Typhoon No.19 Points to note about river flooding and landslides October 11th 20:06

Typhoon No. 19 may be comparable to the “Kanogawa Typhoon” in which floods and earth and sand disasters have continued in the Izu Islands and Kanto, causing more than 1,200 victims. Summary of important points.

Medium and small rivers Most alert

When it rains heavily in a short period of time, it is the flooding of small and medium-sized rivers that flow through mountains and cities.

Ototoshi In July, the “Kyushu northern heavy rain” caused flooding in small and medium-sized rivers in the mountains, causing serious damage.

Small and medium-sized rivers are characterized by a sharp rise in water level in a short time because the river width is narrow and the slope is steep.

In particular, when a flood occurs in a mountainous area, there is a risk that houses will be washed away along with a large amount of sediment and driftwood.

In small and medium-sized rivers, there are many places where “water level gauges” are not installed, and “flooding risk information” may not be announced. Please use "distribution".

In addition, try to evacuate early when the situation is different from usual, such as when the water level of the river increases and the flow becomes intense, or driftwood and stones are mixed.

Check the big river hazard map

If heavy rain continues for a long time, the rain that falls upstream flows downstream and the risk of flooding a large river increases.

First of all, it is important to check the risks using the hazard map published by local governments.

In Makita, Kurashiki City, Okayama Prefecture, where the river embankment broke down due to the heavy rain in western Japan last July, the hazard map assumption and the actual flooded area were almost the same.

The hazard map shows the inundation depth in addition to the expected inundation range due to heavy rain, and consider evacuation by referring to the risk indicated on the map.

In the case of large rivers, the country and prefectures that manage the rivers will collaborate with the meteorological observatory to jointly announce “flooding risk information” when the risk of flooding increases.

When this information comes out, it is important to evacuate early, paying attention to local government information.

If it is dangerous to move to an evacuation site or if you do not have time to do so, you may be able to ensure safety by moving to a higher location nearby.

Sediment disasters Even if you are away from slopes

In the heavy rain in western Japan last July, about 90% of the places where deaths were caused by landslide disasters were places where danger was pointed out in advance, such as the “Sediment-related Disaster Warning Area”.

It is important to note that there are cases where the disaster is designated as a sediment-related disaster warning area not only near slopes and cliffs, but also at relatively remote locations, and damage is occurring one after another.

First of all, please check if your place is a place where there is a risk of landslide disaster by using “hazard map”.

"Earthquake disaster warning information" evacuates early

When the risk of landslide disasters increases so much, the meteorological observatory and prefectures will jointly announce “Sediment-related Disaster Warning Information”.

If you live in a place where there is a risk of earth and sand disaster, please evacuate early, paying attention to the information of the local government when this information is announced.

Predictors of earth and sand disasters

Sediment disasters can occur suddenly even if landslide warning information and evacuation information have not been announced.

Before a landslide disaster occurs,
▽ Pebbles fall from the slope ▽ Cracks on the slope ▽ Water suddenly springs from the slope ▽ Water in the river suddenly decreases ▽ "Sound of the mountain" and "earth sound" may be heard.

If you notice this unusual phenomenon, immediately move away from cliffs and slopes to ensure safety.

However, it is dangerous to approach cliffs and slopes in order to check these precursors.

It is also important to note that there are no precursors.