News & Events

Noon seminar - How do waves shape deltas?

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


Andrew Ashton

Woods Hole Oceanographic Institution


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.