River Basin Management in Japan Hitomi Godou
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River Basin Management in Japan -Flood Control Measures, Water Resources Management- Hitomi Godou Director of River Information Office, River Bureau Ministry of Land, Infrastructure, Transport and Tourism Contents • Flood Control Measures – Related Laws • River Law • Law on Measures against Inundation Damages in Designated Urban Rivers – Examples of River Basin Management (Tsurumi River) – Non-structural measures • Collection and Provision of River Information • Water Resources Management – Related Laws • Water Resources Development Law Non-structural measures – Recent trend of water resources • Climate Change • Integrated Water Resource Management History of the River Act 1896 1964 1997 Establishment of integrated Birth of modern river Establishment of systems for systematic flood river management system for management system flood management, water management and water utilization and environmental utilization conservation ・ ・ Improvement and conservation of river Introduction of integrated environment management system for river ・ Introduction of a system for river systems planning reflecting the opinions of local ・ Establishment of water community utilization rules and regulations Flood management Water utilization Flood management Flood management+ Water utilization Environment Transition from the old system to the new system due to the River Law amendment Content: basic policy; design flood; River works River river works river design flood discharge, etc.; major river work items Master plan for Drafting of master plan for river works Old system River Council Opinion (Class A river systems) Adoption of master plan for river works plan Content: basic policy, design flood, Content: goal of river improvement, river works, improvement design flood discharge, etc. scope of river maintenance River works, River River improvement improvement River Basic policy for river Basic policy for river river maintenance river Draft Opinion Academic experts Drafting of basic policy Infrastructure for river improvement Development Council Reflecting public opinions (Class A river systems) Opinion by, for example, New system Prefectural river councils Adoption of draft river holding public hearings Opinion (Class B river systems) improvement plan Adoption and announcement of basic policy Head of local government for river improvement Opinion Only if there is a prefectural Adoption and announcement river council of river improvement plan System of Comprehensive Flood Control Measures zConstruction of dams, retarding basins, River Administrator ①River Measures and discharge channels (National Gov’t, Prefectures, zRiver improvement (embanking, dredging) Municipalities) zPreservation of urbanization control are Comprehensive Flood Control Measures Control Flood Comprehensive zPreservation of natural lands Water zConstruction of food control ponds retaining area zConstruction of rainwater storage zConstruction of permeable pavements and rainwater infiltration inlets Local Government (Prefectures, zPreservation of urbanization control areas ②Basin Measures Water municipalities) zRestriction on constructing mound retarding area zImprovement of farm management zDevelopment of facilities draining water into rivers Lowland area zConstruction of storage zPromotion of flood resistant buildings zEstablishment of warning and evacuation systems River zReinforcement of flood control system ③Damage Reduction Administrator zAnnouncement of inundation records and flood Measures hazard areas Local Government zPromotion of flood resistant buildings zPR to local residents 4 Outline of Law on Measures against Inundation Damages in Designated Urban Rivers against flood Structural measures Non-structural measures from rivers Measures River Law Flood Control Law (Prevention of flood) (Countermeasures against flood when it occurs) Law on Measures against Inundation Damages in Designated Urban Rivers around rivers Because previous each law has limited enforcement, this law strengthens against flood Measures countermeasures and assures flood control in river basin. Sewage Law City Planning Law ○Designate urban river (basin) ・Urban area covers more than 50% of river basin ・Average annual damage (occurred or predicted) exceeds 1 billion yen (=$10mil) ・Because of urbanization, it is difficult to control flood by constructing river facilities or flood control dams ○Formulate river basin flood control plan ・4 members (river and sewage administrators, governors, and mayors) make the plan together ○Implementation of measures 7 Outline of Tsurumi River (Geography) River basin area 235km2 Hill / tableland 70% Tokyo Chiba Pref. Main stream length 42.5km Alluvial lowland 30% Kanagawa Tsurumi river basin Pref. Riverbed gradient : 1/250 Tsurumi River Tsurumi River elevation Hayase- Tsurumi Onda River River River 0~20m Toriyama River Riverbed gradient :1/1,000 Outline of Tsurumi River (Urbanization and population increase) Urbanization ration has increased Rapid economic growth has turned natural area into urban area by 75% in 50years 1958 10% 1958 10 1966 20% Typhoon Karinogawa in Sep 1958 450,000 700,000 1975 60% Present 85% Typhoon No.17 in Sep 1976 1,200,000 1,880,000 Natural Area Urbanization Urbanization Population Urban Area OutlineOutline ofof TsurumiTsurumi RiverRiver (Effect(Effect ofof urbanization)urbanization) ・Population increased by Function of keeping and retarding water became weakened 1.4 million in 50 years ・85% of river basin area urbanized ・Typical urban river Before development After development AsAs aa resultresult Slight urbanization Significant urbanization 1,300 m3/s Peak runoff Volume Doubles ・Discharge into river Difference 770 m3/s has become faster Present Runoff reaches ・Peak runoff has Before its peak in becomes bigger Development 1/3 of time 2~3 hours 10 hours River related projects in Tsurumi River Basin inundation control plan Future flood control Existing retarding basin 【Administrator】 MLIT Tokyo Metropolitan Kanagawa Prefecture Yokohama City Tsurumi River multi-purpose runoff retardation area : International Tsurumi River multi-purpose runoff retardation area Stadium Yokohama Tsurumi River levee Overflow-type Drainage gate of runoff retardation area T s u r K u ara m suy i ama R Riv iv er e r Specifications for the Tsurumi River multi- purpose runoff retardation area -Service started: June 15, 2003 -Area: 84 ha -Total reservoir capacity: 3.9 million m3 -Floodwater regulation (Temporary channel) Runoff retardation area collects 200 m3/sec. (Planned river channel) Runoff retardation area and floodway collect 700 m3/sec. Sewerage projects in Tsurumi River Basin inundation control plan Natural drainage area Pump drainage area (Name) Rainwater storage tube (Name) RainwaterRainwater storagestorage facilitiesfacilities Development of facilities for target rainfall Planned discharge in pump drainage areas Planned storage of major facilities City Discharge Planned City Storage facility Planned area discharge Storage Yokohama Tsuzuki 17m3/s Yokohama Shin hasue trunk line 410,000m3 3 Kouhoku 142m /s Kozukue chiwaka trunk line 256,000m3 3 Hokubu 189m /s Kawasaki Shibukawa rainwater storage 144,000m3 Kawasaki Kase 55m3/s tube Egawa rainwater storage tube 81,000m3 Total 402m3/s Pump facilities Rainwater storage tube Present status and problems -Present status of River Basin Management (Present status of flood control reservoir)- Tsurumi river was designated as the first Comprehensive Flood Control River in 1979 to cape with rapid urbanization of river basin ● Flood retarding pond As a Result About 3,300 facilities Total volume 270 million m3 But more retarding ponds are necessary Storage,Storage, infiltrationinfiltration andand forestforest conservationconservation Development of rainwater storage and infiltration facilities, conservation of forested areas (Total effect by municipalities : 0.3 million m3) Storage Storage facilities in schools, Infiltration Infiltration by permeable pavement parks and public houses Infiltration Inlet Infiltration trench Forest Conservation Infiltration Inlet Infiltration trench ◆Purchase and conservation of forest in developing area Measures against inundation damage -Improvement of collecting and providing river information - Providing necessary information, quick emergency response and minimizing damages in case of flood. Providing information to the public ■Collecting Information ▼Home Page ▼Mobile Phone ▼Information Board Gauging station Monitoring Rain-gauge station camera Gauging station Patrol Monitoring camera River Management Office (MLIT) Flood Fighting Activity Evacuation facility Municipal Evacuation call Office Providing Information Evacuation call Water level and Rainfall observation by Telemeter ProvidingProviding WaterWater levellevel andand RainfallRainfall collectedcollected of of byby TelemeterTelemeter Rain gauge station multiplex radio transmission station Branch office Water gage station River information provider system Information provided by the Internet and Mobile phone Location of rainfall observation radar 2626 radar radar stations stations collect, collect, anal analyzeyze and and provide provide rainfall rainfall data data nat nationwideionwide Mt. Hako Mt. Pinshineri Mt. Muri Mt. otobe Mt. Yae Mt. Nishi Mt. Monomi Mt. Shirataka Mt. Yakushi Hijiri Plateau Mt. Houdatsu Mt. Takasuzu Mt. Akagi Mt. Fuka Mt. Mitsutoge Mt. Ohwa Mt. Gozaisyo Mt. Rakan Mt. Oogusu MT. Takagi Mt. Shaka Mt. Mt. Jyatoge Mt. Myojin Mt. Johgamori Happongi Mt. Kunimi ▲・・・Weather radar installed by River Bureau Rainfall Radar