Date of Award

2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Ocean Engineering

Department

Ocean Engineering

First Advisor

M. Reza Hashemi

Abstract

Tropical cyclones - also called hurricanes and typhoons - result in major damage and fatalities around the world almost every year due to the massive coastal and inland flooding. Integrating coastal and inland regional flooding models as well as assessing the impacts of climate change helps better understand the overall risk of a hurricane at the present and in the future. Coastal flooding causes damages to the coastal structures. While regional models are not capable of accurately predicting the damage to the coastal structures, the high-fidelity computational fluid dynamics (CFD) models can be implemented to simulate the flow properties around the coastal structures. These CFD models should be forced by regional models due to their high computational cost. This dissertation tries to address some knowledge gaps in the literature with regard to coastal flood risk using both numerical and experimental techniques. In particular, compound coastal-inland flooding, climate change and sea level rise, and multi-scale numerical modeling have been focused.

In the first manuscript of this dissertation, the impacts of a number of factors (reservoirs, historical textile mill dams, and bridges) on the severity of a record-braking flood within a watershed in the New England, Pawtuxet River, were assessed. These factors are currently omitted within the risk assessments tools such as flood insurance rate maps. Further, to better understand possible future risks in a warmer climate, an extreme flood event under a synthetic wet hurricane was simulated. It was shown that this hurricane can generate a flooding equivalent to a 500-yr event in this watershed. Further research is necessary to develop the integrated coastal and inland flood models that are forced by a single atmospheric model.

In the second manuscript, the impact of sea level rise (SLR) to estimate the water elevation in the regional storm surge models was studied using two methods. The linear method superimposes the SLR linearly to the estimated water elevations while the nonlinear method uses a new model with updated data to include the impact of SLR. A simplified theoretical formulation, a number of idealized cases, and two real case studies were assessed to compare the linear and nonlinear methods. In general, based on the results of the idealized and real studies, a discrepancy of up to 10 % between the linear and nonlinear approaches is expected in estimation of maximum water elevation. Further research is necessary to investigate the effect of SLR and climate change on the boundary forcing of regional storm surge models.

Finally, in the third manuscript, to better understand the flood risk around an array of buildings during coastal storms, the impacts of waves and combined wave-currents on a tandem configuration of two model structures in the scale of 1:100 were assessed using the experimental and numerical methods. Smoothed Particle Hydrodynamics (SPH) technique was implemented for the numerical simulation, and the experimental data was used to validate this model and observe the flow field. Results showed that SPH can do a good job in prediction of wave-current interaction in the flume. It was shown that the forces exerted on the aft structure decreased when it was located equal to its size apart from the forward structure; then, forces increased when the aft structure was shifted away from the forward structure. Numerical simulation of the waves in the presence of the following current showed that forces exerted on the forward and aft structures increased 18 % and 3 %, respectively, compared to those in the absence of currents.

Further research is necessary to examine a variety of buildings configurations and how the array configuration affects the flood forces.

Available for download on Friday, May 13, 2022

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