Internal waters hazard map

Hazard maps for floods, inland waters and high tides are summarized in onehazard map.
Please also check information about flood hazard map and hazard map high tides along with the inland water hazard map.

It is a map that summarizes various information such as areas where inundation from sewer pipes and waterways is expected during heavy rain and depth of inundation.
This map is used to facilitate smooth evacuation actions against inundation and to raise awareness of disaster prevention during normal times.

Please refer to the following "PR videos" and "PR materials" for explanations of maps and how to use them.
PR video ⇒ "Preparing for heavy rain-Utilization of inland water hazard map-(outside site)"
　　　　　「Preparing for heavy rains Use of the inland flood map (outside site) "(English)
　　　　　"Heavy rain-prevention suppression control ground map ~ (outside site)" (External version)
　　　　　"Because the big help ~ Insurance Hazard Map Utilization ~ (outside site)" (HTML)
PR document ⇒ "Let's prepare for the increasing heavy rain using the inland water hazard map! （PDF：1,317KB）」
※Inland water: Heavy rain fills sewer pipes and waterways, and water overflows from manholes and rainwater masu.
※Flood: The water level of the river rises as heavy rains continue to rise, exceeding the dike and overflowing with river water due to the collapse of the dike.

Effective June 28, 2021, it was revised to inland water hazard map when the largest possible rainfall (153 mm per hour) occurs.

When searching from Address, etc., and detailed drawings are available.
Please utilize "Yokohama-shi administration map reporting system (Wai Wai disaster prevention map) (outside site)".
・Residential land lower than roads, such as basements and underground parking lots, may have a risk of rainwater entering regardless of the degree of flooding.
・Depending on the strength of the rain and how it falls, the flooded area and inundation depth may differ from the assumption.
・The inundation assumption of the inland water hazard map is based on the status of maintenance of rivers and sewers at the end of FY2018.
・The "Yokohama City Administrative Map Information Providing System (Wai Wai Disaster Prevention Map)" allows you to check the inundation depth of any point calculated by the inundation simulation as reference information and the ground height (TP) used for calculation. Please confirm "Click here (PDF: 1,028KB)" for confirmation method.

Due to a partial revision of the Enforcement Regulations of the Housing Lots and Buildings Transaction Business Law (enforced on August 28, 2020), the location of residential land or buildings subject to transactions in the flood hazard map created under the Flood Control Law has been newly positioned as an item to explain important matters.

Although the inland water hazard map of Yokohama City is not based on the Flood Control Law, when dealing with residential land or buildings, please present the inland water hazard map here so that the other party can grasp the flood risk and provide information on the location of residential land and buildings subject to the transaction so that it can be used for evacuation actions to heavy rain etc.

[Important Notice]
Inland water hazard map is not only expected to absorb water in your area.

・How to obtain necessary information in the event of a disaster and how to prepare on a daily basis
・Precautions for heavy rain and how to think about evacuation
・Mechanisms of inland flooding and flooding (river flooding)
・Actions to be taken when evacuation information comes out
It's important to note. Please be sure to check it along with the map.

↓↓↓Click here for download.↓↓↓

Information side (common to all wards) (PDF: 5,660KB)

※Map surfaces of each ward have been updated according to the content of the flooded hazard map (Update date: June 1, 2022)
　Inundation (inland water, flood, high tides) hazard map has created a paper map. When you want reading on paper, please see in city hall the third floor citizen information room center.
　Click here for the flooded hazard map

Disasters in Yokohama City
(Flood history, etc. can be checked here.)
Frequently Asked Questions (PDF: 705KB)
(The content of frequently asked questions has been updated. Date of renewal: June 30, 2023
Inland water hazard map
(You can check past inland water hazard map here.)
Inland water hazard map interview video (outside site)
(We interviewed National Research and Development Agency Institute of Disaster Prevention Science about inundation inland water.)