Speaker: Celso Ferreira, George Mason University
Title: Hurricane storm surge and waves attenuation by nature-based coastal defenses in the Chesapeake Bay
Abstract: Hurricane Sandy demonstrated the vulnerability of the East Coast to extreme events causing wide spread damage and highlighting the need for resilient coastal defenses. The potential of natural wetlands to attenuate storm surge and dampen wave energy has been investigated in many laboratory and numerical studies, however fewer field experiments exist to validate or quantify these processes in a natural environment. Current research indicates that the capacity of wetlands to attenuate storm surge and waves is highly dependent not only on spatial scales but also seasonally dependent vegetation biomechanics, micro-topography, groundwater levels and storm characteristics. We are currently performing a 2-year field campaign to investigate storm surge and wave attenuation in 4 protected areas in the Chesapeake Bay. Our study sites range from lower bay areas with semi-direct contact to the ocean (Eastern Shore of Virginia Wildlife Refuge), mid-bay areas (Dameron Marsh Natural Area Reserve) and upper bay areas in the tidal Potomac. Pressure transducers and Acoustic Doppler Current Profilers (ADCPs) have been permanently deployed to capture time series of water depths and vertical velocity gradients. In collaboration with partners from the United States Geological Survey (USGS), investigations of vegetation characteristics (height, diameter, and stem density) are conducted to allow for improved understanding of the factors contributing to flow-resistance. Additionally, high resolution topo-bathymetric surveys are been conducted to map the complex geomorphology of these areas. The field data set is used to calculate rates of attenuation across marsh transects, and supports a regional storm surge model calibration for an accurate parameterization of coastal wetland vegetation on a regional scale. For this study, storm surge was modeled along the Virginia portion of the Delmarva Peninsula to improve our understanding of the sensitivity of simulated storm surge in these environments to: 1) bottom friction due to wetlands parametrization; 2) bathymetric uncertainty; 3) uniformity of shallow channels; and 4) barrier island connectivity. The coupled hydrodynamic-wave model (ADCIRC+SWAN) was used for this study along with a numerical mesh adapted from the FEMA region III grid. In the adapted mesh, resolution was increased in areas of interest from 30-100m in the FEMA mesh to 10-30 m for this study. Here we also take advantage of a recently developed domain decomposition approach to improve model efficiency and evaluate multiple scenarios while minimizing computational expenses. Hurricane hindcasts and synthetic storms were used to evaluate model sensitivity to friction, topo-bathymetry and configuration. Initial results indicate water level dependency highly correlated to inlet conditions at barrier islands and topographic features of the marsh system within the Back Bay. Results from this study will improve the ability of decision makers to evaluate the value of marsh systems for coastal defense considerations and to improve understanding of the hydrodynamic interaction of barrier island-back bay systems and storm-surge.
Bio: Dr. Celso Ferreira is currently a visiting scholar at Stanford University. He is an Assistant Professor of Water Resources Engineering in the Civil, Infrastructure and Environmental Engineering Department of George Mason University. He is also an Associate Researcher at the USGS National Research Program in Reston, VA. He has a PhD from Texas A&M University in Civil Engineering with a focus on Water Resources Engineering. He has a ME in Hydrology from the CEDEX Institute in Spain, a MS in Environmental Engineering and a BS in Civil Engineering from the Federal University of Santa Catarina in Brazil. His current research interests are associated to water related extreme weather hazards and its impacts to civil engineering infrastructure. His research is currently funded by the National Science Foundation (NSF), the Department of Interior (DOI), the National Fish and Wildlife Foundation (NFWF) and several private organizations. His research group is currently investigating the potential of nature to reduce hurricane flooding impacts to critical infrastructure. His research also strive to incorporate climate variability and human induced environmental changes to engineering practice by considering climate change, sea-level rise, urbanization and environmental degradation impacts on engineering design. His work ranges across spatial scales and the projects range from international to regional and local applications.