Summary of Significant Floods in the United States, Puerto Rico, and the Virgin Islands, 1970 Through 1989

Maine is located in the extreme northeastern part of the United States with Canada to the north and east and the Atlantic Ocean to the south. Three airmasses dominate Maine's climate. These are the polar continental, which are cold, dry airmasses originating in Canada and Arctic areas; tropical maritime, which are warm, moist airmasses originating in the Gulf of Mexico and adjacent subtropical water of the Atlantic Ocean; and polar maritime, which are cool, damp airmasses from the North Atlantic. Land-recycled moisture is also an important source of moisture because it supplements the major sources of moisture with evaporation from lakes and reservoirs and from the land surface.

Maine receives abundant precipitation annually. There is a generally uniform distribution of precipitation throughout the entire year. Mean annual precipitation in the northeast is 34 in. and 55 in. in the southeast. The statewide mean annual precipitation is about 42 in. (Paulson and others, 1991).

Maine receives widespread flooding when frontal systems stall over the eastern seaboard causing intense rainfall. Flooding also occurs from rapid snowmelt, ice jams, and hurricanes. Smaller scale flooding in Maine results from convective thunderstorms in the summer months.

On the basis of regionalization procedures that relate flood characteristics to watershed and climatic characteristics, the magnitude of maximum discharges for streams in Maine is dependent on drainage area of the basin, channel slope, and storage, which is the area of lakes and ponds in the basin as a percentage of total area (Jennings and others, 1994).

The flood of April 1987 was the most destructive in Maine's history. The flood was caused by a slow-moving frontal system. The intense rains associated with the frontal system combined with the melting snowpack and resulted in flooding conditions. Thirteen streamflow-gaging stations recorded record maximum discharges. During the April 1987 flood, 61 percent of the gaging stations in the State recorded significant discharges. Fourteen of Maine's 16 counties were declared disaster areas, and damage estimates exceeded $100 million (Paulson and others, 1991).

Jennings, M.E., Thomas, W.O., Jr., and Riggs, H.C., 1994, Nationwide summary of U.S. Geological Survey regional regression equations for estimating magnitude and frequency of floods for ungaged sites: U.S. Geological Survey Water-Resources Investigations Report 94-4002, 196 p.

Paulson, R.W., Chase, E.B., Roberts, R.S., and Moody, D.W., compilers, 1991, National water summary, 1988-89-Hydrologic events and floods and droughts: U.S. Geological Survey Water-Supply Paper 2375, 591 p.