Dam effects on bedload transport on the upper Santa Ana River, California, and implications for native fish habitat

River Research and Applications
By:  and 

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Abstract

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Dam effects on bedload transport on the upper Santa Ana River, California, and implications for native fish habitat
Series title River Research and Applications
DOI 10.1002/rra.3443
Year Published 2019
Language English
Publisher Wiley
Contributing office(s) California Water Science Center
Description 14 p.
First page 1
Last page 14
Country United States
State California