信, 佐山 敬洋, 田中 智大, 朝位 孝二, 前野 詩朗, 田中 仁, 吉谷 純一, 田中 規夫, 泉 典洋, 矢野 真一郎, 森脇 亮, 赤松 良久, 内田 龍彦, 重枝 未玲, 岩崎 理樹, 清水 義彦, 小山 毅, 長谷川 兼一, 西嶋 一欽, 藤本 郷史, 毛利 栄征, 前田 健一, 岡村 未対, 卜部 厚志, 森口 周二, 蝦名 裕一, 松四 雄騎, 王 功輝, 竹林 洋史, 鈴木 素之, 田島 芳満, 佐々木 淳, 信岡 尚道, 森 信人, 有川 太郎, 鈴木 崇之, 下園 武範, 松井 正宏, 小林 文明, 畑山 満則, 牛山 素行, 佐藤 健, 梶谷 義雄
  • 土砂トレーサーを利用した土砂動態-地形変動過程の理解と予測
    文部科学省:科学技術研究費補助金 若手研究
    Date (from‐to) : 2017/04 -2020/03 
    Author : 岩崎理樹
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2015/04 -2018/03 
    Author : Yokokawa Miwa, IWASAKI Toshiki, OHISHI Yuri, OHATA Koji, HUGHES CLARKE John, PARKER Gary, TALLING Peter, CARTIGNY Matthieu
     
    Recent field observation revealed that there are abundant “cyclic steps” (CS) formed by turbidity currents (TC) in the submarine channels and their vicinity. Here we did the first experiments on the formation of CS due to the “surge-type” TCs, and showed that the “surge-type” TCs can form CS easier compare with the continuous TC which has equivalent unit-time discharge. Experimental TCs, which is mixture of plastic particles and salt water, were released to the 7-m-long flume at Osaka Institute of Technology, with the surge durations 3, 5, 7 seconds. 130-140 surges were released into the flume for each case, and 5-6 CS were formed. Based on these experimental results, analytical analysis and numerical simulation were performed. In addition, we applied the experimental results to rock records. We made a depositional model for the sediment waves observed in turbidites in the Miyazaki Group, Kyusyu, Japan, based on the extensive long-distance drawing of the sedimentary structures.
  • 感潮域における持続可能な環境保全手法の確立に向けた地形変動予測モデルの開発
    文部科学省:科学技術研究費補助金 特別研究員奨励費
    Date (from‐to) : 2010/04 -2013/03 
    Author : 岩崎理樹


Copyright © MEDIA FUSION Co.,Ltd. All rights reserved.