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

Connecticut is located on the East Coast and is bordered on the south by Long Island Sound, an inlet of the Atlantic Ocean. Connecticut's climate is temperate humid. The primary sources of moisture are the Atlantic Ocean and the Gulf of Mexico. The proximity of the Atlantic Ocean to Connecticut has a distinct effect on the State's climate. The four primary weather systems that generally affect Connecticut are: (1) coastal storms of extratropical origin called "northeasters"; (2) low-pressure systems that move northeastward along the Appalachian Mountains; (3) tropical cyclones, including hurricanes; and (4) local thunderstorms. The precipitation in the State is generally plentiful and distributed evenly over the entire State, averaging about 46 in.

On the basis of regionalization procedures that relate flood characteristics to watershed and climatic characteristics, the magnitude of maximum discharges for streams in Connecticut is dependent on drainage area of the basin, 24-hour precipitation, channel length, channel slope, and percentage of drainage area underlain by coarse-grained stratified drift (Jennings and others, 1994).

The flood of June 1982 was the most extensive in Connecticut during 1970-89. Thirty percent of the streamflow-gaging stations recorded significant discharges. The flood was caused by a low-pressure system that formed over the Gulf States and moved northward. The storm affected primarily south-central and southeastern Connecticut. Approximately 25 percent of the State was affected by floods equal to or exceeding the 100-year recurrence interval. Flash flooding occurred on numerous small streams throughout most of Connecticut. The effects of the June 4-7 storm were compounded in many locations by 4 in. of rain that saturated the soils and filled reservoirs to near capacity the previous week. Throughout the State, precipitation totals were high. The central and south-central parts of the State received from 8 to 16 in. of rain in approximately 48 hours. In Connecticut, the 24-hour precipitation for a recurrence interval of 100 years is between 7 and 8 in. The 48-hour precipitation for a recurrence interval of 100 years is between 9 and 10 in. (Hershfield, 1961).

Hershfield, D.M., 1961, Rainfall frequency atlas of the United States: U.S. Department of Commerce, Weather Bureau Technical Paper 40, 115 p.

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.