関根　正人

ISSN：00214639

ISSN：1880-6031

概要：　土砂を輸送してきた流れが透水性の高い平地上に流入すると，そこには扇状地にも似た堆積地形が形成される．本研究では，このような堆積地形の形成過程を数値的に再現することのできる解析モデルを構築することを目的とする．ここでは，地形の縦横断勾配の影響を合理的に考慮した掃流砂量の評価方法と，斜面崩落モデルとを組み込んだほか，表面流に加えて飽和・不飽和浸透流についても同時に解析することにした．この解析モデルの妥当性については，模型実験の結果とこれと同一条件下で行われた数値解析の結果とを比較することにより検討された．これにより，堆積地形の拡大が「流路の移動・消滅・再形成」のプロセスと密接に関わりながら進行することが確認されたほか，本解析によりこの過程が概ね合理的に再現できることも示された．

ISSN：2185-467X

概要：The purpose of this study is to understand the evolution process of river bed whose sediment size distribution is extremely wide. As a first stage of such study, movable bed experiments were conducted under the condition that the bed was composed of three different grain-sizes of sediment whose diameters take a different order of magnitude. One represents a group of larger size of sediment which can not move at all, and the others are in the group of medium or finer one which moves as a bed-load or a suspended load. In the process toward the stable state of bed, it was found that a typical vertical sorting occurred, and the characteristics of the bed structure were discussed on the basis of experimental results.

ISSN：2185-467X

概要：Erosion rate formula of cohesive sediment had been derived by the first author, but the there was very few information about it in the range that clay-content-ratio Rcc was less than 0.3. A series of erosion experiments were conducted in order to understand the effect of Rcc on the erosion rate. As a result, it was confirmed that the formula was valid in the range of Rcc between 0.1 and 1.0. The influence of watercontent-ratio on the test sample was discussed on the basis of experimental results. A deformation process and a stable profile of cohesive straight channel with a different value of Rcc were also investigated in order to understand the erosion process of cohesive sediment from a different point of view.

ISSN：2185-467X

概要：In order to understand the state of expected inundation in urban area due to a localized torrential rain, a numerical simulation technique can be extremely useful tool. The first author has kept conducting such a research work, and has developed his own technique. In this study, the effect of runoff process from a garden area in residential area to a road (and vice versa) was considered numerically, and the new submodel of it was added to the original model. And it was applied to the event which occured in the basin of the Myosyoji River in 2005. It was confirmed that the model works fairly well. As a result of this study, it was concluded that the effect of the above process was not negligible in this kind of simulation.

ISSN：2185-467X

概要：　東京などの大都市では，年に数回程度の頻度で設計規模を超える局地的集中豪雨に見舞われるようになった．このような豪雨時にはすでに存在している雨水排除システムがうまく機能するとは言えず，内水氾濫の発生が避けられない．この際に，最も大きな被害が懸念されるのが地下空間である．本研究では，浸水経験のある実在の地下空間を具体的な検討例として，そこで発生する浸水プロセスを明らかにすることを目指して数値解析手法を確立した．また，利用者のこの空間からの避難行動を数値的に解析する手法も考案した．さらに，この数値解析を通じて利用者の避難誘導をどのように行うべきかについて検討し，この空間から安全かつ円滑に避難誘導するための経路についても具体的に見いだしている．

ISSN：2185-467X

概要：In this study, series of experiments were conducted in order to investigate the effect of permeability of sediment on slope erosion by artificial rainfall. In this study, the slope was mainly composed of sand whose grain size was different in each case. In addition to such experiments, another investigation was carried out to find out the effect of adhesiveness on the erosion of slope which contains some amount of clay. As a result, it was found that overland flow affects surface erosion, and therefore the slope permeability governs the slope erosion considerably. And it was also confirmed that adhesiveness affects channel network formation due to the surface erosion considerably.

ISSN：2185-467X

概要：The purpose of this experiment is to understand the effect of sand transported from upstream reach of river on both deformation of bed with cohesive sediment and vertical bed structure. In this experiment, the amount of sediment feeding is equal to the amount of equilibrium bed-load transport, and experiment was continued until the deformation of the bed reaches the dynamic equilibrium state. As a result, characteristic vertical structure consisting of "sand layer", "sand-clay mixed layer" and "clay layer" were confirmed on the bed. In addition, it was seen that the existence of waves formed over the surface of cohesive sediment leads such vertical bed structure.

ISSN：2185-467X

概要：Recently, we often experience a localized torrential rain whose intensity is much larger than the design value for drainage network system. Numerical simulation ofinundation was conducted in order to estimate how hazardous the highly urbanized area of center of Tokyo is if such a heavy rain attacks there. There are several underground spaces including subway stations there, and a number of gates for stairs toward the space exist in the spots where the ground elevation is lower than the surrounding area. As a result of this study, it was concluded that serious inundation may occur in large scale underground space in this area. We also found out the gates leading to the space through which water flowing on road can enter.

ISSN：2185-467X

概要：　近年，東京都心部では想定を超える規模の集中豪雨に見舞われることが少なくない．本研究では，このような豪雨に見舞われたときに都心部の住宅密集地域ではどのような浸水が生じ，どのようなプロセスを経て内水氾濫が拡大するのかに注目し，これを数値解析により予測する手法を開発・確立することを目的とする．さらに，この手法を2005年に妙正寺川流域で生じた浸水・氾濫と，2008年に雑司ヶ谷地域で発生した下水道水難事故時の豪雨流出事例に適用した．結果として，現時点で得られているデータに限られるとはいえ解析手法の妥当性が検証されたほか，実際に被害にまで発展した浸水・氾濫のプロセスが水理学的にかなり精密に解析できるようになり，その理解も深まったと考える．

ISSN：2185-467X

概要：Fundamental process of surface erosion on bare slope which is caused by artificial rainfall was studied in this study. Numerical simulation was attempted under the same condition as the experiment that we conducted at the same time. Investigations were carried out for two type of the bare slope. Erosion process of the bare slope of sand which contains clay by 12% was one of the targets of this study. Numerical predictions technique was newly developed in consideration of being a non-equilibrium sediment transport process. Results of the numerical computation agreed well with experimental results, and the validity of the technique was confirmed.

ISSN：2185-467X

概要：Experimental investigations were conducted on the process of surface erosion and channel network formation on the bare slope. This is the process of sediment yields on the river basin. Some experiments were conducted to clarify the process of the erosion by varying both the gradient of slope and the width of mouth at the downstream end. It was found that characteristics of channels were different among the experiments, such as length, width, branches and interruptions. As a result, it became clear that the steepness of slope affects the length of the channel network in longitudinal direction. The width of the mouth, on the other hand, affected the width and the pattern of channel network in lateral direction.

ISSN：2185-467X

概要：The objective of this study is to clarify the deformation process of river bed which is composed of extremely wide range of sediment. The frame of bed is constituted by the larger rock or stone which cannot move at all. In this study, "the dynamic equilibrium state of river bed" was investigated experimentally. The flow discharge and the sediment discharge of supply were the parameters in experiment. The sand and gravel existing in a void of the stones of the large particle size is affected by the stones. It is called a hiding effect. It was found from this study that the riverbed reaches different dynamic equilibrium state according to a supplying rate of the sand or gravel, and the surface elevation of sand and gravel exposed on the riverbed surface changes.

ISSN：2185-467X

概要：In this study, inundation process in lowland areas of Tokyo which is bordered by the Ara River and the Sumida River was investigated numerically. Numerical technique developed by the first author was applied in order to estimate how hazardous the urban lowland area under two different conditions. The state of inundation which is caused by a localized torrential rain was predicted. Inundation rocess in this area was also investigated numerically under the assumption that the overflow from the Ara River into this area occurred. As a result of these simulations, the time series of information about the flow path of inundated water were obtained, and the aracteristics of inundation in this area were made clear.

ISSN：2185-467X

概要：Recently, the warming on the earth advances gradually. Under such circumstances, occurrence frequency of the torrential rain increases in Tokyo. The technique of numerical prediction of the inundation is an effective tool in order to reduce damage due to such a torrential rain in urban area. In this study, the numerical prediction was conducted by using the rain data of the X-band MP radar as the first step to realize a real-time inundation forecast at the time of the localized torrential rain occurrence. Inundation in Shinjuku area that was highly-urbanized was investigated in this study by using the actual rain data that was measured locally on August 26, 2011. It was suggested that an inundation forecast could be realized soon in future.

ISSN：2185-467X

概要：Recently extremely strong rain came to attack the urban areas of Tokyo. As a result, urban inundation came to be frequent. Because there are several underground spaces including subway stations in this highly urbanized area in Tokyo, appropriate measures must be taken beforehand. Numerical simulation is effective to reduce damage of the inundation. In this study, we applied numerical prediction technique developed by the first author to the Tokyo downtown area. Based on the result, the inundation risk of the actual large-scale underground was made clear.

ISSN：2185-467X

概要：The Kanda river basin is a highly-urbanized area located next to the Tokyo metropolitan area. In this area, most ground was paved, and high density drain network has been constructed under the ground. Because of such condition, rain water concentrates rapidly to the drainage pipe, and it flows into urban river system. In this study, numerical simulation was conducted to investigate a process of urban inundation in this basin by focusing on the interaction between river and drainage system. Two rain events, Suginami torrential rain in 2005 and heavy rain event on June, 29 in 2014, were paid attention in this study. In the latter case, the rain data by X-MP radar which was provided by MLIT was applied. As a result of this analysis, it was revealed where the points with higher inundation risk lay hidden in this basin.

ISSN：2185-467X

概要：Experimental investigation was conducted on the dynamic equilibrium state of bed which was composed of extremely wide range of sediment. A void of larger stones was filled with medium gravel which moves as bed load and finer sand which moves as suspended load. Experiment was conducted with supplying gravel and sand. The flow discharge and the sediment supply discharge of gravel were set as fixed value, and the sediment discharge of sand was changed. The layer of only gravel was exposed on the bed surface under the condition that the discharge of sand was small. On the other hand, if the supplying rate of sand was large, the layer which was composed of both gravel and sand was formed below the bed surface. It was verified that this results were not changed even if the flow rate and the discharge of gravel changed.

ISSN：2185-467X

概要：Erosion process of clay riverbed was investigated. The clay riverbed is eroded by the action of water flow. It is also eroded by moving sand and gravel. In this study, the influence of moving sand and gravel on erosion of the clay is investigated. This process is affected by the amount of sand and gravel transport in the river. Movable bed experiments were conducted under the several conditions of both the flow discharge and the rate of sediment supply. As a result, we found that the relationship between the erosion rate of the clay riverbed and the rate of supplied sand has extreme value. It was also found characteristic vertical structure under the bed surface.

概要：Typhoon No. 26 in 2013 attacked the Izu-Oshima Island with record heavy rainfall and caused a disaster resulting from landslides and mud flows. This extreme event is the motivation of our study on how we evaluate hazardous zones at risk of mud flows and how we design structural and non-structural measures accordingly. The present study describes sediment runout processes, mud flow control by means of a guide wall, and a method to evaluate topological conditions in which landslides and mud flows avalanche into unexpected areas. The landslides took place in the western slope of Izu-Oshima, which is only about 2500m wide. Analyses on phase shifting from solid to liquid as well as on mobility of the soil masses suggest that the soil masses released by the landslides transformed directly into mud flows, and that the mud flows developed in size through sediment erosion in their run-out processes. The predicted results by means of a numerical model based on depth-integrated governing equations of sediment-water mixture flow suggest that mud flows could be controlled well using a guide wall, which shows a high possibility of mud flow control using a storage structure with a guide wall. In addition, we propose a simple method to evaluate topological conditions to judge whether mud flows will enter unexpected areas, which will provide a key to identify hazardous zones including even those that have been missed out conventionally.

ISSN：2185-467X

概要：Evacuation movement of persons from an inundated underground space was investigated in this study. Numerical simulation was conducted under the two conditions; (1) the persons were guided to evacuate in a recommended manner or (2) they escaped through the nearest stairs without guide. Simulation was also conducted in order to make clear the effect of evacuation announcement. It was confirmed that the guide was effective to make an orderly and safe evacuation movement. And the announcement was also effective to make persons escape more rapidly to a ground level in case that it was made at just the right time. This kind of computation must be needed before we make a plan of the announcement.

ISSN：2185-467X

概要：The main purpose of this study is to understand the evolution process of river bed in case that the sediment size distribution is extremely wide. In this fundamental experimental study, the bed is composed of three groups of sediment, and one of the grain size is completely different from each other. One is L-particle which cannot move at all in the stream, and constitutes a bed frame. And M-particle or S-particle exists in the space surrounded by L-particles, and moves as bed load or suspended load, respectively. Hiding effect of L-particle on M and S-particles was evaluated, and the vertical structure of bed was also made clear in the evolution process toward a static equilibrium state. In addition to these, it was found that the arrangement of L-particle cannot affect the state of equilibrium state.

ISSN：2185-467X

概要：Recently, we often experience a localized torrential rain whose intensity is much larger than the design intensity for drainage network systerm. In such a case, severe damage of inundation is expected especially in urban area. In order to reduce the magnitude of damage, the information obtained by numerical simulation is so effective. Recently, the authors have started the attempt for a real-time forecast of inundation as well as the localized torrential rain. In this paper, two numerical prediction techniques in each field were summarized. Numerical simulation of inundation was newly attempted by using the observed mesh-data of rain, and the discussion about the results of prediction was also conducted.

ISBN：4-381-01590-8

ISBN：4-320-07416-5

国際会議口頭発表（招待・特別）開催地：岐阜

国内会議口頭発表（招待・特別）開催地：東京

国内会議口頭発表（招待・特別）開催地：東京

開催地：広島

開催地：広島

開催地：広島

開催地：広島

開催地：広島

開催地：広島

開催地：宮城

開催地：宮城

開催地：宮城

開催地：福岡

開催地：福岡

開催地：福岡

開催地：福岡

開催地：北海道

開催地：北海道

開催地：北海道

開催地：長野

開催地：愛媛

開催地：愛媛

開催地：愛媛

開催地：神奈川

開催地：愛知

開催地：愛知

開催地：愛知

開催地：愛知

開催地：高知

開催地：千葉

開催地：千葉

開催地：千葉

開催地：千葉

開催地：千葉

開催地：大阪

開催地：大阪

開催地：大阪

開催地：大阪

開催地：岡山

開催地：岡山

開催地：岡山

開催地：岡山

開催地：岡山

開催地：宮城

開催地：宮城

開催地：宮城

開催地：宮城

開催地：宮城

開催地：宮城

開催地：富山

開催地：福岡

開催地：福岡

開催地：福岡

開催地：福岡

開催地：福岡

開催地：福岡

開催地：福岡

開催地：北海道

開催地：北海道

開催地：北海道

開催地：北海道

開催地：北海道

開催地：北海道

開催地：北海道

開催地：北海道

開催地：鳥取

開催地：高松市

開催地：高松市

開催地：高松市

開催地：高松市

開催地：高松市

概要：環境水理学，河川工学特論A(大学院科目)のテキスト．

概要：水理学演習のテキストとするため，「水理学A」の講義内容に関わる例題を集録したもの．

概要：埼玉県行政課題研究会として標記のシンポジウムが開催された．これに先立ち半年間にわたり，「総合的な学習の時間」に関して行政職員ならびに小学校教員との懇談を続け，その成果を上記シンポジウムで公表した．

概要：都市型水害特集

概要：都市水害，地下浸水

概要：都市水害，雑司ヶ谷下水道事故

概要：都市水害，雑司ヶ谷下水道事故

概要：急増する都市水害

概要：都市水害