Author(s): David Gaeuman; Josh Boyce

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Abstract: The topographic relief associated with gravel bar morphology is critical for physical habitat diversity in gravel bed streams, as well as for a variety of ecological services ranging from temperature regulation to nutrient cycling. This paper describes the topographic responses of a reach of the Trinity River in California, USA, to multiple dam-regulated flow releases, repeated gravel augmentations, and changes in the gravel fluxes delivered from upstream. Changes in the bed elevations and bed relief are quantified with metrics extracted from detailed topographic surveys conducted over a 7-year time span, and gravel fluxes into and out of the study areas are computed from a gravel budget based on topographically-determined changes in gravel storage and sampled bedload transport rates. The results show that flow and gravel management increased bed relief and the availability of one type of physical habitat over the first 6 years of the study period, but decreased bed relief and habitat availability in the final year of the study period. The switch to decreasing bed relief appears to be linked to a large increase in the gravel supply to the reach that produced widespread aggradation in pools and thalweg areas. Our results support the hypothesis that maximum bed relief and high levels of physical habitat diversity are associated with intermediate bed material supply rates.

DOI:

Year: 2018