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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-2017-390
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
03 Nov 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).
Multiply factors driving continual post-wildfire debris flows with varied rainfall thresholds in the Reneyong Valley, southwestern China
Mingfeng Deng1,2, Yong Zhang1,2, Mei Liu1,2, Yuanhuan Wang3, Wanyin Xie3, and Ningsheng Chen1 1Key Laboratory of Mountain Hazards and Surface Process, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, P. R. China
2University of Chinese Academic of Sciences, Beijing 100049, China
3Sichuan Institute of Geological Engineering Investigation, Chengdu, 610072, P. R. China
Abstract. In early June of 2014, wildfire struck the Reneyong Valley in the central Hengduan Mountains of southwestern China. Three days after the wildfire, the first debris flow was triggered in branch No. 3, followed by 2 other debris flows that same year. In August 2015, another debris flow occurred in branches No. 1, No. 2 and No. 3, respectively. Rainfall data from three nearby rain gauges and rainfall totals speculated from debris flow volume suggest the three debris flows in 2014 were generated by isolated convective rainfall. Later, we found that varied rainfall thresholds existed among the branches and that these thresholds might be related to the geological and geomorphic characteristics. The results show that (1) the thresholds of post-fire debris flows tend to increase as time passes; (2) post-fire debris flows in the Reneyong Valley occur with high frequency not only because of the loss of the natural canopy, the occurrences of an ash layer and dry ravels and an increase in soil water repellency but also because of the geology, drainage area, channel gradient and regional arid climate, which may not be affected by wildfire; and (3) the varied rainfall thresholds among the different branches are dependent on the drainage area, as entrainment is controlled by the magnitude of discharge.

Citation: Deng, M., Zhang, Y., Liu, M., Wang, Y., Xie, W., and Chen, N.: Multiply factors driving continual post-wildfire debris flows with varied rainfall thresholds in the Reneyong Valley, southwestern China, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-390, in review, 2017.
Mingfeng Deng et al.
Mingfeng Deng et al.
Mingfeng Deng et al.

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Short summary
Research of the post-wildfire in Reneyong Valley shows: (1) the thresholds of post-fire debris flows was low and tend to increase as time passes; (2) reason for the post-fire debris flows with high frequency lies in an increase in soil water repellency, the soft geology, drainage area, channel gradient and regional arid climate; and (3) the varied rainfall thresholds (low in branch No. 3 and higher in branch No. 1 and No. 2) among the different branches are dependent on the drainage area.
Research of the post-wildfire in Reneyong Valley shows: (1) the thresholds of post-fire debris...
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