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Pacific Southwest Research Station

 
Pacific Southwest
Research Station

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Publications and Products

Title: Measuring and modeling gravel transport at Caspar Creek, CA, to detect changes in sediment supply, storage, and transport efficiency

Authors: Richardson, P. W.; Wagenbrenner, J. W.; Sutherland, D. G.; Lisle, T. E.

Date: 2020

Source Water Resources Research. 56(6): e2019WR026389

Abstract:

We developed a technique for reconstructing annual gravel yields and generated a 55‐year record of gravel transport for the North Fork catchment of the Caspar Creek Experimental Watersheds in Northern California. The technique relies on field data collection including annual surveys of weir pond volumes and suspended sediment measurements, as well as an accounting for settling of suspended sediment and organic matter in the pond. We compared these annual yields to gravel yields predicted by the Wilcock two‐fraction bed load transport model, which we calibrated from measured values at Caspar Creek. We considered three velocity‐discharge relationships and found that values of hydraulic variables measured during storms produced the best fit between reconstructed and predicted annual gravel yields when years with large disturbances were excluded. We also compared predicted gravel transport rates to bed load transport rates measured from 1988 to 1995 with bed load pit samplers. We found that the calibrated model predictions agreed well with the field‐measured bed load transport rates. To investigate the role of supply and storage on gravel transport, we compared the reconstructed gravel yields to predicted gravel yields and found that increased occurrence of landslides and headcut erosion in the 1990s and early 2000s did not lead to an increase in gravel yields. Instead, input of large downed wood in the 1990s created storage space and decreased bed load delivery to the weir pond.

Keywords: Bed load transport, disturbance response, experimental watershed, monitoring

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Citation

    Richardson, P. W.; Wagenbrenner, J. W.; Sutherland, D. G.; Lisle, T. E. 2020. Measuring and modeling gravel transport at Caspar Creek, CA, to detect changes in sediment supply, storage, and transport efficiency. Water Resources Research. 56(6): e2019WR026389. https://doi.org/10.1029/2019WR026389.
Last Modified: August 14, 2020