What is the Flood Hazard Map (Flood, Inland Water, high tides)?

Last Updated October 1, 2024

What is an inundation hazard map?

　In Yokohama City, three hazard maps, flood, inland water, and high tides, are compiled into one volume.

About three types of hazard maps

Flood Hazard Map

Based on the 　Flood Control Law (Article 15 of the Flood Control Law, Article 11 of the Enforcement Regulations of the Act), in order to ensure smooth and prompt evacuation during floods, flooding is expected when rivers are flooded due to rainfall of the largest possible scale etc. Information such as evacuation shelters is displayed in the flood inundation area map that displays the assumed flood inundation area and the assumed water depth.

Inland water hazard map

　It is a map that summarizes various information such as the area where inundation from sewer pipes and waterways is expected and the depth of inundation due to the largest possible rainfall (153 mm per hour).
　The inland water hazard map of Yokohama City is not based on the Flood Control Law, but it is created to use it for smooth evacuation actions against flooding and raising awareness of disaster prevention during normal times.
[Reference] About designation of inland water inundation assumption area
Please refer to page of making source (Sewerage River Bureau management promotion section) for detailed contents.
About inland water hazard map

high tides Hazard Map

In accordance with 　the Flood Control Law (Article 15 of the Flood Control Law and Article 11 of the Enforcement Regulations of the Act), information on evacuation centers and other facilities is shown in the high tides inundation area map, which shows the estimated depth of water in the event of a high tides of the largest possiblehigh tides,high tides, and other areas.
(Basic setting conditions)
　（1） Assuming the largest typhoon in Japan (the central pressure of the Muroto typhoon)
　（2） We will consider the conditions of typhoon routes, speeds, and radius, and select typhoons that have a greater impact.
　（3） Consider flooding in rivers at the same time as high tides
　（4） Assuming the worst situation, anticipate a breach of a levee, etc. (considering cases where it does not break)
※high tides Inundation Area Map (10 Wards): Tsurumi Ward, Kanagawa Ward, Nishi Ward, Naka Ward, Minami Ward, Hodogaya Ward, Isogo Ward, Kanazawa Ward, Kohoku Ward, Konan Ward
[Reference] About designation of high tides inundation area
For more information, please refer to the following link.
・ Kanagawa homepage "About high tides inundation area along Tokyo Bay coast" (outside site) (outside site)
・ Kanagawa homepage "high tides inundation assumption area map" (outside site) (outside site)

Update information

[October 1, 2024] The inundation hazard map has been updated following the review of the high tides inundation area in Kanagawa Prefecture. (New Konan Ward has been added to the high tides Inundation Area.) * There is no change in flood and inland water inundation areas.
[March 1, 2024] Sakae Ward Flood Theard Map has been updated. ※There is no change in the inundation area.
[June 1, 2022] We released inundation hazard maps of 15 wards of the city (other than Kanagawa Ward, Kanazawa Ward and Sakae Ward).
[September 2021] We released inundation hazard map of Sakae Ward.
[August 12, 2021] In the Kanagawa Ward Hazard Map, there was an error in the location of the elementary school (Koyasu Elementary School). [June 28, 2021] We released flood hazard maps of Kanagawa Ward and Kanazawa Ward.
[September 18, 2020] Hazard maps for Tsurumi Ward, Kohoku Ward, Midori Ward, Aoba Ward and Tsuzuki Ward have been updated. (There is no change in the inundation area on the map.)

Explanation on the Flood Control Law (explanation of important matters, etc.)

Due to a partial revision of the Enforcement Regulations of the Residential Land and Building Transaction Business Law (enforced on August 28, 2020), the location of the residential land or building subject to transaction in the flood hazard map created based on the Flood Control Law is newly described in the explanation of important matters. Will be positioned as an item.
For more information, please click here.
Explanation on the Flood Control Law (explanation of important matters, etc.)

Use the flood hazard map to create a My Timeline (evacuation action plan)!

　My Timeline is a self-evacuation action plan that has been organized in chronological order in advance according to the family structure and local environment of each person in response to disasters that may occur in the future, such as typhoons and heavy rains.
　Check the hazard map and create a My Timeline for each person.
　 ◎About my timeline (Yokohama-shi homepage)