“Atmospheric pressure arrangement like the end of the rainy season” Recorded heavy rain on August 28 at 18:42

Due to the active front, there has been a record heavy rain in northern Kyushu, causing inundation and sediment disasters. In the northern part of Kyushu, the moist air that flowed around the Pacific high pressure continued to flow, and the atmospheric pressure arrangement was like the end of the rainy season.

"Linear precipitation zone" in northern Kyushu

According to the Japan Meteorological Agency, when the Pacific high pressure gradually changes from summer to autumn, it gradually weakens and retreats to the southeast. In western Japan, the front line is stagnant mainly in the northern part of Kyushu.

Last week, warm and humid air brought in by Typhoon No. 11 approaching the Sakishima Islands flowed in from the west, leading to active frontal activity, and an active rain cloud called the “Linear Precipitation Zone” was applied to northern Kyushu. Continued.

According to the Japan Meteorological Agency, these atmospheric pressure arrangements will continue until around the 30th, so the front is expected to stagnate, and even if the rain has weakened, there is a risk of heavy rain again, calling for continued vigilance.

The possibility of the occurrence of “inland flooding”

Prof. Koichiro Ogushi of Saga University has pointed out that record heavy rain and high tide time in the Ariake Sea overlapped in Saga Prefecture.

On top of that, he pointed out that “the embankment is under heavy load and there is a risk of flooding depending on the rain in the future. Even if the water level drops, it is necessary to continue to be vigilant.”

According to Professor Ogushi, “The Rokkaku River basin, which flows from east to west in the south of Saga Prefecture, is a low land with a zero-meter zone above sea level, and when the Ariake Sea is at high tide, it is a place where the wide area is lower than the sea level. "It seems that the rivers increased due to the heavy rainy seasons, which led to flooding."

Furthermore, the plains of the basin are poorly drained, and the drainage of water that has accumulated in small rivers and irrigation canals is not in time, resulting in the occurrence of “inland water flooding” and the damage may have spread.

On top of that, Professor Ogushi said, “There is information that there is a crack in the levee due to this heavy rain, and it is thought that there is a heavy load. Depending on the rain in the future, the water level will rise again and there is a risk of breakdown etc. Some people in the basin still need to be vigilant. ”

The area around Takeo is a flood-prone area

Prof. Yukihiro Shimatani, professor at the Graduate School of Kyushu University, who headed the Takeo River Office of the Ministry of Land, Infrastructure, Transport and Tourism in Saga Prefecture, stated, It ’s easy, and if it rains at high tide, there is a risk of flooding again, so watch out. ”

According to Prof. Shimatani, the area around Takeo City, where flood damage has occurred, is an area where the slope of the land is gentle and the drainage is poor, and it is a “flooding area where flood damage has occurred repeatedly in the past”.

When it rains, the rainwater that has accumulated in the residential area is drained to the “Rokukaku River” that flows from Takeo City to the Ariake Sea. However, if the risk of flooding increases, the pump must be stopped. "Water flooding" occurs.

Furthermore, the hexagonal river has a gentle slope and is affected by the tide level from the estuary to more than 20 kilometers upstream, so even if the water level drops and drainage to the river resumes, the high tide time zone Again, there is a risk that the river level will rise and drainage will not be possible.

Prof. Shimatani said, “It is thought that the critical situation of the river flooding has passed once, but if it becomes impossible to drain again in the future, there is a risk of new inundation damage or a prolonged period of time. "

Temporarily stop drain pump when water level rises

According to the Kyushu Regional Development Bureau, the Ministry of Land, Infrastructure, Transport and Tourism, there are 60 pumps for draining rainwater that has fallen in residential areas into the river basin of the Rokkaku River and Ushizu River that flow through Saga Prefecture. This time, because the river level rose due to record heavy rain, the drainage was stopped sequentially after 5 am on the 28th, and the pumps at 24 locations stopped draining for a maximum of one time.

After that, the water level of the river went down, so we are now resuming drainage by the pump.