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Controls on fluvial evacuation of sediment from earthquake-triggered landslides

Wang Jin, Jin Zhangdong, Robert G. Hilton, Zhang Fei, Alexander L. Densmore, Gen Li and A. Joshua West
Controls on fluvial evacuation of sediment from earthquake-triggered landslides
Geology (Boulder) (February 2015) 43 (2): 115-118


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 M (sub w) 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 3-7X compared to 2006-2007. However, the total 2008-2012 export (92.5 + or - 9.3 Mt from 68,719 km (super 2) ) 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 (super -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.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 43
Serial Issue: 2
Title: Controls on fluvial evacuation of sediment from earthquake-triggered landslides
Affiliation: Chinese Academy of Sciences, Institute of Earth Environment, Laboratory of Loess and Quaternary Geology, Xi'an, China
Pages: 115-118
Published: 201502
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 23
Accession Number: 2015-016278
Categories: Environmental geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015048
Illustration Description: illus. incl. geol. sketch map
N20°00'00" - N53°00'00", E74°00'00" - E135°00'00"
Secondary Affiliation: Durham University, GBR, United KingdomUniversity of Southern California, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201508
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