事務所の取り組み
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首都圏外郭放水路
Overview of Facilities
Why were the Nakagawa, and Ayase River basins Repeatedly Devastated by Rain-related Flooding ?
Being surrounded by large rivers like the Tone, Edogawa and Arakawa Rivers, it has topography like a bowl that easily accumulate water.
A Bowl-like Ground Surface Tends to Accumulate Water
The Nakagawa River drainage basin had been devastated since early times due to its changed flow channel caused by flooding of the Tone and Arakawa Rivers. Being surrounded by large rivers like the Tone, Edogawa and Arakawa Rivers, it has topography like a bowl that easily accumulate water. And since the water level inclines gradually, the area remains in a dangerous state after heavy rains fall because water levels do not fall quickly.
Repeated Flood Damage
The low lying ground easily accumulates water. This area suffered flood damage many times because the river and sewage projects designed to prevent flood damage were not able to keep up with rapid urbanization. If urbanization continues, damage to this area will be incomparably greater than in the past.
"The Nakagawa and Avase Rivers' Comprehensive Flood Control Measures" for Developing a Town Less Vulnerable to Flood Damage
In order to protect the area from flood damage, it is necessary, in addition to improving flood control facilities being carried out so far, to restore the water-retaining and flood control functions the original river lost due to the development, through an integrated effort carried out in the area. We must develop such drainage basin measures to prevent rain water from running into and bursting rivers. "The Nakagawa and Ayase Rivers' Comprehensive Flood Control Measures" are aimed at making the town resistant to flood damage based on the integrated effort of everyone living in the drainage basin. The Metropolitan Outer Area Underground Discharge Channel is, in particular, expected to be the main pillar of the measures.