Quantifying the Role of Wetlands
in Coastal Resilience

An Environmental Communications Research Internship
March 17, 2017
Engaging Residents in Resilience
March 29, 2017

The following blog post is by Ali Rezaie, a doctoral student at George Mason University working to understand and evaluate how ecosystem services enhance the resilience of coastal communities. 

Virginia Sea Grant supports Rezaie through a Program Development grant to advance his graduate research.

Since the inception of my research career, I have been working on understanding coastal processes, and striving to provide further insights on coastal resilience. Most of my work has involved applying numerical models to better explain complex coastal physical processes, and improve the management of coastal ecosystem services. Modeling coastal flooding due to tides, surge, and waves, developed my interest in applying the results for societal welfare, especially to build resilient coasts which are vulnerable with changing climate and rising seas.

When I first started graduate school at the George Mason University (GMU), I worked on coastal hydrodynamic and wave models to evaluate current flooding conditions due to historical storms in areas near the Chesapeake Bay. Results from the models show that nearshore regions and areas near the bay can experience a maximum flood elevation ranging from 1.5 to 6ft (0.5-2m). In addition, recurrent flooding due to storm surge in coastal areas of the United States is expected to increase with changing climate, and sea level rise (SLR), and financial losses from hurricanes are likely to increase with development and growing populations. In addition, the increasing rate of SLR will alter coastal wetland dynamics, submerging wetlands and causing them to move landward.

For these reasons, I aimed to prepare an estimate of how future inundation could change with rising seas and moving marshes. Analyzing the NOAA predictions, I found out that with 6 ft. (1.83 meter) rise in sea level, the total estuarine wetland in Virginia and Maryland will be reduced by up to 86 percent, and 88 percent respectively. Incorporating the projected local SLR, and respective marsh migration in the models, I simulated the flood inundation for a set of low to high intensity storms. A comparison of the flooding extent for current and future scenarios suggests that for strong hurricanes, total flooded area could increase by up to 116 percent, and 78 percent in the coastal counties of these states. On the other hand, previous studies suggested that wetlands can attenuate the impact of storm surge by reducing wave energy, erosion and currents velocity, and the ecosystem services provided by wetlands are likely to become more valuable as they become more threatened.

That prompted me to look for opportunities to work with Dr. Margaret Walls, a senior fellow at the environmental policy think tank, Resources for the Future (RFF) in Washington, D.C. The work involved integrating my modeling results with economic analysis to develop an analytical framework to quantify the protective value of natural, and nature-based features such as coastal wetlands. Simultaneously, my focus included outlining an estimate of future inundation extent, and damage by storm surge, SLR and marsh migration that would address the vulnerability of coastal areas due to flooding. This also involved rigorous work on computational models, collecting relevant hydrodynamic, atmospheric, and land use data. Under the supervision of my PhD Supervisor, Dr. Celso Ferreira, Assistant Professor in Civil Infrastructure and Environmental Engineering department at GMU, I applied high resolution coastal storm surge, and wave models to compute the extent and depth of flooding due to hurricanes of difference intensities. We simulated the inundation for five historical hurricanes with two scenarios—one scenario uses the land cover in place at the time of the hurricane, and a counterfactual simulation in which all wetlands in our study region are replaced with bare land.

To estimate the dollar value of the services wetlands provide, we combined parcel-level residential property values with flood depth-damage functions; the difference in damages between the two simulations is our estimate of the value of the protective service provided by wetlands. We found wetlands in the Chesapeake Bay region provided protective services in all five of the hurricanes we analyzed, ranging in value from $55 to $454 million. The value is highest for the worst hurricanes, meaning that wetlands may become increasingly valuable with climate change and sea level rise. Furthermore, preliminary damage estimation indicates the property damage in Maryland alone can rise up to $1150 million under the projected SLR and marsh migration.

I have presented some of the results at conferences, such as in the 2016 American Shore and Beach Preservation Association National Coastal Conference, and American Geophysical Union (AGU) Fall 2016 meeting. During the AGU meeting, academics from multiple disciplines expressed genuine interest, and provided valuable remarks on how the research will help coastal landscape development, and climate adaptation plans. While the work can contribute to coastal resilience and policymaking, combining an economic perspective that focuses on better allocation of resources and human perception, with state of the art surge and wave modeling is always challenging.

The work has allowed me to build cross-disciplinary understanding on issues related to coastal hazards and resilience. Also, working part time as a visiting scholar at RFF I am developing my multi-disciplinary research skills, and expanding my area of expertise that could be applied on a broader range of coastal sustainability. Together with Dr. Walls, and Dr. Ferreira, currently we are expanding the framework with statistical analysis of modeling results, and incorporating field data measurement to improve the quantification of wetland protective services in the Chesapeake Bay regions. Finally, as a team we plan to disseminate our research outcomes in conferences of multiple disciplines, open access journal publications, and through the George Mason University Flood Hazard Research Lab website.

By Ali Rezaie

For queries and suggestions, please contact the writer at arezaie@gmu.edu or rezaie@rff.org. Previous presentations and poster can be found at https://gmu.academia.edu/AliMohammadRezaie.