Hydrodynamic Controls on the Morphodynamic Evolution of Subaqueous Landforms

• Main Author: Nelson, Timothy L
• Format: Others
• Published: ScholarWorks@UNO 2017
• Subjects: sediment transport; numerical modeling; subaqueous shoals; barrier islands; Delft3d; Xbeach; Geology; Geomorphology
• Online Access: https://scholarworks.uno.edu/td/2425; https://scholarworks.uno.edu/cgi/viewcontent.cgi?article=3573&context=td

The southern Chandeleur Islands are an ideal setting to study shoal evolution given their history of submergence and re-emergence. Here, numerical models shed light on the attendant processes contributing to shoal recovery/reemergence following a destructive storm event. Simulations of a synthetic winter storm along a cross-shore profile using Xbeach shows that convergence of wave-induced sediment transport associated with repeated passage of cold-fronts initiates aggradation, but does not lead to reemergence. A Delft3d model of the entire island chain shows that as these landforms aggrade alongshore processes driven by incident wave refraction on the shoal platform, backbarrier circulation and resulting transport become increasingly important for continued aggradation and eventual emergence. Aggradation magnitudes are a function of depth ranging from 2 – 10 mm per event (onset to recovery to near mean sea level). In the absence of big storms, this modest aggradation can be more than one meter in a few years.