Document Type

Article

Journal/Book Title/Conference

Journal of Geophysical Research: Earth Surface

Volume

123

Issue

8

Publisher

AGU

Publication Date

8-20-2018

Keywords

Sediment transport, sediment wave, sediment supply, grain size, discharge, dam

First Page

1879

Last Page

1909

DOI

https://doi.org/10.1029/2017JF004534

Abstract

Temporal and spatial nonuniformity in supplies of water and sand in a river network leads to sand transport that is in local disequilibrium with the upstream sand supply. In such river networks, sand is transported downstream as elongating waves in which coupled changes in grain size and transport occur. Depending on the magnitude of each sand-supplying event and the interval between such events, changes in bed-sand grain size associated with sand-wave passage may more strongly regulate sand transport than do changes in water discharge. When sand transport is controlled more by episodic resupply of sand than by discharge, upstream dam construction may exacerbate or mitigate sand-transport disequilibria, thus leading to complicated and difficult-to-predict patterns of deposition and erosion. We analyzed all historical sediment-transport data and embarked on a 4-year program of continuous sediment-transport measurements to describe disequilibrium sand transport in a river network. Results indicate that sand transport in long river segments can evolve over ≥50-year timescales following rare large sand-supplying events. These natural changes in sand transport in distal downstream river segments can be larger than those caused by an upstream dam. Because there is no way to know a priori whether sand transport in a river has changed in response to changes in the upstream sand supply, contemporary continuous measurements of sand transport are required for accurate sand loads and budgeting. Analysis of only historical sediment-transport measurements, as is common in the literature, may lead to incorrect conclusions with respect to current or future sediment-transport conditions.

Available for download on Wednesday, February 20, 2019

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