Date of Award

Spring 2024

Document Type


Degree Name

Doctor of Philosophy (PhD)


Civil & Environmental Engineering

Committee Director

Xixi Wang

Committee Member

Dalya Ismael

Committee Member

Mujde Erten-Unal


This dissertation examines and presents mechanisms of flooding in a low-gradient coastal watershed, located in Virginia Beach, Virginia, USA. The watershed comprises the North Landing River watershed and the West Neck Creek watershed, both characterized by a low topographic gradient. The analysis relied on examining simulations generated using one-dimensional and two-dimensional HEC-RAS models. These models were developed using a 1-m digital elevation model (DEM) obtained from the U.S. Geological Survey (USGS). To calibrate and validate the models, unsteady flows resulting from historical hurricanes (e.g., Matthew, Sandy, and Isabel), southern winds, and/or rising sea levels were utilized. Some flows were caused by one of these three forces, whereas others might have been generated by two or three forces simultaneously. Subsequently, the models were used to predict water surface elevations for a variety of scenarios to assess possible flooding based on the current terrains. The predictions were examined in the form of cross-sectional profiles, water surface elevation (WSE) profiles, and depth and velocity graphs. While the HEC-RAS models might have some limitations in mimicking the impact of historical events, they were deemed sufficient for understanding and reproducing the impacts of the aforementioned three forces. Additionally, several engineering measures for flood mitigation were proposed and simulated using the HEC-RAS models. The results showed that the proposed mitigation measures be effective for the low-gradient watershed. Moreover, the proposed mitigation measures were predicted to reduce fluctuations in WSE, flow velocity, and flood depth compared to those under existing conditions.


In Copyright. URI: This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).