Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-265
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
28 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Debris flow initiation characteristics and occurrence probability after extreme rainfalls: case study in the Chenyulan watershed, Taiwan
Jinn-Chyi Chen1, Jiang-Guao Jiang1, Wien-Shun Huang2, and Yuan-Fan Tsai3 1Department of Environmental and Hazards - Resistant Design, Huafan University, Taipei 22301, Taiwan
2Ecological Soil and Water Conservation Research Center, National Cheng Kung University, Tainan 70101, Taiwan
3Department of Social and Regional Development, National Taipei University of Education, Taipei 10671, Taiwan
Abstract. Rainfall and other extreme events often trigger debris flows. This study examines the debris flow initiation characteristics and probability of debris flow occurrence after extreme rainfalls. The Chenyulan watershed, central Taiwan, which has suffered from the Chi-Chi earthquake (CCE) and extreme rainfalls, was selected as a study area. The rainfall index (RI) was used to analyze the return period (T) and characteristics of debris flow occurrence after extreme rainfalls. The characteristics of debris flow occurrence included the variation in critical RI, threshold of RI for debris flow initiation, and recovery period (t0), the time required for the lowered threshold to return to the original threshold. The variations in critical RI after extreme rainfall and t0 associated with RI were presented. The critical RI threshold was reduced in the years following an extreme rainfall event. The reduction in RI as well as t0 were influenced by the RI. Reduced RI values showed an increasing trend over time, and it gradually return to initial RI. The empirical relationship between the probability of debris flow occurrence (P) and corresponding T of the rainfall characteristics for areas affected by extreme rainfalls and affected by the CCE were developed. Finally, a method for determining the P of a rainfall event was proposed based on the relationship between P and T. This method was successfully applied to evaluate the probability of debris flow occurrence after extreme rainfalls.

Citation: Chen, J.-C., Jiang, J.-G., Huang, W.-S., and Tsai, Y.-F.: Debris flow initiation characteristics and occurrence probability after extreme rainfalls: case study in the Chenyulan watershed, Taiwan, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-265, in review, 2017.
Jinn-Chyi Chen et al.
Jinn-Chyi Chen et al.
Jinn-Chyi Chen et al.

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