ASSESSING COASTAL EROSION HAZARD VULNERABILITY IN CONNECTICUT

Over 2 million people live in shoreline towns and cities in Connecticut. The current USGS Coastal Vulnerability Index ranks the entire Connecticut coast as having a low risk to erosion, yet large areas in the state have experienced significant erosion during 20^th and 21^st century hurricanes. In this study, we assess coastal erosion hazard in Connecticut in fine detail by incorporating high resolution datasets for geomorphology, coastal slope, historic rates of erosion/accretion, and mean tide range. Specific datasets we use in our analysis include: 1) the NOAA Environmental Sensitivity Index, which classifies the current shoreline interface according to grain size and vegetation type; 2) CT State surficial materials maps and soil maps, compiled at 1:24,000 and 1:12,000, respectively; 3) 1 m LiDAR DEMs of 2006 and 2012; and 4) the NOAA/CT DEEP/UConn Shoreline Change Project, which assessed shoreline erosion and accretion using survey maps and aerial photographs from 1880-2006. From preliminary investigation we have determined that the shoreline vulnerability is more complex than previous studies have shown. Important variations exists for the material exposed along the coast and in coastal landforms in general, such as manmade structures, bedrock outcrops, glacial deposits varying from sand to boulders, sand dunes and salt marshes. To help characterize these variations we reclassified the Environmental Sensitivity Index and surficial deposits in ArcGIS and expanded the ranking system for resistance to erosion. The ranking we use is 1-5, adapted from the USGS Coastal Vulnerability Index with expanded geomorphology definitions applicable to the CT coast. Geomorphic vulnerability is mostly 3-5 distinguished by rocky more resistant areas of low vulnerability and sandy, more highly vulnerable areas. LiDAR based topography and slope analysis provide high resolution coastal slope rankings for the shoreline. Combining these new rankings produces a detailed assessment, and provides an improved definition of geographic and geologic factors dominating coastal erosion vulnerability in Connecticut.