Date of Award

Summer 8-17-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Advisor

Jean D. MacRae

Second Committee Member

Bryan Pearce

Third Committee Member

Chris Massey

Additional Committee Members

Huijie Xue

Damian C. Brady

Abstract

Elevated water level and large waves cause extensive damage and economic loss to coastal communities. An integrated atmosphere-ocean-coast modeling system that links physical processes with scales ranging from the open ocean to the surf zone has been developed for the Gulf of Maine. The modeling system includes a hydrodynamic model, a wave overtopping model and a sediment transport model. It is then applied to investigate and gain a comprehensive understanding of the following coastal processes: (1) the interaction between tide-surge, waves and bathymetry, (2) coastal flooding due to wave overtopping, and (3) sand transport.

Both coastal flooding and sand transport rely on the accurate prediction of water level, waves, and currents at the coast. This work has demonstrated that the interactions between tide-surge, waves and bathymetry have a significant impact on coastal waves, circulation and water level; and the interactions exhibit strong temporal and spatial variability along the coast. The inclusion and appropriate representation of the interaction processes in numerical modeling is important for coastlines with complex configurations.

The integrated modeling system has been applied to predict coastal flooding due to wave overtopping at the seawall in Scituate, Massachusetts. The capacity of the seawalls to protect coastal communities against flooding as sea level rises is investigated. It has been shown that seawalls will have to be elevated much more than the projected sea level rise to cope with future storms due to the presence of larger waves approaching the coast as depth increases.

Sand transport and its response to different storm characteristics are closely linked to waves and currents. Local bathymetry and winds are the two most important factors determining waves, currents and sand transport. The role of wind-driven and wave-induced current for sand transport varies depending on water depth and coastline geometry. The wind-driven current dominates in shallow water, while the wave-induced current is more significant at headlands and around coastal structures and islands. Differences in net sand transport mainly result from different flow patterns due to the counterbalance between wind-driven and wave-induced currents.

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