Modeling temporal trends in bedload transport in gravel-bed streams using hierarchical mixed-effects models

Hassan, Marwan A., Robinson, Samuel V.J., Voepel, Hal, Lewis, Jack and Lisle, Thomas E. (2014) Modeling temporal trends in bedload transport in gravel-bed streams using hierarchical mixed-effects models. Geomorphology, 219, 260-269. (doi:10.1016/j.geomorph.2014.05.019).

Abstract

In this paper, we used a bedload transport data set collected at North Fork Caspar Creek, California, to examine temporal variation in sediment transport rate over a 7-year period. Using a hierarchical mixed-effects model, we examined across and within-event variation to determine whether the bedload–shear stress relation trends over time. The relation between bedload transport and shear stress was modeled using log(Qb) = a + B*log(T) + E, where a and B are constants and E is an error term. Depending on the length of observation, a and B can vary over several orders of magnitude, making modeling of transport based on flow challenging and highly inaccurate. We found a higher order yearly relation between bedload and shear stress, indicating systematic changes to the system over time. In the absence of significant additions to the system, a decreases roughly linearly over time, while B does not show any trend. From the systematic decline in a, we infer changes to sediment availability in the stream over time. Mixed-effects models have the potential to be a useful predictive tool in fluvial geomorphology, as they are more powerful at detecting trends in sediment transport rates than individual linear regressions.

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Contributors

Author: Hal Voepel

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