MAPPING COASTAL EROSION HAZARDS AND INUNDATION ANTICIPATED FROM CLIMATE CHANGE IN MAINE

Dynamic sedimentary environments of coastal beaches and dunes requires repeated coastal mapping of shoreline change. Seasonal and interannual variability can only be understood through systematic monitoring and analysis. Routine monitoring is essential to capture both short-term changes induced by severe storms and long-term trends in erosion driven by negative coastal sediment budgets. Monitoring alone, however, is not sufficient for coastal management but instead must be incorporated with other physical features such as dune topography, the 100-year flood elevation, the seasonal berm width and volume, aspects of coastal engineering structures, distance of structures from the beach, etc. Dune geomorphology based on air photo interpretation and analysis of Lidar topography helps define the primary frontal dune, back dunes, tidal inlets, and coastal wetlands all subject to differing degrees of coastal hazards in the short term and due to ongoing and accelerating sea level rise. Using geological, topographical, hydrologic, and engineering aspects of the coastal beaches in Maine, the Maine Geological Survey has developed over a dozen data layers that are used in regulatory decision making, environmental restoration projects, coastal hazard mitigation decisions, and real estate decisions. Maps of regulated coastal dunes and erosion hazard areas are used in state policy that anticipates sea level rise of 2 feet by the year 2100 and increased coastal erosion. Weighted averages and statistical analysis of shoreline features has led to identification of the sections of shoreline currently most at risk of erosion. These data can then be used to weigh benefits and costs of dune restoration or beach nourishment. Inundation mapping in a geographic information system (GIS) is now being used to generate maps of a rise in the highest annual tide of 2 feet that simulate transgression of coastal wetlands into the upland. These maps and GIS data are now being made available for municipal use in shoreland zoning and comprehensive planning in anticipation of increased hazards from climate change. Through the use of these types of geologic maps, coastal towns are beginning to visualize and plan adaptation measures that will build coastal resiliency to today's storms and tomorrow's higher sea levels.