Coastline Mapping and Identification of Erosion Hazard Areas

Management Agency (FEMA) conduct a statistically valid number of case studies to determine the feasibility of mapping erosion hazard areas in the United States coastal zone. FEMA funded the Washington State Department of Ecology to conduct one of these case studies in Pacific County. Pacific County is located north of the Columbia River and includes about 60 km of ocean shoreline. The overall objectives of the study were to map the current shoreline, calculated change rates, and project and plot the 60-year erosion hazard area with existing information from FEMA's Flood Insurance Rate Maps. In this paper the methods used to calculate these shoreline change rates are described. During the study it was determined that about 626 structures larger than 5 by 5 m were within the projected 60-year (2055), 100 year flood zone. During the 1950 era to 1995 period rates of change within the County varied from 28.3 m/year of accretion to erosion of 27.0 m/year, with a mean rate of 0.9 m/year of accretion