In a series of storms wreaking havoc across a wide swath of Kyushu, an enormous number of trees and logs flowing from forests to residential areas have been blamed by authorities and experts for the large-scale devastation.
The torrential rains have triggered landslides and floods in Fukuoka and Oita prefectures in northern Kyushu since last week, leaving at least 27 confirmed dead and many others still missing.
Kyoko Maruyama recounted her fear when she witnessed a number of fallen trees flowing in water crash into her house in Asakura, Fukuoka Prefecture, on the night of July 5. Maruyama, 73, said she was dragged into muddy water as the large driftwood logs kept hitting her limbs before her son pulled her to safety and pushed her upstairs.
The following morning, a large amount of driftwood had piled up on the muddy streets and rice paddies. Dai Sasaki, a 43-year-old interior designer in the city, said his house had been “ripped from the foundation” by the trees.
Forestry is a mainstay industry in mountainous parts of the disaster-affected area and many cedar and cypress trees were planted during the economic recovery after World War II. Local government officials and academics believe that during the storm the forceful flow of mud and debris from the forests carried along with it not only felled trees but standing trees as well.
Recovery workers were struggling to get rid of the trees, which had been sticking out of sludge and blocking road traffic. This caused access to be cut to many communities, hindering search and rescue operations.
“The trees are a big obstacle to recovery” in the disaster-hit areas, said Jun Matsumoto, disaster management minister, adding that the government sees a need to increase the pace of tree removal work.
Prime Minister Shinzo Abe visited some disaster-hit areas Wednesday and pledged that the government will do its utmost to help recovery efforts.
Routes were reopened to stranded communities in Fukuoka Prefecture on Tuesday.
More than 20 people remain unaccounted for as of Wednesday, according to local governments.
Shinichiro Yano, an expert on river engineering, said a set of adverse conditions such as unusually heavy downpours caused landslides almost everywhere.
Even trees with trunks measuring 50 to 60 cm in diameter were washed away by the roots, the professor at Kyushu University in Fukuoka said. “The trees blocked the water stream, caused floods and made the damage worse,” Yano said.
Yano said coniferous trees such as cedar are relatively light and can easily drift on water, and that the power of fast-floating trees likely destroyed a bridge on the Kyudai Line of Kyushu Railway Co. in Hita, Oita Prefecture.
“Drifting trees ended up hitting the bridge piers one after another and the structures could not withstand (the impact),” Yano said.
Experts also point to the piles of logs left in the forest as a result of thinning efforts before the disaster.
“It is common” for such timber to be left untouched in forests, an official of the city of Asakura said. Companies in the forestry industry cannot afford to remove the logs in a cash crunch caused by an influx of cheaper lumber from overseas, the official said.
Masato Miki, a 70-year-old carpenter in the city, criticized authorities for not learning lessons from a storm that hit northern parts of Kyushu five years ago. “A lot of logs left untouched drifted at that time,” Miki said.
Forestry minister Yuji Yamamoto pledged Tuesday to set up a task force to deal with the destruction caused by large driftwood.
Yoshiteru Murosaki, head of the Education Center for Disaster Reduction under the University of Hyogo, warned other municipalities outside of the current disaster area to brace for potential damage caused by logs in storms.
“A large amount of drifting logs can cause serious damage and that could happen anywhere,” Murosaki said. “We should get to the bottom of how disasters unfold and how to deal with them.”