1. Morphological signature of gully development by rapid slide retrogression in a layered coarse-grained delta foreslope
- Author
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Locat, Jacques, Azizian, Ali, Stronach, Jim, Hospital, Aurélien, Young, Chris, Turmel, Dominique, and Bevan, Andrew
- Abstract
Coarse-grained deltas are often characterized by steep foreslopes (often more than 10°) that are traversed by delta-front channels. The channels thus erode into relatively steeply inclined bedding. In this context, the slopes flanking the channels can be steeper than the friction angle since they include a component of dip related to the delta-front slope as well as the channel-related erosion slope. In this study, part of the Busu River delta (Papua New Guinea) was imaged using a high-resolution multibeam bathymetry survey over an area where the angle of the slopes flanking the channels locally reaches 50°. A detailed analysis of the delta slope morphology has revealed an additional source of instability due to erosion within the main channels. In some places, erosion cuts into the channel flank forming a local knickpoint inclined in a direction approaching that of the bed dip. The cut can then initiate breaching or static liquefaction failure from that point up to the crest of the interfluve resulting in a V-shaped gully.
- Published
- 2020
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