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Controls on fluvial evacuation of sediment from earthquake-triggered landslides

Wang, J.; Jin, Z.; Hilton, R.G.; Zhang, F.; Densmore, A.L.; Li, G.; West, A.J.

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Authors

J. Wang

Z. Jin

R.G. Hilton

F. Zhang

G. Li

A.J. West



Abstract

Large earthquakes in active mountain belts can trigger landslides, which mobilize large volumes of clastic sediment. Delivery of this material to river channels may result in aggradation and flooding, while sediment residing on hillslopes may increase the likelihood of subsequent landslides and debris flows. Despite recognition of these processes, the controls on the residence time of coseismic landslide sediment in river catchments remain poorly understood. Here we assess the residence time of fine-grained (<0.25 mm) landslide sediment mobilized by the C.E. 2008 Mw 7.9 Wenchuan earthquake, China, using daily suspended sediment discharge measured in 16 river catchments from 2006–2012. Following the earthquake, suspended sediment discharge was elevated 3–7× compared to 2006–2007. However, the total 2008–2012 export (92.5 ± 9.3 Mt from 68,719 km2) was much less than estimates of fine-grained sediment input by coseismic landslides (480 +350/–338 Mt) determined by landslide area-volume scaling and deposit grain-size distributions. We estimate the residence time of fine-grained sediment in the affected river catchments using the post-earthquake rate of sediment export, and find that it ranges from one year to over a century. The first-order variability in fine-sediment residence time is proportional to the areal extent of coseismic landsliding, and is inversely proportional to the frequency of intense runoff events (>5 mm day–1). Together with previous observations from the C.E. 1999 Chi-Chi earthquake in Taiwan, our results demonstrate the importance of landslide density and runoff intensity in setting the duration of earthquake-triggered landslide impacts on river systems.

Citation

Wang, J., Jin, Z., Hilton, R., Zhang, F., Densmore, A., Li, G., & West, A. (2015). Controls on fluvial evacuation of sediment from earthquake-triggered landslides. Geology, 43(2), 115-118. https://doi.org/10.1130/g36157.1

Journal Article Type Article
Acceptance Date Nov 5, 2014
Online Publication Date Feb 1, 2015
Publication Date Feb 1, 2015
Deposit Date Jan 22, 2015
Publicly Available Date Jan 30, 2015
Journal Geology
Print ISSN 0091-7613
Electronic ISSN 1943-2682
Publisher Geological Society of America
Peer Reviewed Peer Reviewed
Volume 43
Issue 2
Pages 115-118
DOI https://doi.org/10.1130/g36157.1
Public URL https://durham-repository.worktribe.com/output/1416256

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