The Mainichi Shimbun answers some common questions readers may have about what measures they should take in the event of a dangerous torrential downpour during this year's rainy season.
Question: The rainy season has already started. Given many are concerned about sudden, concentrated bursts of torrential showers this year, could you tell us where we can find helpful information on what to do if caught by heavy rain?
Answer: The most convenient way is to look at the series of real-time risk maps available on the Japan Meteorological Agency (JMA)'s website. On their diagrams, regions at risk of disasters including landslides and flooding are colored according to their level of danger. The information is based on numerous sources such as rainfall predictions and geological data. Taking into consideration evacuation times, it displays color-coded warnings three hours before a predicted flood and two hours before a potential landslide. Yellow means advisory, red is warning, light purple is high risk, and deep purple is classed as extreme risk.
Q: So you can work out how at risk your local area is just by looking at the map. But timing is key with evacuation, right?
A: Following calls from the Cabinet Office, from May 2019 organizations that make warning announcements -- such as municipal governments giving official advisories to evacuate and the JMA's local observatories distributing weather forecast advisories and warnings -- have adopted measures in accordance with a five-level warning system. In response to level 3, which shows up red on the map, elderly and other at-risk residents are ordered to evacuate. At light purple level 4, all remaining residents must take their leave. At the deep purple level 5, chances of a disaster already occurring are so high that evacuation in the level 3 and 4 stages is crucial.
Q: Why was this framework put together?
A: In the torrential rain disaster that hit western Japan, municipal governments put out evacuation advisories, but those calls didn't lead to people taking action as advised. The introduction of this system stems from reflection on what happened there.
Q: Where is a good place to evacuate to?
A: Evacuating to a local government designated evacuation area, such as an elementary or middle school, a community center and other public building, is recommended. If time is limited, it is also acceptable to retreat to the upper floor of a building made with reinforced concrete. But, if you look at the hazard map and the area you're in isn't under any warnings, the safest thing to do is to wait at home. Please make regular checks to confirm if evacuation becomes a necessity.
(Japanese original by Mayumi Nobuta, Science & Environment New Department)