RENCI: FEMA Region III Coastal Floodplain Inundation Study

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FEMA Region III Coastal Floodplain Inundation Study


As part of the Federal Emergency Management Agency's Floodplain Modernization Program, a partnership has been assembled to develop a state-of-the-art system to compute storm surge elevations FEMA Region III coastal waters for floodplain analysis, as required by FEMA.   Experts in the fields of coastal storm surge, wind-driven waves, Geospatial Information Systems, and high-performance computational systems are working together in this effort to establish new base flood elevations.  The project partners include:  US Army Corps of Engineers Duck Field Research Facility, Renaissance Computing Institute (RENCI), ARCADIS, Ocean Weather Inc, UNC-Chapel Hill Institute of Marine Sciences, Applied Research Associates/IntraRisk, and Dewberry and Davis.

The overall approach has been to assemble the pieces of system to enable the computation of still water levels using recent developments in similar projects (e.g., North Carolina Floodplain Mapping Program, Louisiana Coastal Protection and Restoration/FEMA).  The primary components include assembly of a state-of-the-art Digital Elevation Model (DEM) that merges the latest LIDAR surveys of FEMA Region III coastal counties and available bathymetric data sets, from which the numerical model grid topography and bathymetry are derived; advanced numerical models for storm surge, oceanic and near-shore wave fields, and tropical cyclone wind fields are combined into a flexible software framework on RENCI's high-performance computer systems; development of the necessary hurricane parameter representations through application of the Joint Probability Method (JPM); and post-processing statistical methods for derivation of return periods from the computational results and JPM statistics.  This document describes the development of the DEM and vertical datum analysis, numerical model grid generation, tropical cyclone statistical development, and archival strategy of the computational results.


Last Updated ( Tuesday, 08 March 2011 16:47 )

Letter from FEMA

The Federal Emergency Management Agency has initiated a study to update the coastal storm surge analysis within the states of Virginia, Maryland, and Delaware, and the District of Columbia including the Atlantic Ocean, Chesapeake Bay and its tributaries, and the Delaware Bay.  The study will replace outdated coastal storm surge stillwater elevations for all Flood Insurance Studies in the study area, and serve as the basis for new coastal hazard analysis and ultimately updated Flood Insurance Rate Maps (FIRMs).  Study efforts were initiated in August of 2008, and are expected to wrap up in the spring of 2010.  A plan is presently being formulated to prioritize study areas for updated coastal hazard mapping and FIRMs, which will commence subsequent to the completion of the study.  

The storm surge study will utilize the Advanced Circulation Model for Oceanic, Coastal and Estuarine Waters (ADCIRC) for simulation of 2-dimensional hydraulics.  The ADCIRC model will be coupled to 2-dimensional wave models to calculate the combined effects of surge and wind-induced waves.  Models will be developed to provide a representative terrain surface throughout the study area.  Topographic elevations will be based on the best available data across the region, including LiDAR data where available.  Model refinement will be tailored to ensure sufficient resolution of features affecting surge propagation within the coastal floodplain, such as rivers, tidal channels, dunes, etc.    Model performance will be calibrated using tidal simulations and then validated by comparing surge simulations against measured historical events such as Hurricane Isabel.  

Both tropical and extra-tropical storms will be simulated for determination of return period storm surge elevations.  The historical record of events in the region will be used to develop a synthetic suite of storm tracks and associated wind and pressure fields to drive the models.  This will provide a full population of storm surge response data across the study area.  The Joint Probability Method approach will be used for statistical analysis of the tropical storm surge return period elevations, whereas the Empirical Simulation Technique (EST) will be used to determine extra-tropical storm surge return period elevations.  Final return period elevations will be determined at the 10%, 2%, 1% and 0.2% annual chance floods. 

At the conclusion of the study, a series of public meetings will be held to facilitate presentation and discussion of results and future plans for updating FIRMs within FEMA Region III.   Preliminary meeting locations are identified as Dover and Rehoboth Beach Delaware, Ocean City, Baltimore and Annapolis Maryland, Washington D.C., Richmond, Virginia Beach, Norfolk/Portsmouth, and Hampton Roads/Newport News Virginia.  

This information is being distributed to Federal and State-level stakeholders in Virginia, Maryland, the District of Columbia, and Delaware.  Federal Agencies include the U.S. Army Corps of Engineers District Offices in Philadelphia, Baltimore and Norfolk, U.S. Geologic Survey State Water Science Centers and the National Oceanic and Atmospheric Administration.  State Agencies include the floodplain management, coastal zone management, and emergency management offices.  Please distribute this information to organizations, communities and individuals as you see fit.

Study updates, results, and public meeting locations and dates will be periodically distributed via email.  If you would like to receive these updates or have any questions, please contact Ms. Robin Danforth, FEMA Region III at This e-mail address is being protected from spambots. You need JavaScript enabled to view it or at (215) 931-5573.  


Eugene K. Gruber, Director
Mitigation Division
Last Updated ( Tuesday, 12 January 2010 17:40 )



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