Journal of the Japan Society of Erosion Control Engineering, Vol.57,No.6,2005

Outburst of a small landslide dam on the Imokawa River(prompt report)

Yukio KATO, Takashi MIYANO, Takahisa MIZUYAMA

Abstract

On October 23, 2004, the Niigata‐chuetsu earthquake hit the Niigata‐chuetsu region of Niigata Prefecture, Japan causing many landslides along the Imokawa basin. Some of these landslides dammed off the flow of the Imokawa river. Wire-sensors and water level gauges were installed near these landslide dams to monitor the discharge rate of the river and to warn local residents living downstream concerning the dangers of flooding if the dams broke. In fact, a small dam burst on November 4, 2004. Its flood hydrograph was observed, and data was recorded. The flood discharge rate increased sharply for ten minutes and subsided over the next 50 minutes. Although not all possible situations are understood from the data, it did provide valuable data on predicting the peak discharge rate in the case where a landslide dam bursts.

Key words:landslide dam, outburst, flood discharge, peak discharge, Niigata‐chuetsu earthquake

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