all aspects of storms and their impact has been a fundamental objective of 

 coastal research. Unfortunately, the understanding of sediment transport and 

 beach erosion lags behind the capability to predict the waves and flooding 

 which may occur during a storm event. 



3. The National Flood Insurance Program, which insures property 

 located within coastal and inland flood-prone areas, is based on the expected 

 flood levels associated with a storm with a 1 percent probability of 

 occurring per year (a 100-year storm). Wave heights are considered, but 

 there is no official procedure to treat flooding resulting from either 

 long-term erosion or from the erosion associated with the 100-year storm. 

 Although this may be a reasonable assumption for riverine flooding, it is not 

 appropriate along the coast where the shoreline is constantly evolving. 



Purpose 



4. In December 1985, the Federal Emergency Management Agency (FEMA) , 

 which manages the National Flood Insurance Program, requested that the US 

 Army Engineer Waterways Experiment Station's (WES's) Coastal Engineering 

 Research Center (CERC) conduct a 6-month study to examine the feasibility of 

 accounting for the processes of erosion and overwash in determining coastal 

 high-hazard flood zones along the Atlantic and Gulf coasts. Specifically, 

 this report addresses methods for determining variations in the width of the 

 velocity (V-) zone, as defined by FEMA, which would occur if these processes 

 could be quantitatively estimated. 



5. At present, an area is designated a V-zone only if the maximum 

 water level associated with the 100-year storm would support a 3 ft-high 

 (0.9 m) wave. In areas where dunes exist, if the dune height exceeds the 

 water level, the dune and inland zones are assumed to be "protected," and the 

 V-zone is topographically mapped only to the intersection of the water level 

 with the dune. That the dune may erode or that an area is historically prone 

 to flooding during storms is considered only by subjective means. 



6. The fundamental question to be addressed is, "Will a particular 

 dune survive the 100-year event?" Specific details as to how the dune 

 survives (or erodes) are not required. At one extreme (the present FEMA 

 procedure), the dunes can be treated as fixed barriers, resulting in narrow 

 V-zones; at the other extreme, the existence of dunes can be ignored, 



