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Testing monsoonal controls on bedrock river incision in the Himalaya and Eastern Tibet with a stochastic-threshold stream power model

Scherler, Dirk and DiBiase, Roman A. and Fisher, G. Burch and Avouac, Jean-Philippe (2017) Testing monsoonal controls on bedrock river incision in the Himalaya and Eastern Tibet with a stochastic-threshold stream power model. Journal of Geophysical Research. Earth Surface, 122 (7). pp. 1389-1429. ISSN 2169-9003. http://resolver.caltech.edu/CaltechAUTHORS:20170831-074652571

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Abstract

^(10)Be-derived catchment average erosion rates from the Himalaya and Eastern Tibet show different relationships with normalized channel steepness index (k_(sn)), suggesting differences in erosional efficiency of bedrock river incision. We used a threshold stream power model (SPM) combined with a stochastic distribution of discharges to explore the extent to which this observation can be explained by differences in the mean and variability of discharge between the two regions. Based on the analysis of 199 daily discharge records (record lengths 3–45 years; average 18.5 years), we parameterized monsoonal discharge with a weighted sum of two inverse gamma distributions. During both high- and low-flow conditions, annual and interannual discharge variabilities are similarly low in each region. Channel widths for 36 rivers indicate, on average, 25% wider streams in Eastern Tibet than in the Himalaya. Because most catchments with ^(10)Be data are not gauged, we constrained mean annual discharge in these catchments using gridded precipitation data sets that we calibrated to the available discharge records. Comparing ^(10)Be-derived with modeled erosion rates, the stochastic-threshold SPM explains regional differences better than a simple SPM based on drainage area or mean annual runoff. Systematic differences at small k_(sn) values can be reconciled with k_(sn)-dependent erosion thresholds, whereas substantial scatter for high k_(sn) values persists, likely due to methodological limitations. Sensitivity analysis of the stochastic-threshold SPM calibrated to the Himalaya indicates that changes in the duration or strength of summer monsoon precipitation have the largest effect on erosional efficiency, while changes in monsoonal discharge variability have almost no effect. The modeling approach presented in this study can in principle be used to assess the impact of precipitation changes on erosion.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/2016JF004011DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2016JF004011/abstractPublisherArticle
ORCID:
AuthorORCID
Scherler, Dirk0000-0003-3911-2803
DiBiase, Roman A.0000-0002-5347-8396
Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 2017 American Geophysical Union. Received 1 JUL 2016; Accepted 8 JUN 2017; Accepted article online 21 JUN 2017; Published online 27 JUL 2017. This project was partly supported by the Gordon and Betty Moore Foundation, through grant GBMF 423.01 to the Tectonics Observatory and NSF grant EAR0838495. D. Scherler was supported by a Feodor Lynen Research Scholarship through the Alexander von Humboldt Foundation. We thank Dimitri Lague, Pierre Valla, and two anonymous reviewers, as well as AE Mikaël Attal and Editor John Buffington for their constructive comments that helped to improve the manuscript. All cosmogenic nuclide data, the data related to discharge variability and channel widths, shown in the figures and tables, can be found in the supporting material. Gridded precipitation data sets are available from the cited references.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
Gordon and Betty Moore Foundation423.01
NSFEAR-0838495
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:river incision; stream power; discharge variability; cosmogenic nuclides; Himalaya; climate change
Record Number:CaltechAUTHORS:20170831-074652571
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170831-074652571
Official Citation:Scherler, D., R. A. DiBiase, G. B. Fisher, and J.-P. Avouac (2017), Testing monsoonal controls on bedrock river incision in the Himalaya and Eastern Tibet with a stochastic-threshold stream power model, J. Geophys. Res. Earth Surf., 122, 1389–1429, doi:10.1002/2016JF004011
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81008
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:31 Aug 2017 15:54
Last Modified:31 Aug 2017 15:54

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