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Hillslope response to tectonic forcing in threshold landscapes

DiBiase, Roman A. and Heimsath, Arjun M. and Whipple, Kelin X. (2012) Hillslope response to tectonic forcing in threshold landscapes. Earth Surface Processes and Landforms, 37 (8). pp. 855-865. ISSN 0197-9337. doi:10.1002/esp.3205.

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Hillslopes are thought to poorly record tectonic signals in threshold landscapes. Numerous previous studies of steep landscapes suggest that large changes in long-term erosion rate lead to little change in mean hillslope angle, measured at coarse resolution. New LiDAR-derived topography data enables a finer examination of threshold hillslopes. Here we quantify hillslope response to tectonic forcing in a threshold landscape. To do so, we use an extensive cosmogenic beryllium-10 (^(10)Be)-based dataset of catchment-averaged erosion rates combined with a 500 km^2 LiDAR-derived 1 m digital elevation model to exploit a gradient of tectonic forcing and topographic relief in the San Gabriel Mountains, California. We also calibrate a new method of quantifying rock exposure from LiDAR-derived slope measurements using high-resolution panoramic photographs. Two distinct trends in hillslope behavior emerge: below catchment-mean slopes of 30°, modal slopes increase with mean slopes, slope distribution skewness decreases with increasing mean slope, and bedrock exposure is limited; above mean slopes of 30°, our rock exposure index increases strongly with mean slope, and the prevalence of angle-of-repose debris wedges keeps modal slopes near 37°, resulting in a positive relationship between slope distribution skewness and mean slope. We find that both mean slopes and rock exposure increase with erosion rate up to 1 mm/a, in contrast to previous work based on coarser topographic data. We also find that as erosion rates increase, the extent of the fluvial network decreases, while colluvial channels extend downstream, keeping the total drainage density similar across the range. Our results reveal important textural details lost in 10 or 30 m resolution digital elevation models of steep landscapes, and highlight the need for process-based studies of threshold hillslopes and colluvial channels.

Item Type:Article
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URLURL TypeDescription
DiBiase, Roman A.0000-0002-5347-8396
Whipple, Kelin X.0000-0002-8430-6925
Additional Information:© 2012 John Wiley & Sons, Ltd. Received 17 August 2011; Revised 4 January 2012; Accepted 9 January 2012. This work was supported by funding from the Geomorphology and Land Use Dynamics Program at NSF (EAR-0518998 to AMH, EAR-0724194 to KXWl. laser altimetry was acquired and processed by the National Center for Airborne Laser Mapping (NCALM) with support from Arizona State University (AMH, KXW), Caltech (Michael lamb), and the USGS. Taufique Mahmood helped develop the Rock Exposure Index. Comments by Dimitri Lague and an anonymous reviewer helped improve the manuscript.
Funding AgencyGrant Number
NSF Geomorphology and Land Use Dynamics ProgramEAR-0518998
NSF Geomorphology and Land Use Dynamics ProgramEAR-0724194
Arizona State UniversityUNSPECIFIED
Subject Keywords:threshold hillslopes; rock exposure; slope distributions; drainage density
Issue or Number:8
Record Number:CaltechAUTHORS:20120720-132036229
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Official Citation:DiBiase, R. A., Heimsath, A. M. and Whipple, K. X. (2012), Hillslope response to tectonic forcing in threshold landscapes. Earth Surf. Process. Landforms, 37: 855–865. doi: 10.1002/esp.3205
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32616
Deposited By: Jason Perez
Deposited On:23 Jul 2012 14:40
Last Modified:09 Nov 2021 21:28

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