News & Events

Noon seminar - How do waves shape deltas?

Monday, September 20, 2010, 12:00PM - 1:00PM

Speaker

Andrew Ashton

Woods Hole Oceanographic Institution

Location:

ARC 620

The mark of ocean waves on the depositional pattern of river deltas tends to be clear, creating characteristic landforms such as beach ridges or even downdrift-extending spits. Many wave-dominated deltas, however, exhibit plan-view asymmetry including the formation of discrete breaks in shoreline orientation and the development of spits and migrating shoreline sandwaves along the downdrift flank. A numerical model of plan-view shoreline evolution demonstrates how the angle distribution of incoming waves can have a first-order effect delta evolution, leading to asymmetrical development observed in nature. Furthermore, because the shape of a wave-influenced delta arises as a feedback between the sediment delivery rate of the river and alongshore sediment transport, the actual littoral transport of sediment away from a river mouth will typically be less than the maximum potential sediment transport for a given wave climate. The characteristics of both incoming wave and direction can be used to provide a measure to estimate whether a delta would be fluvially or littorally dominated.