A preliminary study on the comprehensive threshold for debris-flow early warning

Abstract

Debris-flows not only cause a great loss of property, but also kill and injure people every rainy season in the mountainous regions of China. In order to reduce hazard and risk, several methods of assessing rainfall thresholds have been provided at present, based on statistical models. However, the limited rainfall data with debris-flow occurrence or non-occurrence makes threshold analyses very difficult. This paper, therefore, presented a kind of comprehensive threshold consisting of pore-water pressure from Terzaghi theory, and rainfall factors from frequent usage for predicting debris-flow occurrence. Rainfall and pore pressure data has been collected in a number of locations in Wenjiagou gully to assess critical rainfall and pore pressure values for debris flow initiation. The three-level early warning criteria (Zero, Attention, and Warning) has been adopted and the corresponding judgement conditions has been defined based on monitoring data in a real-time way. Finally, it is suggested that the combination of these two critical values might be a useful approach in a warning system for safeguarding of population in debris-flow prone areas.

Evaluating critical rainfall conditions for large-scale landslides by detecting event times from seismic records

“…Although the geological and rainfall conditions in Taiwan and in other countries are not the same, seismic records can be used to obtain the timing of landslide occurrences for rainfall threshold analysis in other countries. For countries with geological and rainfall conditions similar to those of Taiwan (e.g., Japan and the Philippines; Saito and Oguchi, 2005;Yoshimatsu and Abe, 2006;Evans et al, 2007;Yumul et al, 2011), the results of this study may serve as a useful reference for the development of a forecast model for rainfall-triggered landslides.…”

“…If such ground motion is recorded by seismic stations, the timing of large landslides can be extracted from the records. In general, if the exact time of a landslide is unknown, the time point with the maximum hourly rainfall will be conjectured as the time of the landslide Wei et al, 2006;Staley et al, 2013;Yu et al, 2013;Xue and Huang, 2016). One case study examined the rainfall that triggered the Xiaolin landslide, a giant landslide in southern Taiwan that disturbed an area of ∼ 2.6 km 2 and resulted in more than 400 deaths in August 2009.…”

Reply-to-RC２

“…If such ground motion is recorded by seismic stations, the timing of large landslides can be extracted from the records. In general, if the exact time of a landslide is unknown, the time point with the maximum hourly rainfall will be conjectured as the time of the landslide (Chen et al, 2005;Wei et al, 2006;Staley et al, 2013;Yu et al, 2013;Xue and Huang, 2016). One case study examined the rainfall that triggered the Xiaolin landslide, a giant landslide in southern Taiwan that disturbed an area of ∼ 2.6 km 2 and resulted in more than 400 deaths in August 2009.…”