Physical controls on salmon redd site selection in restored reaches of a gravel-bed river
Abstract
Large-scale river restoration programs have emerged recently as a tool for improving spawning habitat for native salmonids in highly altered river ecosystems. Few studies have quantified how habitat features of varying scale influence redd site selection in restored channels, which is needed to guide restoration planning. We investigated Chinook salmon spawning site utilization, and measured and modeled habitat characteristics over a range of spatial scales in two restored reaches of a gravel-bed river. At the grain scale, we observed salmon redd construction in coarse, gravel substrates located in areas of high sediment mobility, as determined by measurements of gravel friction angles and a grain entrainment model. At the micro-habitat scale, modeled habitat quality and hyporheic flow were strong predictors of redd occurrence, though the relative roles of these variables differed between sites. At the geomorphic-unit scale, salmon redds were located near transitions between pool-riffle bedforms, in regions of high predicted intragravel flows. Our findings indicate that the physical controls influencing salmon redd site selection in two restored river channels were similar to results reported for natural channels elsewhere. Our results further highlight the importance of quantifying flow-sediment-biota interactions across spatial scales, which is required to fully understand ecological benefits provided by river restoration projects.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP41C2332H
- Keywords:
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- 0442 Estuarine and nearshore processes;
- BIOGEOSCIENCES;
- 0481 Restoration;
- BIOGEOSCIENCES;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY