Focusing on green infrastructure (GI), which utilizes nature’s diverse resources, we developed urban flood control measures on three small-scale private tracts in Tokyo and Fukuoka in Japan, experiencing high rainfall. In addition, we implemented these measures and verified the possibility of introduction. Using a target rainfall of 100 mm/h and previous rainfall data, we set our goal of reducing runoff from each site below the capacity of a public sewage pipe. Implementation was conducted by assessing the soil infiltration rate and developing and installing rain gardens and storage layers using crushed stones. These measures satisfied the initially set goals, drastically reducing runoff at all three sites. The target installation cost was set at 100,000 yen per cubic meter of runoff reduction. The target costs were met in the two Fukuoka sites but not at the Tokyo site. The key reasons were the high costs of removing non-permeable surfaces or improving the soil of compacted surfaces, which called for a process to balance the runoff reduction and cost to determine the most effective plan for implementing GI in urban areas. The development and implementation processes were conducted in collaboration with the house owners and concerned parties; the workshops produced constructive ideas being unconstrained by conventional thinking. Visitors highly appreciated ideas related to using water because the techniques were derived from the Japanese culture of lifestyle. Thus, introducing attractive and effective GI may be possible through collaboration. Additionally, sharing experiences led to the formation of new community ties, supporting post-implementation site maintenance.

1. [1] J. Teramura and Y. Shimatani, “Quantifying disaster casualties centered on flooding in the Chikugo River middle basin in the past 400 years to determine the historical context of the July 2017 northern Kyushu torrential rainfall,” J. Disaster Res., Vol.14, No.8, pp. 1014-1023, doi: 10.20965/jdr.2019.p1014, 2019.
2. [2] World Meteorological Organization and Global Water Partnership, “Urban flood risk management – A tool for integrated flood management,” Associated Programme on Flood Management, 2008.
3. [3] American Rivers, Association of State and Interstate Water Pollution Control Administrators, National Association of Clean Water Agencies, Natural Resources Defense Council, The Low Impact Development Center, and U.S. Environmental Protection Agency, “Managing wet weather with green infrastructure – Action strategy,” 2008.
4. [4] United States Environmental Protection Agency (USEPA), “What is green infrastructure?,” https://www.epa.gov/green-infrastructure/what-green-infrastructure [accessed August 26, 2020]
5. [5] NYC Environmental Protection, “NYC Green Infrastructure Plan, A sustainable strategy for clean waterways,” 2012.
6. [6] Ministry of Land, Infrastructure, Transport and Tourism, “About the current state of comprehensive flood control measures,” https://www.mlit.go.jp/river/shinngikai_blog/past_shinngikai/gaiyou/seisaku/sougouchisui/pdf/2_1haikei_keii.pdf (in Japanese) [accessed September 16, 2020]
7. [7] M. Imbe and H. Okui, “The role, situation of spread and future perspective on rainwater storage and infiltration facilities,” J. of Japan Society of Water Policy and Integrated River Basin Management, Vol.2, No.1, pp. 5-14, 2013 (in Japanese).
8. [8] Ministry of Land, Infrastructure, Transport and Tourism, “National Spatial Strategy,” 2020 (in Japanese).
9. [9] Ministry of Land, Infrastructure, Transport and Tourism, “Climate change adaptaion plan of Ministry of Land, Infrastructure, Transport and Tourism,” 2018 (in Japanese).
10. [10] Y. Ogahara, F. Taura, and Y. Shimatani, “Flood and CSO suspression effect by green infrastructure targeting upstrean Zempukuji River basin,” The J. of Japan Society of Civil Engineers Ser B1 (Hydraulic Engineering), Vol.74, No.5, pp. 355-360, doi: 10.2208/jscejhe.74.5_I_355, 2018 (in Japanese).
11. [11] J. Kim, “Exploring green infrastructure benefits at house and neighborhood scale: case study of Illinois, USA,” Landscape and Ecological Engineering, Vol.14, pp. 165-174, doi: 10.1007/s11355-017-0331-0, 2018.
12. [12] N. Furuta and Y. Shimatani, “Integrating ecological perspectives into engineering practices – Perspectives and lessons from Japan,” Int. J. of Disaster Risk Reduction, Vol.32, pp. 87-94, doi: 10.1016/j.ijdrr.2017.12.003, 2018.
13. [13] N. Barclay and L. Klotz, “Role of community participation for green stormwater infrastructure development,” J. of Environmental Management, Vol.251, doi: 10.1016/j.jenvman.2019.109620, 2019.
14. [14] J. Lamond and G. Everett, “Sustainable blue-green infrastructure: a social practice approach to understanding community preferences and stewardship,” Landscape and Urban Planning, Vol.191, doi: 10.1016/j.landurbplan.2019.103639, 2019.
15. [15] F. Taura et al., “Design and practices towards to “Rainwater Society” that de-centralied water management for sustainable well-being society,” The J. of Japan Society of Civil Engineers D3, Vol.75, No.5, pp. 153-168, doi: 10.2208/jscejipm.75.I_153, 2019 (in Japanese).
16. [16] S. Yamashita et al., “Smart adaptation activities and measures against urban flood,” Sustainable Cities and Society, Vol.27, pp. 175-184, doi:10.1016/j.scs.2016.06.027, 2016.
17. [17] S. Yamashita, R. Watanabe, and Y. Shimatani, “Smart adaptation to flooding in urban areas,” Procedia Engineering, Vol.118, pp. 1096-1103, doi:10.1016/j.proeng.2015.08.449, 2015.
18. [18] The Architectural Institute of Japan, “Architectural Institute of Japan environmental standards, technical standards for rainwater harvesting,” AIJES-W0003-2016, 2016 (in Japanese).
19. [19] Y. Shimatani, “Strategic Bacic research programs, research and development implementation completion report –Distributed Rainwater Management for a Sustainable Well-being Society–,” RISTEX, 2020 (in Japanese).
20. [20] R. Itsukushima et al., “Study of outflow control effect of on-site storage and soil improvement for small watershed,” The J. of Japan Society of Civil Engineers B1, Vol.72, No.2, pp. 49-58, doi: 10.2208/jscejhe.72.49, 2016 (in Japanese).
21. [21] A. Iida et al., “A simulation study of rainwater infiltration and flood prevention effects by urban green spaces in Kanda River, Tokyo,” J. of the City Planning Institute of Japan, Vol.50, No.3, pp. 501-508, doi: 10.11361/journalcpij.50.501, 2015 (in Japanese).
22. [22] Road and Sewerage Bureau, Fukuoka City Government, “Stormwater management Do-plan 2026,” 2019 (in Japanese).
23. [23] M. Ohme, F. Taura, T. Moriyama, and Y. Shimatani, “Development of runoff controlled rain gardens and a study of its effectiveness,” The J. of Japan Society of Civil Engineers Ser B1 (Hydraulic Engineering), Vol.76, No.2, pp. 799-804, 2020 (in Japanese).
24. [24] Tokyo Metropolitan Government Comprehensive Flood Control Measure Council, “Tokyo metropolitan government rainwater storage and infiltration facilities technical manual,” 2009 (in Japanese).
25. [25] Tokyo Metropolitan Government, “Tokyo metropolitan government stormwater control measure basic policy (revised edition),” 2014 (in Japanese).