Japan Water Agency Arakawa Dam Integrated Management and Construction Office

TAKIZAWA DAM and URAYAMA DAM 2006/10 Japan Water Agency Arakawa Dam Integrated Management and Construction Office

The Ara River System Basin Tochigi Pref. Ibaraki Pref. Nagano Pref. Takizawa Dam Futase Dam Takizawa Dam Arakawa dam office Urayama Dam Arima Dam Saitama Pref. Saitama Yamanashi Pref. Urayama Dam Akigase Intake Weir Arakawa No. 1 Regulating Reservoir Chiba Pref. Tokyo Metropolis Drainage basin of the Arakawa River System Flood inundation hazard area Takizawa Dam catchment area

Vertical Section of Major River in Japan and Ara River EL. Shinano River Ishikari River Altitud e Jyoganji River Ara River Tone River Urayama Dam Takizawa Dam Yorii Point Distance from Rivermouth 荒 川 自 然 P.329 坂 井 睦 郎 作 図 より

Specification of Takizawa Dam Normal water level Flood control level Total Lowest water reservoir level capacity 63 million m 3 Effective reservoir capacity 58 million m 3 Non-flood period (October 1 to June 30) Active capacity during non-flood period 58 million m 3 Unspecified-use active capacity 9 million m 3 Urban-use active capacity 49 million m 3 Power generation (58 million m 3 ) Sedimentation storage 5 million m 3 Flood period (July 1 to September 30) Flood control storage 33 million m 3 Active capacity during flood period 25 million m 3 Unspecified-use active capacity 4.5 million m 3 Urban-use active capacity 2.05 million m 3 Power generation (2.5 million m 3 ) Dam height 140 m Emergency spillway Standard spillway ight 140 m Dam he Energy dissipator Foundation bedrock Height 140 m (Concrete gravity dam) Crest Length 424 m Dam Volume 1.8 million m 3 Reservoir Capacity 63 million m 3

Specification of Urayama Dam Crest Normal water levell Dam height 156 m Standard spillway Crest length 372 m Crest length About 1.75 million m 3 Foundation bedrock Flood control storage: 23 million m 3 Flood control level Total reservoir capacity: 58 million m 3 Active capacity during flood period: 33 million m 3 Active capacity during non-flood period: 56 million m 3 Sedimentation storage: 2 million m 3 Lowest water level Height 156 m (Concrete gravity dam) Crest Length 372 m Dam Volume 1.75 million m 3 Reservoir Capacity 58 million m 3

Flood Control Plan for the Ara river System The flood control plan for the Ara River system aims to reduce the rate of discharge from 14,800 m 3 /sec., which is the figure at the Iwabuchi reference point where a flood will occur once every 200 years, 7,000 m 3 /sec. using the upstream dams, the Ara River control reservoirs and improving the course of the river. Takizawa Dam and Urayama Dam are playing an important part of the plan. Flood Control Plan for the Arakawa River System Nakatsu River Takizawa Dam Oohora River Futase Dam Urayama Dam River Ichino No. 4 and 5 Regulating Reservoirs Arakawa River River Iruma Iwabuchi No. 1, 2 and 3 Regulating Reservoirs Shingashi River Tokyo Bay Figures are design high water discharge Figures in the parentheses ( ) show dam regulation capacity Figures in the square brackets [ ] show basic high water discharge. Unit: m 3 /s

Flood Control Plan at Takizawa Dam inflow 1,850 m 3 /sec outflow 300 m 3 /sec Flood Control Plan at Takizawa Dam (constant rate discharging method) Design flood discharge Inflow to dam (Flow) Water stored in the dam reservoir Discharge from dam reservoir Design maximum discharge (time)

Flood Control Plan at Urayama Dam inflow 1,000 m 3 /sec outflow 110 m 3 /sec Flood Control Plan at Urayama Dam (natural regulation method) Flow Flow into dam reservoir Design flood discharge Water stored in the dam reservoir Flow after control Maximum discharge Photo showing flood Fcontrol operation Flood contro ol effect Qout = 100 m 3 /sec Flow discharged from dam Time

Ara River Flood 東 京 新 聞 (H13912 (H13.9.12 台 風 15 号 ) 埼 玉 新 聞 (H13912 (H13.9.12 台 風 15 号 ) Flood occurrence Aug. 1982 Sept. 1982 Description of damage Two deaths, 97 houses flooded above the floor level, 2,229 houses flooded below flood level One death, 4,163 houses flooded above the floor level, 13,005 houses flooded below flood level Peak flow at Yorii point (m 3 /s) Sept. 1991 2,750 houses flooded above the floor level, 9,335 houses flooded below flood level 1,948 Aug. 1993 410 houses flooded above the floor level, 2,902 houses flooded below flood level 2,054 Sept. 1998 674 houses flooded above the floor level, 3,925 houses flooded below flood level, 10 damaged river sites Aug. 1999 605 houses flooded above the floor level, 1,747 houses flooded below flood level 5,248 July 2000 517 houses flooded above the floor level, 997 houses flooded below flood level 1,712 Sept. 2001 3 houses flooded above the floor level, 23 houses flooded below flood level 3,888 The catchment area of the Arakawa River flowing through the Tokyo Metropolitan area, in which about one third the Japanese population and industries are concentrated, covers an area of 2,940 km 2 in the Tokyo and Saitama Prefectures, containing 19 wards, 39 cities, 24 towns and 7 villages, 9.2 million people with a population density of 3,100 people per km 2, and total assets of about 138 trillion yen. The assets in the area in the catchment area expected to be flooded total about 73 trillion yen. (Source: River Status Survey, March 1997) 5,450 3,790 2,950

Municipal Water Utilization Plan for the Ara Water System Arakawa River System Water Use Plan (for drinking water) Water available from Kakkaku Dam 1.0 Water available from Takizawa Dam 4.6 Yoshida River Nakatsu River rayama River Ur Water available from Urayama Dam 41 4.1 Yorii Arakawa River Water available from Arima Dam 0.7 Musashi Can nal Iruma River Akigase Intake Weir To Asaka Purification Plant and the amount of water taken in by Tokyo Metropolis 3.430 Tone Weir Sum mida Riv ver Water available from Arakawa No. 1 Regulating 3.5 Reservoir Arakawa Rive er To Okubo Purification Plant and the amount of water taken in by Saitama Prefecture Nakagawa River 9.776 Unit: m 3 /s Water made available from dams in the Arakawa River System (for drinking water) Takizawa Dam Urayama Dam Water made available Akigase Intake Weir Saitama Prefecture Tokyo Metropolis 4.6 3.680 0.860 4.1 2.696 1.170 Other Minano and Nagatoro 0.060060 Chichibu city 0.234 Kakkaku Dam 1.0 1.000 Arima Dam 0.7 0.300 Hanno city 0.400 Arakawa No. 1 Regulating g 3.5 2.100 1.400 Reservoir Total 13.9 9.776 3.430 0.694 Unit: m 3 /s

Arakawa River System The Ara River Drought Di Condition of the Arakawa Main River [near the Arakawa Bridge] (Aug. 20, 1996) (River water disappears.)

Water Supply District Minano Nagatoro Waterworks Corporate Group coverage area Nakatsu River Kakkaku Dam Takizawa Dam Futase Dam Urayama Dam Arima Dam Chichibu City Waterworks Department (Bessho and Hashidate Purification Plant coverage area) Saitama Pref. Tokyo Metropolis Bureau of Waterworks (Asaka Purification Plant coverage area) Saitama Prefecture Public Enterprise Bureau (Okubo Purification Plant coverage area) Arakawa River Akigase Intake Weir Tokyo Metropolis Area covered by each waterworks operator Area covered by water made available from Takizawa and Urayama Dams

Takizawa Dam Reservoir Legend National road Prefectural road Municipal road Service road for construction Detour road Eiti Existing road River Alternative prefectural road Alternative national road Alternative municipal road Quarry Construction earth dumping site Construction earth dumping site Forest reserve Construction earth dumping site Aggregate plant Concrete plant Diversion works Construction Road Plant road Forest reserve reserve Route 140 Approach road Forest reserve Former Route 140 Alternative municipal road Approach road Alternative municipal road Forest reserve Construction Road Detour road Right bank construction road

Progress of the Takizawa Dam Construction Project Seen from downstream of the dam (before work commencement) Seen from upstream of the dam (before work commencement) 1994 Seen from downstream of the dam Seen from upstream of the dam (during work) (during work) Aug. 2004

Progress of the Takizawa Dam Construction Project Photos taken in August 2004 Dam body Quarry Center of Takinosawa No. 4 alternative road bridge

Progress of the Takizawa Dam Construction Project Seen from upstream of the dam (before start of ponding) Ponding started (Oct. 2005) Sept. 2005 Oct. 2005 Seen from downstream of the dam (present condition) Seen from upstream of the dam (present condition) Sept. 2006

Former National Road Route 140 Takizawa Dam Futase Damu Former National Road Route 140

New National Road Route 140 New National Road Route 140 Takizawa Dam Futase Dam Former National Road Route 140

Progress of the Takizawa Dam Project Year Type of work Land compensation 1969 Start of the inve estigation for the executio n plan 1976 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 Transfer of the project Instruction on th he project policy Loss compensation settled in Dec. 1988 Instruction on th he change of the project po olicy (incorporation of power generation plan ) Establishment of the Arakawa Dam General Project Office Fishing loss compensation agreement settled in March 1992 Compensation for loss settled Transfer completed in Dec. 1996 in Nov. 1992 Public loss compensation agreement settled in Mar. 1997 body Con nstruction of dam road Alternative Temporary drainage channel Excavation Concrete casting, etc. Foundation work Discharge facility National road Prefectural road Municipal road Landslide protection work Construction started as a prefectural road in Dec. 1978 Agreement concluded in Dec. 1978 Construction of service road stared in Nov. 1973 Commencement in 1985 Commencement in Dec. 1997 Diversion started in April 1999 Commencement in May 1999 July 2001 Commencement (water intake) in Mar. 2002 Agreement concluded in March 1993 (status improved from prefectural road to national road) Opened to traffic in Oct. 1998 Agreement concluded in Jan. 1994 Scheduled completion of concrete casting in Oct. 2004 Oct. 2005 Opened to traffic in Mar. 2004 Scheduled opening to traffic in March 2008 Oct. 2005 Test ponding

Tourist Spots and Future Prospect of Otaki Village 彩 の 国 ふれあいの 森 遊 湯 館 Forest of the 21st Century Nakatsu Valley 中 津 渓 谷 Green School 三 峯 山 ロープウェイ Mt. Hakutai Takizawa Dam Mitsumineguchi Fishing ground Tochimoto area Lake Chichibu Camping site Hot spa Arakawa Village 秩 父 湖 Stalactite cave Ootaki Village Mitsumine Shrine Hiking course Legend Route 140 Major roads Karisaka Tunnel 三 峯 神 社 Mountaineering trail ループ 橋 Hiking trail Mountaineering trail

Cost Reduction Efforts The operators of the Takizawa Dam actively carry out the following measures to reduce the construction cost as follows: Reduce the excavation muck for construction of the dam body and make effective use of the muck as fill materials. Slope protection work Recycling as fill materials Muck generated from excavation of the dam body is put to effective use as the protective fill material. Cost reduction is achieved by using low-quality materials as Fill aggregate for dam concrete. Muck generated from excavation of the tunnel is put to effective use as aggregate for dam concrete. CSG fill Excavation slope is made softer to reduce the amount of slope River bed Unitized revetment work protection. Conduit work: pressure-resistant polyethylene ribbed pipe Felled trees and roots are incinerated at charcoal burners to turn them into charcoal Standard products. section view of the protection embankment Effective value engineering disposals are adopted for erection in bridge construction.

Cost Reduction Efforts Active Use of Low-quality Aggregate Helps Reduce Construction Cost Waste rock Reduction in the amount of earth to be discarded Waste rock Rock recycled as dam concrete aggregate Excavation base Excavation base Rock recycled as dam concrete aggregate Rise in the excavation base (reduction in the amount of quarry to be excavated) Quality High quality Low quality Rock class CH class CM class CL class Conventional approach Excavate Excavate Dispose Dispose Dispose This project Excavate Excavate Excavate Excavate Dispose Excavation and selection of rock at the quarry

Ongoing Investigation of Raptor Habitat The basic idea about environmental preservation with respect to construction of the Takizawa Dam is minimization of the impact on the environment. Coexistence with the natural environment is another important factor for the dam. Investigation is ongoing for the habitat of fauna and flora in the area to be ponded and its neighboring area. Ecological Survey of Raptors The habitat investigation of raptors, including the Hodgson's hawk eagle, has been conducted since 1996. Investigation, including analysis, is based on the state-of-the-art knowledge with the assistance of specialists, and appropriate preservation measures are being taken based on the investigation results under the directions of the specialists. When any falcon is confirmed to be breeding, appropriate preservation measures are taken, including suspension of construction of an alternative road as required. Hodgson's hawk eagle: March to June 1997 Goshawk: April to July 2000 May to July 2001 Hodgson's hawk eagle: February 2002 to Mainichi Shimbun, dated Feb. 23, 2002 Young goshawk about to leave the nest

Environmental Preservation Efforts The Takizawa Dam operators transplant ferns and trees that grow in the construction area to preserve the ecological harmony of the neighborhood of the dam site as part of their efforts to preserve the environment. They also pick up seeds of plants growing in the reservoir area and grow and plant them around the dam reservoir. On April 26, 2003, the Development of the Green Hometown event was held, in which some 300 elementary school students from around Chichibu city collected seeds of trees that grew in the reservoir area (Japanese mallotus, zelkova tree, aralia elata, carpinus tschonoskii, and meliosma myriantha) and planted them in the neighborhood in a cooperative manner with the help of two NPOs, Arakawa Gakusha Chichibu and Morino-Kyoryoku.

Management Services of the Urayama Dam Meteorological satellite Radar rainfall meter Meteorological Water Resources Development Arakawa-Joryu River information provider Public Corporation Management Office, Ministry of Land, Infrastructure and Transport Facility management includes: management of dams and their associate facilities and equipment regular maintenance of dam facilities patrolling the dam reservoir area investigation of water quality of reservoirs and the natural environment around the dams Verification and management of data Facility management Service to inspect dams and their associated facilities and equipment so that they can always perform their intended functions High-water management Collection of data on meteorology, water level, etc. and prediction of flood based on the collected data Inspection of discharge facilities Notification to the relevant organizations and warning to and patrol in the downstream areas Start of discharge Flood control Completion of flood control Low-water management Administration, police and fire department Collection of data on downstream rivers, such as meteorology and flow. Determination of the amount of water to supply Operation of supply Low-water management Making an effective use of water stored in the dam reservoir depending on the purpose. Coordination with the facilities for the Arakawa River System to ensure effective use of valuable water is necessary. Operation room of the Urayama Dam Operation room High-water management Collection of data on typhoons and heavy rainfall and control of flood based on the gathered data Warning station Patrol boat Warning vehicle Dam values Rainfall observation station Water level observation station CCV camera

Operation Records of the Urayama Dam As of 0:00, Reservoir level (EL.m) 400 Normal w ater level EL.393.3m Sept. 29, 2006 Rainfall (mm) 1000 390 900 380 800 370 14 Rainfall 年 月 in 雨 2002 量 15 Rainfall 年 月 in 雨 2003 量 16 年 月 雨 量 360 17 年 月 雨 量 Rainfall in 2004 Rainfall in 2005 18 Rainfall 年 月 in 雨 2006 量 2002 平 成 14 年 350 平 2003 成 15 年 平 2004 成 16 年 平 2005 成 17 年 340 平 2006 成 18 年 Limited w ater level EL.372.0m 700 600 500 400 330 300 320 200 310 Low est w ater level EL.304.0m 100 300 0 January February March April May June July August September October November December 1 月 2 月 3 月 4 月 5 月 6 月 7 月 8 月 9 月 10 月 11 月 12 月 * The rainfall in September 2006 is the cumulative amount up to the 28th of September.

Problems of the Urayama Dam 1. Lengthening of Water Turbidity Period The water of the reservoir tends to stay turbid for a long time after the occurrence of a large flood. As the water turbidity period lengthens, various problems occur, such as the difficulty of downstream water users to take water and the worsening quality of the river environment. After floo od e flood Before

Problems of the Urayama Dam 2.Use of the Former Quarry Site and Protection ti of Birds of Prey Use of the former quarry site (Natureland Urayama) and protection of the Hodgson's Use of the former quarry site (Natureland Urayama) and protection of the Hodgson s hawk eagle, which lives in the neighborhood

Urayama Dam Accessible for the Local Community Dam Right Bank Plaza and the Reference Library

Development of the area around the reservoir Urayama Dam Accessible for the Local Community Construction of lakeside parks Use of canoes Building of recreation trails

Urayama Dam Accessible for the Local Community Chichibu Cherry Blossom Lake Festival Prince Chichibu Memorial Road Race Upstream and Downstream Exchange Meeting 時 期 イベント 等 名 備 考 8 月 秩 父 さくら 湖 まつり 主 催 : 荒 川 ダム 総 合 事 業 所 第 一 日 曜 日 11 月 下 旬 秩 父 宮 記 念 ロードレース 大 会 主 催 : 秩 父 市 ほか 後 援 : 荒 川 ダム 総 合 事 業 所 2 月 中 旬 秩 父 さくら 湖 駅 伝 大 会 主 催 : 秩 父 市 サッカースポーツ 少 年 団 後 援 : 荒 川 ダム 総 合 事 業 所