A GIS ANALYSIS OF COASTAL BLUFF EROSION IN MAINE

Bluffs of glacigenic sediment exist along 53% of the tidal shoreline of Maine. Under the current regime of rising sea level, waves, groundwater, and subaerial processes easily erode these materials. The hazardous nature of the bluffs is not widely recognized by the public, and new homeowners are often shocked to find out that their property is disappearing. To better educate the public, the Maine Geological Survey is mapping the stability of the coastal bluffs. This report utilizes that database along with other available data to determine what controls the relative stability of the bluffs.

A geographic information system (GIS) was used to relate the internal characteristics and the external forcing mechanisms that contribute to erosion of coastal bluffs in the Freeport, ME 7.5' quadrangle. Data sets provided by the Maine Geological Survey include the Coastal Bluffs and Landslide Hazards (CBLH) coverage, which provides information on the relative stability of eroding bluffs; and the Coastal Maine Geologic Environments (CMGE) coverage identifies the subtidal, intertidal, and supratidal environments for the entire coast of Maine. The degree of development in the coastal zone was determined by air photo interpretation and digitized into a useable format for GIS analysis. Initial results show that: (1) mudflats and low-energy beaches in the intertidal zone are most commonly associated with unstable and highly unstable bluffs, (2) those bluffs with a high degree of exposure to incoming waves are more likely to be unstable or highly unstable. We are currently exploring the hypothesis that development on top of a bluff leads to the reduction of bluff stability by clearing vegetation cover, watering the ground, and increasing overburden pressure.