Widespread flooding caused by heavy rain in Japan

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Japanese people shielding themselves from heavy rainfall with umbrellas in a city centre

Description

  • The southern Japanese Prefectures of Kagoshima and Miyazaki have seen abnormally high levels of rainfall over the last five days which have caused widespread flooding and increased the risk of landslides.
  • Over one million people are currently being evacuated from the area, including the populations of three low-lying cities: Kagoshima, Kirishima and Aira.
  • The weather has brought a stop to almost all normal services and business operations in these areas, has caused severe transport disruptions and poses a significant threat to life.
  • Any travellers caught in affected areas should heed the advice issued by local authorities and seek to relocate immediately.

Impact of widespread flooding

On Wednesday 3 July, around 800,000 people were ordered to evacuate from their homes in Kagoshima prefecture, in the southern Japanese island of Kyushu due to widespread flooding caused by five successive days of heavy monsoon-like rain. Local authorities have issued successive warnings since Friday, 28 June, and have now told urban residents to “take steps to protect their lives”, whilst the Japanese Self-Defence forces have been called in to distribute food and water, aid in evacuations, and construct temporary flood defences.

The populations of three of Kagoshima’s low-lying cities; Kagoshima, Kirishima and Aira are being relocated, whilst around 300,000 people are also being evacuated from neighbouring Miyazaki prefecture. These operations are currently ongoing, and as of 1600 local time (0700 GMT), only around 4,000 affected individuals had been evacuated according to the Fire and Disaster Management Agency.

The evacuation order follows five days of severe rainfall in southern Japan and across the East China Sea, where an unstable atmosphere has been caused by a pocket of warm air from the south meeting a seasonal rain front. This has caused very dense precipitation to fall over the south of Japan, with weather stations in Satsumasendai, Kagoshima Prefecture initially recording up to 290 millimetres of rainfall over a 12 hour period on Monday, roughly equivalent to the total average monthly rainfall for July.

At its most intense, the deluge reached a saturation point of just over 60 mm an hour in the city of Ebino, Miyazaki Prefecture. Although the Japanese rainy season typically results in heavy precipitation at this time of year, these levels are unusually dense and over the weekend records were set in both Kirishima and Hioki, where 241.5 mm and 233 mm fell in just six hours respectively.

The weather has brought almost all normal services and business operations in Kagoshima, Kirishima and Aira to a standstill, whilst many major roads and highways in Kagoshima are closed or have become in accessible due to the flood waters. Recent reports have also suggested that the national arterial route between Kagoshima and Miyazaki has been blocked following a landslide, impeding onward travel. Although a number of the Kyushu shinkansen bullet train services between the Kumamoto and Kagoshima-Chuo stations have been temporarily suspended, others are still running with severe delays.

Outlook following increased rainfall

According to the Japanese Meteorological Agency, a further 350mm of rain is expected to fall in southern Kyushu by midday on Thursday, with many areas predicted to see over 80mm of rain every hour. In addition to continued rainfall in Kagoshima and Miyazaki, flooding is also expected to affect the Chugoku region and the Hokuriku area by the end of the week due to continued heavy rainfall.

The current low pressure system is expected to remain over Japan until late on Saturday, when it will finally move north eastwards, relieving Kyushu but also increasing the risk to south-eastern areas of the main Japanese island of Hokkaido. Although flood waters are likely to begin to recede by the start of next week, the risk of mud slides will remain elevated for a loner period, as the saturated ground continues to be unstable.

This event is likely to have a negative impact on the economy of southern Kyushu in the medium term, as farmland and key production areas are damaged or destroyed. So far only one death has been reported; the result of a mudslide in Kagoshima city, although further fatalities are very likely. A similar period of heavy rainfall in July 2018, caused the deaths of around 200 people in the west of Japan and eventually led to the evacuation of two million residents by 70,000 emergency workers. It is possible that this current period of flooding could eventually have a similar impact as heavy rain continues to fall over the next few days.

Any travellers caught in affected areas should heed the advice issued by local authorities and seek to relocate immediately. Those in elevated areas should be aware that further mudslides are likely, causing further disruption. The latest weather forecasts and official advice can be accessed via the Japanese Meteorological Agency website at: https://www.jma.go.jp/jma/indexe.html