A5080153641- Hydrology and Sediment Transport Processes
- Hydrology and Watershed Management Studies
- Soil erosion and sediment transport
- Fish Ecology and Management Studies
- Flood Risk Assessment and Management
- Landslides and related hazards
- Freshwater macroinvertebrate diversity and ecology
- Hydraulic flow and structures
- Land Use and Ecosystem Services
- Energy, Environment, Agriculture Analysis
- Urban and spatial planning
- Cryospheric studies and observations
- Geotechnical and Geomechanical Engineering
- Financial Crisis of the 21st Century
- Geology and Paleoclimatology Research
- Water Resources and Management
- Soil and Water Nutrient Dynamics
- Water Systems and Optimization
- Civil and Geotechnical Engineering Research
- Flow Measurement and Analysis
- Geotechnical Engineering and Analysis
- Water Quality Monitoring Technologies
- Aeolian processes and effects
- Water resources management and optimization
- Marine and coastal ecosystems
National Graduate Institute for Policy Studies
2025
The University of Tokyo
2002-2022
This study examined how urban river restoration processes can cultivate a sense of ownership and contribute to community-engaged climate change adaptation, focusing on the case Okazaki City, Japan. The research employed qualitative approach, analyzing local documents interviewing ten key volunteers ONE RIVER , citizens’ group. demonstrated that activities began with utilizing area subsequently expanded encompass community-based including sustainably maintaining environment across entire...
• The impacts of climate and land-use changes on water sediment dynamics were assessed for a river basin in northern Japan. Severe depopulation is currently undergoing rural areas Climate change decreased both discharge SS loads due to an increase evapotranspiration. Land-use yield but accelerated channel erosion, resulting little suspended loads. Combined substantially decrease yield. Graphical Abstract
Several bridge piers were visited, and their scour hole was characterized into three zones: scour, transition, mound zones. The observed onsite sorting scouring patterns recreated through flume experiments with varying pier aspect ratio (1:1, 1:2, 1:4 1:6) sediment geometric standard deviation (σg). showed that maximum depth decreased non-uniformity; 52.7 mm, 20.2 16.6 mm are the respective of beds σg = 1.4, 2.5, 5.2. While has minimal effect on values, it noticeable effects shape asymmetry....
落差工の存在は周辺地形を変化させ,生物にプラス,マイナス両方の影響を及ぼす.この影響を理解すべく,複数箇所で落差工周辺の地形,流況を観測し,その特徴及び形成機構を解析した.まず,落差工はその周辺に早瀬,淵,平瀬を形成するものの,河床低下区間では淵が形成されないことを示した.また,落差工下流に淵がない場合,その下流の早瀬はアーマー化していた.一方,落差工上流の平瀬では,河道の湾曲に対応し,内岸側が堅い礫,外岸側は軟らかい砂利の河床になるという分級が生じていた.なお,淵では,垂直に落ち込む流れのため,流量が少ない時は表層のみ流れ,多い時は底層に強い流れを生じていた.この様に,落差工周辺の瀬-淵構造は,落差工の構造,河道線形,河道縦断形といった様々なスケールの因子に規定されることを示した.
セグメントM，セグメント1，セグメント2-2 の多数の場所で河床材料の粒度分布を調査し，平均年最大流量時の無次元掃流力τ＊と比較しつつその結果について分析した．セグメントMとセグメント2-2とでは代表粒径が全く異なるにも関わらず，各セグメントにおいて大きい粒径成分を含む地点に限れば，その粒度分布形状はかなり類似していた．この分布形状は標準偏差が1.2の対数正規分布とほぼ一致し，空隙率がかなり小さい粒度分布といえる．一方セグメント1でも代表粒径に関わらず粒度分布形状がかなり類似していたが，その分布の標準偏差は比較的小さく，これはセグメント1のτ＊が小さく河床材料が移動しにくいためと考えられる．以上から，粒度分布形状の特徴と，それが平均年最大流量時のτ＊によってある程度説明できることを明らかにした．
The objective of the study is to improve understanding relationships between multiple spatial scales and development micro-habitat as well its co-dependence with net-spinning caddisfly (Stenopsyche mamorada). In this study, two target riffles located in Asa River basin were investigated during spring 2006. Three major findings research that; 1. specie seems prefer substrate median diameters 3-13 cm because they need medium-sized gravel create their nests, 2. abundance loose surface layer...
河川物理環境の改善には，土砂動態の把握が不可欠である．そこで，早瀬内の微生息場が形成される過程を，土砂動態の観点から調べることとした． 解析では，空間スケールの階層性に注目し次の三段階の過程に注目した．まず，土砂供給量が砂州の発達度を決定し早瀬形状が決まる過程，次に早瀬形状が決まり，その内部の水深・流速分布や河床形状が決まる過程，さらに早瀬内部での水理環境が決まった結果，砂の動き方が決まり，多様な河床構造が形成される過程である． その結果，以下のことが明らかとなった．まず，早瀬形状は供給土砂量が多く発達した砂州から順に，狭窄型，縦長型，横長型となり，それぞれ特徴的な縦横断勾配，水理環境を有している．また，早瀬の河床表層に形成される浮き石は流量の大きな早瀬ほど厚く，形状的には狭窄型が最も多様で厚い浮き石が形成されやすい．さらに，早瀬内部の礫構造は，瀬脇よりも澪筋が，瀬頭よりも瀬尻が，厚い浮き石の層を形成しやすい．ただし砂の流入量は左右岸で異なり，洪水後しばらく砂が流れる瀬脇とそうでない瀬脇ができる．この様な浮き石の形成には数週間の時間を要し，早瀬内の多様な礫構造が徐々に形成されていく．
This study aims to clarify the formation process of sediment exchange layer in riverbed through field observation two rivers and flume experiment, discuss relationships between transportation system layer. Several devices for were installed Asa Syubuto river. As a result, observed thickness was larger than previous studies. The experiment conducted confirm forming layer, revealed that thick is formed due bed degradation discharge increasing period sedimentation decreasing period. mechanism...
Subsurface water flow in a gravel bar is closely related to the river environment and stream ecological system. In this study, we investigated characteristics of subsurface focusing on which has various heterogeneous effects, such as permeability porosity gravels, shapes, during normal stage. A network wells was established measure table elevations bars bed rivers Tokyo, Japan. Permeability layer were surveyed by considering relationship with "gravel ratio" new indicator. The characteristic...
In the Nakatsu river, after dam construction in 2001, due to decrease of flood discharge, river course has been fixed, and gravel bar covered with vegetation. This study clarified relationships between roughness revetment characteristics morphological structures from dry riverbed riffle-pool structures. At first, historical change is investigated. River width normal flow condition stable for direction concentration flow, mechanism through flume experiment. Secondary, field measurement, case...
To promote sustainable water resource management through collaboration among multiple stakeholders including managers, users, and residents, it is essential to understand place meanings that people attribute the environment. The environment performs various functions, flood control, supply, habitat provision, recreation for people, serving as an energy source, cycle in entire catchment. Therefore, important which territories or ranges of within a catchment find meaningful develop initiatives...
PHABSIM is one of the most famous methods to estimate condition fish habitat. Recently many researches are performed improve PHABSIM. In this study we derived criteria for habitat Japanese dace (Tribolodon hakonensis). At first, paid attention seasonal change dace's utilized a different area in each season, but local depth and velocity was approximately constant all year round. So clarified that neig hboring affects Next, evaluated effect morphological changes on habitat, flattening sand...
本研究では,粗粒有機物の堆積過程と堆積物の質の関係を解析した.まず,河岸突出部の背後での有機物の堆積過程を調査し,物体背後の巻き返しには底層付近を漂う有機物が堆積しやすいという特徴を見出した.次に,表層を流れてきた葉の堆積場と底層付近を流れてきた葉の堆積場の違いに注目し堆積場を分類した.そして,分類された各堆積場より有機物を採集し,樹種,重量,分解度,底生動物相を調べた結果,これらの状態が堆積場間で異なっていた.これらから,葉の沈みやすさによって堆積場が決まり,堆積した葉の種類と堆積場の物理環境の相互作用で底生昆虫相が決まり,底生昆虫相と堆積期間で葉の質が決まるという一連の機構をまとめた.さらに,堆積場の中でも堆積期間の異なる葉が分級しており,空間的に堆積物の質が異なることを指摘した.
In gravel bed rivers, shape of sediments has significant influence on the sediment transport. Sediment transport analysis was refined by extending movement characteristics different shapes sediments. At first, mean velocity "i" sized particle: "Vpi" analyzed for each Zingg's category "m" through laboratory experiments. experiments, 4 to 32 mm sampled in Oppegawa River were colored and used at flow conditions slope. Moreover, more than 300 particles Fourier get roughness compute effective...
過去の砂利採取や横断構造物の設置が河川構造に影響し,複断面化や樹林化を招いた機構の解明を目的とした.一般に勾配は洪水規模と礫径に対応するが,砂利採取で大礫が減少した多摩川では以前の河床である高水敷と低水路の安定勾配が異なり,下流端の堰から上流に向かい低水路幅が狭まると共に高水敷との比高差が大きくなる形状で複断面化していた.同様の形状は他河川でも見られ,堰高や区間長に環境が規定されていた.さらに,以前と現在の安定勾配の差が大きい多摩川の扇頂部付近では,堰直下から下流に向かい土丹層を削り込む低水路が形成され,一つ下流の堰直上からは上流に向かい礫の河道を形成する.この境界部では大礫が露出し,川幅や勾配の不連続点が存在した.以上の河道形成過程と現在の植生,特にハリエンジュの生育状況の関連性を示した.