Rainwater infiltration

In Yokohama City, the water circulation system has changed drastically due to the progress of urbanization, such as an increase in rainwater infiltration function, an increase in rainwater runoff, and good waterside loss. In such a situation, it is necessary to improve the rainwater infiltration function, reduce inundation damage, and effectively work on restoring a healthy water cycle.

Rainwater infiltration is one of the measures to restore the water cycle, and is widely installed nationwide.

Rainwater penetration masu has holes in the bottom and wall, unlike ordinary rainwater masu. Surround the bottom and surroundings of the masu with crushed stone to prevent the soil from touching it.

By installing rainwater infiltration masu, rainwater can be easily penetrated into the ground.

As a part of the collected rain penetrates into the ground, all rainwater does not flow into the river at once, and the infiltrated rain slowly reaches the river as groundwater or spring water. This reduces inundation damage, helps to grow trees, and helps restore rich nature.

In Yokohama City, rainwater infiltration masu is effective, and rainwater infiltration facility installation standards have been established so that infiltration water does not affect nearby buildings and retaining walls, and rainwater infiltration masu is set according to this. Is to be installed. In this, it explains the structure of the masu, separation from buildings and retaining walls, soil conditions to be considered and groundwater level conditions, and also explains how to use the infiltration facility setting judgment map.
Rainwater infiltration facility setting standard (PDF: 1,375KB) [applicable from April 1, 2018]

We divide city area into area to promote rainwater penetration and area to regulate and color and have you use for setting examination of rainwater penetration masu. From April 1, 2011, the penetration facility setting judgment map becomes a division of 6 colors to 2 colors, making it easier to see.

[Actual map overlaps with the basic survey data for urban planning in Yokohama City (land use status and building use status)]

Utilization of infiltration facility setting judgment map
http://translate-en.city.yokohama.lg.jp/kankyo/chisui/shintoumasu/map.html

You can see the infiltration facility setting judgment map in Public Works Office and Environmental Planning Bureau Sewer Management Division in each ward. The map for April 2011 can also be viewed from the administrative map information "Daichan Map" (outside site) on the Yokohama City website from April 1, 2011.

From April 1, 2011, those who newly build or rebuild should submit a “Inside Rainwater Infiltration Masu Installation Examination Confirmation Form” (PDF: 2,122KB) to the Public Works Office of each ward.
At this time, the penetration facility installation judgment map determines whether the location of the masu is suitable for penetration.

When we install rainwater infiltration masu in residential land of house and establishment, Yokohama-shi subsidizes a part of setting costs.
Rainwater infiltration masu installation subsidy system
http://translate-en.city.yokohama.lg.jp/kankyo/chisui/shintoumasu/joseikin/

• Slowly draining rainwater (rainwater penetration) effect [second report] Created on March 6, 2007
• Utilization of infiltration facility setting judgment map Created on December 5, 2006
• Past approach <approach report reflecting citizen questionnaire> [first report] Created on March 30, 2006