Low-Cost Bluff-Stability Mapping in Coastal Maine: Providing Geological Hazard Information Without Alarming the Public

¹ Maine Geological Survey, 22 State House Station, Augusta, ME 04333
² University of Maine, Department of Geological Sciences, Orono, ME 04469-5790

Joseph T. Kelley was born and raised in Portland, Maine. He obtained a B.A. in Geology from Boston University in 1973 and a Masters and Ph.D. from Lehigh University in 1976 and 1980, respectively. He taught coastal geology courses at the University of New Orleans from 1979–1982, when he returned to Maine and became the State's Marine Geologist with the Maine Geological Survey. From 1982–1999, Dr. Kelley was based at the University of Maine where he conducted research. He has written numerous technical papers and books and was the associate editor for geological processes for the Journal of Coastal Research for 5 years. In July, 1999 Dr. Kelley took a joint position at the University of Maine in the Department of Geological Sciences and School of Marine Sciences. He is a member of the Geological Society of America, Society for Sedimentary Geology, American Association for the Advancement of Science, and the Coastal Education and Research Foundation.

Stephen M. Dickson is a Marine Geologist with the Maine Geological Survey in Augusta. He has been there since 1986 and has conducted numerous studies of beaches, coastal geology, physical oceanography, and coastal hazards. Current research includes combined-flow sediment transport by storms, coastal bluff erosion, and wake impacts of high-speed ferries. Dr. Dickson received a B.A. from Wesleyan University, an M.S. from the Graduate School of Oceanography at the University of Rhode Island, and a Ph.D. in Oceanography from the University of Maine. He is a member of American Geophysical Union, Geological Society of America, and Society of Economic Paleontologists and Mineralogists.

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.