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Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools

Scheingross, Joel S. and Lamb, Michael P. (2016) Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools. Journal of Geophysical Research. Earth Surface, 121 (5). pp. 939-963. ISSN 2169-9003. http://resolver.caltech.edu/CaltechAUTHORS:20160930-130959510

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Abstract

Many waterfalls have deep plunge pools that are often partially or fully filled with sediment. Sediment fill may control plunge-pool bedrock erosion rates, partially determine habitat availability for aquatic organisms, and affect sediment routing and debris flow initiation. Currently, there exists no mechanistic model to describe sediment transport through waterfall plunge pools. Here we develop an analytical model to predict steady-state plunge-pool depth and sediment-transport capacity by combining existing jet theory with sediment transport mechanics. Our model predicts plunge-pool sediment-transport capacity increases with increasing river discharge, flow velocity, and waterfall drop height and decreases with increasing plunge-pool depth, radius, and grain size. We tested the model using flume experiments under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. The model and experiments show that through morphodynamic feedbacks, plunge pools aggrade to reach shallower equilibrium pool depths in response to increases in imposed sediment supply. Our theory for steady-state pool depth matches the experiments with an R^2 value of 0.8, with discrepancies likely due to model simplifications of the hydraulics and sediment transport. Analysis of 75 waterfalls suggests that the water depths in natural plunge pools are strongly influenced by upstream sediment supply, and our model provides a mass-conserving framework to predict sediment and water storage in waterfall plunge pools for sediment routing, habitat assessment, and bedrock erosion modeling.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2015JF003620DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2015JF003620/abstractPublisherArticle
ORCID:
AuthorORCID
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2016 American Geophysical Union. Received 26 MAY 2015; Accepted 11 MAR 2016; Published online 13 MAY 2016. Data presented in this paper, as well as a MATLAB code to calculate plunge-pool sediment-transport capacity, are available in the supporting information or by contacting J.S.S. We are grateful to Brian Fuller for assistance with laboratory experiments and benefitted from conversations with Jeff Prancevic, Andy Thompson, Patrick Sanan, Mike Gurnis, and Jeremy Venditti. Roman DiBiase and Chris Brennen assisted with waterfall surveys and, together with Kelin Whipple, kindly shared photographs and data from plunge pools in the San Gabriel Mountains. Greg Pasternack, two anonymous reviewers, Associate Editor Peter Ashmore, and Editor John Buffington provided constructive comments which improved the structure and presentation of this manuscript. We thank Mike Oxford and the U.S. Forest Service for access to the San Dimas Experimental Forest. We acknowledge funding from NSF (EAR-1147381) and NASA (12PGG120107) to M.P.L and a NSF Graduate Research Fellowship to J.S.S.
Funders:
Funding AgencyGrant Number
NSFEAR-1147381
NASA12PGG120107
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:sediment transport capacity; waterfalls; knickpoints; plunge pools
Record Number:CaltechAUTHORS:20160930-130959510
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160930-130959510
Official Citation:Scheingross, J. S., and M. P. Lamb (2016), Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools, J. Geophys. Res. Earth Surf., 121, 939–963, doi:10.1002/2015JF003620.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70697
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:30 Sep 2016 21:57
Last Modified:03 Nov 2016 20:05

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