Advance, Retreat, and Halt of Abrupt Gravel-Sand Transitions in Alluvial Rivers

Advance, Retreat, and Halt of Abrupt Gravel-Sand Transitions in Alluvial Rivers

Blom, A. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Chavarrias Borras, V. (TU Delft Rivers, Ports, Waterways and Dredging Engineering)
Ferguson, Robert I. (Durham University)
Viparelli, Enrica (University of South Carolina)

2017-10-16

Downstream fining of bed sediment in alluvial rivers is usually gradual, but often an abrupt decrease in characteristic grain size occurs from about 10 to 1 mm, i.e., a gravel-sand transition (GST) or gravel front. Here we present an analytical model of GST migration that explicitly accounts for gravel and sand transport and deposition in the gravel reach, sea level change, subsidence, and delta progradation. The model shows that even a limited gravel supply to a sand bed reach induces progradation of a gravel wedge and predicts the circumstances required for the gravel front to advance, retreat, and halt. Predicted modern GST migration rates agree well with measured data at Allt Dubhaig and the Fraser River, and the model qualitatively captures the behavior of other documented gravel fronts. The analysis shows that sea level change, subsidence, and delta progradation have a significant impact on the GST position in lowland rivers.

alluvial rivers
gravel bed rivers
gravel front
gravel-sand transition
mixed-size sediment
sand bed rivers

http://resolver.tudelft.nl/uuid:842174ef-df17-45ae-b558-6920b8171548

https://doi.org/10.1002/2017GL074231

2018-05-01

0094-8276

Geophysical Research Letters, 44 (19), 9751-9760

Institutional Repository

journal article

© 2017 A. Blom, V. Chavarrias Borras, Robert I. Ferguson, Enrica Viparelli