Location

Kyoto, Japan

Kyoto is the old capital city of Japan and is a central tourist destination at present. Kyoto is surrounded by mountains, and has climatic conditions with extreme temperature differences, hot in summer and cold in winter. While modernization is happening, the city preserves its historical landscapes, and local people actively utilize traditional knowledge in their daily lives.

 

Issue

Urban floods and extreme temperature

In recent years, there are growing concerns about the heat island phenomenon and flood damage caused by torrential rains in the City. In urban areas, temperatures remain high throughout the day and night due to air heating from heated concrete asphalt and other materials and exhaust heat from buildings. In addition, it is becoming increasingly common in recent years for heavy rains to exceed the capacity of sewage systems to discharge water into rivers, causing flooding and other damage in many areas.

 

Solution / Lesson learned

Use of rain gardens for stormwater management in urban design and planning

A rain garden is kind of a green infrastructure with a structure that allows rainwater that falls on the ground to slowly percolate into the ground, rather than being discharged directly into the sewage system. In urban spaces covered with asphalt and other materials, rain that falls on the ground drains away without being soaked into the ground. Rain gardens contribute to a healthy water cycle by temporarily storing rainwater that overflows onto the streets, thereby reducing flooding and recharging groundwater. Furthermore, rain gardens have a design aspect and can be enjoyed as a familiar garden in the city. In addition to mitigation of the heat island effect and controlling rainwater runoff, rain gardens are expected to have a variety of other benefits such as urban greening and water purification. In Kyoto, beautiful gardens incorporating rain garden functions have been created at temples and shrines since ancient times. Kyoto is taking advantage of its traditional culture and technological capabilities to promote the development of rain gardens, especially on roads and other public land.