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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-333
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
28 Sep 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).
Technical notes: Rainfall threshold calculation for debris flow early warning in areas with scarcity of data
Hua-li Pan1,2, Yuan-jun Jiang1,2, Jun Wang3, and Guo-qiang Ou1,2 1Key Laboratory of Mountain Hazards and Earth Surface Process, Chinese Academy of Sciences, Chengdu 610041, China
2Institute of Mountain H azards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
3Guangzhou Institute of Geography, Guangzhou 510070, China
Abstract. Debris flows are one of the natural disasters that frequently occur in mountain areas, usually accompanied by serious loss of lives and properties. One of the most used approaches to mitigate the risk associated to debris flows is the implementation of early warning systems based on well calibrated rainfall thresholds. However, many mountainous areas have little data regarding rainfall and hazards, especially in debris flow forming regions. Therefore, the traditional statistical analysis method that determines the empirical relationship between rainfall and debris flow events cannot be effectively used to calculate reliable rainfall thre-shold in these areas. To solve this problem, this paper developed a quantitative method to identify rainfall threshold for debris flow early warning in data-poor areas based on the initiation mechanism of hydraulic-driven debris flow. First, we studied the characteristics of the study area, including meteorology, hydrology, topography and physical characteristics of the loose solid materials. Then, the rainfall threshold was calculated by the initiation me-chanism of the hydraulic debris flow. The results show that the proposed rainfall threshold curve is a function of the antecedent precipitation index and 1-h rainfall. The function is a line with a negative slope. To test the proposed method, we selected the Guojuanyan gully, a typical debris flow valley that during the 2008–2013 period experienced several debris flow events and that is located in the meizoseismal areas of Wenchuan earthquake, as a case study. We compared the calculated threshold with observation data, showing that the accuracy of the method is satisfying and thus can be used for debris flow early warning in areas with scaricty of data.

Citation: Pan, H.-L., Jiang, Y.-J., Wang, J., and Ou, G.-Q.: Technical notes: Rainfall threshold calculation for debris flow early warning in areas with scarcity of data, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-333, in review, 2017.
Hua-li Pan et al.
Hua-li Pan et al.
Hua-li Pan et al.

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Short summary
Debris flow early warning always based on well calibrated rainfall thresholds. While for area where historical data is very insufficent to determine a rainfall threshold, it is necessary to develop a method to obtain the threshold by simplily using limited data. A quantitive method, a new thinking, to calculate the rainfall thershold is developed in this study, which combined the initiation mechanism of hydraulic-driven debris flow with the runoff yield and concentration laws of the watershed.
Debris flow early warning always based on well calibrated rainfall thresholds. While for area...
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