Abstract

Bluff erosion of unconsolidated glacial sediment along the coast of Maine occurs at a relatively low rate, generally <0.5 m/yr. The chronic nature of the erosion and the continuing and rapid development along the shoreline, however, make bluff retreat a growing problem. Large landslides, such as the April 16, 1996 event, occur approximately once per decade and occasionally bring this subject to the public's mind. However, there is a general lack of understanding of bluff erosion in the region. To remedy this, the Maine Geological Survey is publishing a map series that depicts four conditions of bluff stability (highly unstable, unstable, stable, and no bluff) and intertidal shoreline type (armored, bedrock, salt marsh, and tidal flat/beach) through colors and patterns on 1:24,000 scale maps. During the course of mapping bluff stability, problems with scale and rare landslide events required an innovative method for depicting bluff stability in map form for a large region. This article presents the geological setting in which bluff erosion occurs in Maine and describes how a government agency dealt with low probablity but very hazardous events and high probability but low hazard processes in map form at a cost commensurate with the problem.

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