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

Arkansas is located in the south-central United States. The weather in Arkansas is affected by the prevailing westerlies, which are part of the atmosphere's general circulation pattern. The weather systems typically move from west to east. The primary source of moisture is the Gulf of Mexico, and the Pacific Ocean is a secondary source. Mean annual precipitation in Arkansas ranges from about 40 in. in the Arkansas Valley north of the Ouachita Mountains to 56 in. in the Ouachita Mountains (Paulson and others, 1991).

Flooding characteristics in Arkansas depend on the season. In the winter, flooding is generally widespread and lasts for several days. Flooding in the summer is typically local and short-lived.

On the basis of regionalization procedures that relate flood characteristics to watershed and climatic characteristics, the magnitude of maximum discharges for streams in Arkansas is dependent on drainage area of the basin, channel slope, and channel length. In the upland area of the State, mean basin elevation and mean annual precipitation replace channel length as factors affecting maximum discharge (Jennings and others, 1994).

The most extensive flood in Arkansas during 1970-89 was the flood of December 1982. Thirty-two percent of the State's streamflow-gaging stations recorded significant discharges. The flood mostly affected northern and western Arkansas. On December 3, 1982, rainfall amounts exceeded 12 in. in 24 hours (Paulson and others, 1991). Maximum discharges matching or exceeding the 100-year recurrence interval were recorded at 21 gaging stations, and maximum discharges with at least a 25-year recurrence interval occurred at 27 additional gaging stations. Several tornados caused damage along the eastern edge of the flooded areas.

During 1973 and 1974, Arkansas had unusually large amounts of precipitation. A flood during June 1974 resulted in discharges with 100-year recurrence intervals at six streamflow-gaging stations. Thirteen percent of the gaged streams recorded significant discharges during these years.

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.