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Autogenic entrenchment patterns and terraces due to coupling with lateral erosion in incising alluvial channels

Malatesta, Luca C. and Prancevic, Jeffrey P. and Avouac, Jean-Philippe (2017) Autogenic entrenchment patterns and terraces due to coupling with lateral erosion in incising alluvial channels. Journal of Geophysical Research. Earth Surface, 122 (1). pp. 335-355. ISSN 2169-9003. http://resolver.caltech.edu/CaltechAUTHORS:20161004-094902569

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Abstract

The abandonment of terraces in incising alluvial rivers can be used to infer tectonic and climatic histories. A river incising into alluvium erodes both vertically and laterally as it abandons fill-cut terraces. We argue that the input of sediment from the valley walls during entrenchment can alter the incision dynamics of a stream by promoting vertical incision over lateral erosion. Using a numerical model, we investigate how valley wall feedbacks may affect incision rates and terrace abandonment as the channel becomes progressively more entrenched in its valley. We postulate that erosion of taller valley walls delivers large pulses of sediment to the incising channel, potentially overwhelming the local sediment transport capacity. Based on field observations, we propose that these pulses of sediment can form talus piles that shield the valley wall from subsequent erosion and potentially force progressive channel narrowing. Our model shows that this positive feedback mechanism can enhance vertical incision relative to 1-D predictions that ignore lateral erosion. We find that incision is most significantly enhanced when sediment transport rates are low relative to the typical volume of material collapsed from the valley walls. The model also shows a systematic erosion of the youngest terraces when river incision slows down. The autogenic entrenchment due to lateral feedbacks with valley walls should be taken into account in the interpretation of complex-response terraces.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2015JF003797DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2015JF003797/fullPublisherArticle
ORCID:
AuthorORCID
Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 2016 American Geophysical Union. Received 21 NOV 2015; Accepted 29 SEP 2016; Accepted article online 4 OCT 2016; Published online 25 JAN 2017. This manuscript has greatly benefited from the remarkably thorough and precise comments of the Editor John Buffington and from insightful and engaging reviews from Frank Pazzaglia and an anonymous reviewer. We also thank Michael Lamb for his comments. This study is partly supported by a PRF New Direction grant of the American Chemical Society (grant PRF 53814-ND8), a Doc.Mobility fellowship of the Swiss National Foundation (project P1SKP2_158716) for Malatesta, NSF grant EAR-1349115 (to Michael Lamb) for Prancevic, and the donors of the American Chemical Society Petroleum Research Fund (to Michael Lamb). The source code of the model is publicly available on the web platform of the Community Surface Dynamics Modeling System (http://csdms.colorado.edu).
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
American Chemical Society Petroleum Research Fund53814-ND8
Swiss National Foundation (SNF)P1SKP2_158716
NSFEAR-1349115
Subject Keywords:terrace; autogenic; entrenchment; fill-cut
Record Number:CaltechAUTHORS:20161004-094902569
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20161004-094902569
Official Citation:Malatesta, L. C., J. P. Prancevic, and J.-P. Avouac (2017), Autogenic entrenchment patterns and terraces due to coupling with lateral erosion in incising alluvial channels, J. Geophys. Res. Earth Surf., 122, 335–355, doi:10.1002/2015JF003797
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70806
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Oct 2016 18:11
Last Modified:07 Jul 2017 22:15

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