Continuing urbanization has reduced permeable land areas, causing rainwater runoff volumes to rise, which not only increases the drainage burden placed on rivers and sewerage system, but also increases flood damage risk with the increases in torrential rains brought about by climate change. As physical flood control infrastructure has high costs and requires long planning and construction times, more effective utilization of existing infrastructure is required in addition to new construction. Moreover, as urbanization continues, the use of privately owned land for flood control as well as the limited publicly owned land available is increasingly important. This article reports the results and efficacy of a project to create a rainwater management network by connecting multiple pumping stations with the city’s main rainwater pipeline in coordination with river development in a major river drainage basin region, while rebuilding aging pumping stations for continued use, as well as the effectiveness of rainwater storage facilities in underground locations beneath privately owned buildings.

1. [1] Intergovernmental Panel on Climate Change (IPCC), “Fifth Assessment Report,” 2013.
2. [2] Japan Meteorological Agency, “Global Climate Change Prediction Information Volume 9,” 2017 (in Japanese).
3. [3] H. Tsuguti, N. Seino, H. Kawase, Y. Imada, T. Nakaegawa, and I. Takayabu, “Meteorological Overview and Mesoscale Characteristics of the Heavy Rain Event of July 2018 in Japan,” Landslides, Vol.16, Issue 2, pp. 363-371, 2019.
4. [4] H. Tsuji, C. Yokoyama, and Y. N. Takayabu, “Contrasting Features of the July 2018 Heavy Rainfall Event and the 2017 Northern Kyushu Rainfall Event in Japan,” J. of the Meteorological Society of Japan, Ser. II, Vol.98, Issue 4, pp. 859-876, 2020.
5. [5] Q. Zhou, G. Leng, J. Su, and Y. Ren, “Comparison of Urbanization and Climate Change Impacts on Urban Flood Volumes: Importance of Urban Planning and Drainage Adaptation,” Science of the Total Environment, Vol.658, pp. 24-33, 2019.
6. [6] U. A. Ngamalieu-Nengoue, F. J. Martínez-Solano, P. L. Iglesias-Rey, and D. Mora-Meliá, “Multi-Objective Optimization for Urban Drainage or Sewer Networks Rehabilitation Through Pipes Substitution and Storage Tanks Installation,” Water, Vol.11, Issue 5, Article No.935, 2019.
7. [7] Ministry of Land, Infrastructure, Transport and Tourism, “Project effect: Tsurumi River system, Tsurumi River multipurpose retarding basin, etc.,” 2016, http://www.mlit.go.jp/river/kouka/jirei/pdf/063.pdf (in Japanese) [accessed November 4, 2020].
8. [8] S. Fukuoka, T. Kon, and S. Okamura, “Assesment of Flood Control Effects of the Tsurumigawa River Multi-Purpose Retarding Basin,” Doboku Gakkai Ronbunshuu B, Vol.63, No.3, pp. 238-248, 2007 (in Japanese).
9. [9] A. Mailhot and S. Duchesne, “Design Criteria of Urban Drainage Infrastructures Under Climate Change,” J. of Water Resources Planning and Management, Vol.136, No.2, pp. 201-208, 2010.
10. [10] N. Koyama and T. Yamada, “A Proposed Simultaneous Calculation Method for Flood by River Water, Inland Flood, and Storm Surge at Tidal Rivers of Metropolitan Cities: A Case Study of Katabira River in Japan,” Water, Vol.12, No.6, Article No.1769, 2020.