Comprehensive Flood Control Measures in the Tsurumi River Basin in Japan

ABSTRACT

With its 42.5-km-long main channel and catchment area of 235 km². the Tsurumi may be a small river even in Japan, but it flows through the central part of the Tokyo Metropolitan Area. The percentage of urbanized areas in the basin, which had been only 20 per cent 30 to 40 years ago, has increased to 80 per cent. The change of land use increased the flood runoff and necessitated the repeated revision of the channel improvement plan. Without nonstructural measures like onsite storage of rainwater traditional structural measures like river channel improvement works cannot save the basin from habitual flooding. The Ministry of Construction and the local municipalities responsible for river improvement, sewerage, and regional development established the Tsurumi River Basin Comprehensive Flood Control Council in 1980. Efforts are being made to maintain the retention and detention functions of the river basin and encourage land uses compatible with the conditions of flood control structures.