著者
海堀 正博 長谷川 祐治 山下 祐一 崎田 博史 中井 真司 桑田 志保 平松 晋也 地頭薗 隆 井良沢 道也 清水 収 今泉 文寿 中谷 加奈 柏原 佳明 加藤 誠章 鳥田 英司 平川 泰之 吉永 子規 田中 健路 林 拙郎
出版者
公益社団法人 砂防学会
雑誌
砂防学会誌 (ISSN:02868385)
巻号頁・発行日
vol.71, no.4, pp.49-60, 2018-11-15 (Released:2019-11-15)
参考文献数
10
被引用文献数
8

In July 2018, heavy rain due to Typhoon Prapiroon affected western Japan and caused numerous sediment disasters such as landslides and debris flows in Hiroshima Prefecture. In a southern part of Hiroshima, approx. 8,500 slope failures occurred, and total number of sediment disasters were reported as approx. 1,250. Therefore, members of Japan Society of Erosion Control Engineering and Chuushikoku branch conducted field surveys in Hiroshima City, Aki Gun, Kure City, and Higashi-hirosima City. In Kawasumi area, Aki Gun, large rock which seemed to be core stone and diameter approx. 10 m moved down from the torrent, and at downstream side 6 m diameter rock seemed to hit the house with destructive power. In Aki-Gun, Saka-Cho, Koyaura area, one old stone masonry sabo dam was destroyed. We estimated the flow discharge from the investigation at the upstream of dam and considered the flow process from the flow traces around the dam. The results showed that the dam destroying process was as following. Firstly, the large rocks accumulated at the frontal part of debris flow collided and destroyed the right bank side wing, and then stone masonry product peeled off continuously. Furthermore, debris flows occurred from several streams in Koyaura and 1-1.5 m sediment deposition occurred at downstream residential area. In Higashihiroshima City Kurose-cho, many collapses and debris flows occurred around Hiroshima International University and there were no casualties fortunately. In Kurose-cho, most of the collapses seemed to occur from the top and ridge of the mountains with gentle slope around 15 degrees.
著者
堤 大三 藤田 正治 宮本 邦明 今泉 文寿 藤本 将光 国領 ひろし 泉山 寛明
出版者
公益社団法人 土木学会
雑誌
土木学会論文集B1(水工学) (ISSN:2185467X)
巻号頁・発行日
vol.67, no.4, pp.I_721-I_726, 2011 (Released:2012-03-14)
参考文献数
5

In August 2009, the Typhoon Morakot hit Taiwan and caused an extraordinary amount of rainfall. Due to the heavy rainfall, a large number of floods and sediment-related disasters occurred all over the island. In Shaolin Village, Kaohsiung County, a huge landslide occurred around 6 am August 9, destroyed the village completely and killed more than 500 people. After the landslide, authors visited the landslide site and investigated the landslide scour to collect information on factors affecting landslide occurrence such as exposed bedrock and soil layer conditions. GIS analysis using DEM data were also conducted to determine the sliding domain. According to the site investigation and GIS analysis, rainwater infiltration analysis and slope stability analysis were conducted. Results of the analysis suggested that the landslide domain, about 1,200 m long, 500 m wide and 80 m deep was collapsed by multi phased manner.
著者
松岡 憲知 今泉 文寿 西井 稜子
出版者
公益社団法人 東京地学協会
雑誌
地学雑誌 (ISSN:0022135X)
巻号頁・発行日
vol.122, no.4, pp.591-614, 2013-08-25 (Released:2013-09-11)
参考文献数
127
被引用文献数
5 6

This review paper synthesizes geomorphic dynamics, sediment transport and resulting natural hazards in mountains of the southern Japanese Alps and their drainage basins, where climatic and geological situations produce highly active landform dynamics. In alpine areas above the timber line, shallow diurnal freeze-thaw action operating in the thin topsoil produces small-scale periglacial forms, and gravitational spreading leads to numerous sackung features where snow-melt and heavy rain in places promote rockslides. In subalpine and montane areas, deep-seated landslides originate from fractured sedimentary rocks, deep V-shaped valleys, and heavy rain, while shallow landslides continue with historical forest clearance. Continuous slope failures prevent vegetation recovery and maintain debris input to valleys. Steep valleys contribute to high-density debris flows. Frequent or repetitive occurrences of these mass movements promote continuous denudation of slopes, rockfall accidents along hiking trails, and sedimentation at artificial dams. They occasionally cause significant hazards to villages further downstream. Predicting and mitigating slope hazards require distinguishing among annual, low-magnitude processes, episodic high-magnitude processes and geomorphic changes associated with long-term climate change.
著者
今泉 文寿 早川 裕弌 經隆 悠 堀田 紀文
出版者
日本地球惑星科学連合
雑誌
日本地球惑星科学連合2019年大会
巻号頁・発行日
2019-03-14

土石流はその速度,移動距離,破壊力から,甚大な災害を引き起こす土砂移動現象である。土石流の発生・流下特性は土石流の材料となりうる不安定土砂の土石流発生域における貯留状況の影響を受けていると考えられるが,土石流の発生域はアクセスが困難であり,また危険性が伴うことからほとんど明らかになっていない。そこで静岡県北部の大谷崩において,定期的な地上レーザースキャンやUAV撮影,現地観測によって不安定土砂の貯留状況が土石流の発生・流下特性へ及ぼす影響について調べた。その結果,土石流の発生位置は不安定土砂の堆積状況,および支流から土石流渓流への水の供給の影響を受けていることがわかった。土石流発生域においては渓床勾配が急なことから不飽和土石流が重要な流動形態である。さらに堆積土砂量が15,000m3を超えるときには不飽和土石流が,10,000 m3を下回るときには飽和土石流が多く発生した。また,流動形態は流下とともに変化をすることが明らかになった。このように,土石流の発生・流下特性は発生域における不安定土砂の堆積状況の影響を受け,さらに流下・堆積域で観測される土石流と流下形態が異なることがあることが明らかになった。