In the midst of global climate change, a large typhoon has hit Japan and unprecedented heavy rainfall is occurring. In large cities in Japan, underground discharge channels and underground regulating reservoirs are being developed to improve the flood control safety.

In this paper, we confirm the flood reduction effect of these underground facilities against the rainfall generated by Typhoon Hagibis in the Tokyo area in 2019.

In addition, the advantages of underground regulating reservoirs in the metropolitan area are discussed from two aspects: cost and land acquisition. It is confirmed that the underground reservoir type has remarkable advantages in both aspects.

中文翻译：

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东京地区小城市河流的地下排放渠道/水库的影响

在全球气候变化之中，一场大型台风袭击了日本，并且正在发生前所未有的强降雨。在日本的大城市，正在开发地下泄洪通道和地下调节水库，以提高防洪安全。

在本文中，我们确认了这些地下设施对 2019 年东京地区台风海贝思产生的降雨的防洪效果。

此外，从成本和征地两个方面探讨了都市圈地下调节水库的优势。证实了地下水库类型在这两个方面都具有显着的优势。