Both Tokyo and Osaka are seaside cities with a number of large and small rivers, which makes them vulnerable to flooding after heavy rains.
Local government websites have hazard maps that demarcate the areas most likely to flood, especially when major rivers overflow. Unfortunately, for people who don’t read Japanese, only few of the local maps are in English.
In general, dark blue denotes areas most likely to flood. However, the color legend of the maps does vary from ward to ward so if you can’t read Japanese, please note the numbers of water height to gauge the water-level legend or ask a Japanese speaker to help you.
When severe weather conditions occur, it’s recommended that you check the official advisories and warnings on Japan Meteorological Agency website.
For a detailed map of other regions, see the hazard map portal of the Japan’s transportation ministry.
Hazard maps of Tokyo
Chiyoda Ward 千代田区
Chuo Ward 中央区
- If Sumidagawa River (隅田川), Kandagawa River (神田川) and Nihonbashigawa River (日本橋川) are flooded
- If Arakawa River overflows
Minato Ward 港区
Shinjuku Ward 新宿区
Bunkyo Ward 文京区
Taito Ward 台東区
Sumida Ward 墨田区
Koto Ward 江東区
Shinagawa Ward 品川区
Meguro Ward 目黒区
Ota Ward 大田区
- If Nomigawa River (呑川), Uchikawa River (内川) and Marukogawa River (丸子川) overflow
- If Tamagawa River (多摩川) overflows
Setagaya Ward 世田谷区
Shibuya Ward 渋谷区
Nakano Ward 中野区
Suginami Ward 杉並区
Toshima Ward 豊島区
Kita Ward 北区
- If Arakawa River (荒川) overflows
- If Sumidagawa River (隅田川), Shingashigawa River (新河岸川), Shakujiigawa River (石神井川) and Kandagawa River (神田川) overflow
Arakawa Ward 荒川区
Itabashi Ward 板橋区
- If Arakawa River (荒川) overflows
- If Shingashigawa River (新河岸川), Shakujiigawa River (石神井川) and Shirakogawa River (白子川) overflow
Nerima Ward 練馬区
Adachi Ward 足立区
- In the case of severe rainfall
- If Tonegawa River (利根川) overflows
- If Edogawa River (江戸川) overflows
- If Arakawa River (荒川) overflows
- If Nakagawa River(中川), Ayasegawa River (綾瀬川), Shibakawa (芝川) and Shinshibakawa (新芝川) overflow
Katsushika Ward 葛飾区
Edogawa Ward 江戸川区
- If the case of severe rainfall
- If Edogawa River (江戸川), Tonegawa River (利根川) and Arakawa River (荒川) overflow
Hazard maps of Osaka
Kita Ward 北区
Miyakojima Ward 都島区
Fukushima Ward 福島区
Konohana Ward 此花区
Chuo Ward 中央区
Nishi Ward 西区
Minato Ward 港区
Taisho Ward 大正区
Tennoji Ward 天王寺区
Naniwa Ward 浪速区
Nishi-Yodogawa Ward 西淀川区
Yodogawa Ward 淀川区
Higashi-Yodogawa Ward 東淀川区
Higashinari Ward 東成区
Ikuno Ward 生野区
Asahi Ward 旭区
Joto Ward 城東区
Tsurumi Ward 鶴見区
Abeno Ward 阿倍野区
Suminoe Ward 住之江区
Sumiyoshi Ward 住吉区
Higashi-Sumiyoshi Ward 東住吉区
Hirano Ward 平野区
Nishinari Ward 西成区