July 11, 2018, our class went to go visit Inokashira park zoo and the Kanda river / loop road no. 7 underground regulating reservoir, held by the Zenpukuji River Facility.
The underground regulating reservoir goes 50 meters underground and stretches for about 5 kilometers (3 miles), a tunnel that exists to store water for when the heavy rain comes and for when a possibility and risk for a flood to arise. Before the reservoir, Kanda river tended to overflow a lot, and in August 1993, there was a flood with the highest about 44 mm, where from about 1 pm it started to rise, and reached its peak around 3 pm. The river could no longer hold the water so the water begun to overflow onto the streets and on the roads that people normally use. This became a big issue, and so they then decided that in order to ensure safety in Tokyo, they need to widen the river channel so that the water can flow safely. Although the process itself did not seem easy to happen, where houses had to be moved, time was spent, and 540 thousand yen was spent to create the tunnel, it seemed to be completely worth it in creating this reservoir.
Seeing the way they had formed this tunnel so that when the water comes, they can open the water gate in the right timing so to balance the water level out, made the money they had spent it on seem like it was saving rather than spending. By making this tunnel, I am pretty sure they had already saved more lives than they could have without the tunnel existing. The tunnel itself was dark, mirky, and cold, but because it is there, Tokyo is now one of the safest places in Japan. Kanda river itself is also not appealing to by-passers, but to think about its function and the storage tunnel it has underneath makes me glad that it is there in the first place.
Human Ecology: Rivers 