Yutaka GONDA, Kazuya AKIYAMA, Shinya KATSURA, Kazuhiro HATADA, Masayuki HATA, Yukihiko TAKAHASHI, Osamu KIRYU, Yoji SAWA, Keisuke OZONE Yoshihiko KOIZUMI and Hiroshi KAWABE
Due to strong seasonal rain]front activity, heavy rainfall occurred in the Mid]Niigata region between July 29 and August 1, 2013. The total amount of rainfall reached approx. 400(mm) at Karuizawa observatory, Nagaoka City. From late Monday, July 29, to early Tuesday, July 30, rainfall]induced slope failures, debris flows, and floods occurred throughout the Tochio area of Nagaoka City. Early Thursday, August1,rainfall]induced slope failures occurred throughout the coastal area of Izumozaki Town and Teradomari area of Nagaoka City, resulting in one fatality. Although total amounts of rainfall in 2004 and 2013 did not differ considerably, sediment movements such as slope failures, debris flows, and floods were far more frequent in 2004 in the belt]shaped area extending from Izumozaki Town to Tochio area. Sediment movements are thought to have been less frequent in 2013, because rainfall was distributed over two distinct periods, divided by approximately two rain]free days in between. On the other hand, as much as 400(mm) accumulated within only 24 hours on Tuesday, July 13, 2004.
Key wordsFslope failure, debris flow, flood, local rainfall, seasonal rain front