SUMMARY OF SIGNIFICANT FLOODS IN THE UNITED STATES, PUERTO RICO, AND THE VIRGIN ISLANDS, 1970 THROUGH 1989 Prepared by the U.S. Geological Survey Water-Supply Paper 2502 ABSTRACT Mississippi is located in the southeastern United States and is bordered on the south by the Gulf of Mexico and on the west by the Mississippi River. Mississippi has a humid climate. The principal source of moisture is the Gulf of Mexico. During most of the year, tropical airmasses bring moisture inland from the Gulf. Occasionally, Pacific moisture reaches Mississippi, but this is rare. The summer months usually bring airmass-type thunderstorm activity with local intense rainfall. The threat of hurricanes and tropical storms exists from mid-summer to late fall. Rainfall in the late fall to late spring is usually caused by frontal systems that can stall out and persist for several days. Mean annual precipitation ranges from about 50 inches in the north to about 68 inches near the coast of the Gulf of Mexico in southeastern Missisippi. Flooding in Mississippi usually is associated with excessive rainfall from stalled frontal systems during the winter and spring months. Flooding from severe thunderstorms associated with cold fronts or squall lines can occur in any month. Tropical storm and hurricane flooding can be caused by excessive rainfall and from storm surges along the Coast. On the basis of regionalization procedures that relate flood characteristics to watershed and climatic characteristics, the magnitude of maximum discharges for streams in Mississippi is dependent upon the drainage area, main-channel slope, and the main-channel length, from the point of discharge to the drainage divide. Significant flooding occurred in April and May 1983 when a series of storms produced excessive rainfall statewide. In April, 15 streamflow-gaging stations recorded maximum discharges with recurrence intervals equal to or greater than the 100-year recurrence interval. Forty percent of the streamflow-gaging stations in the southern part of the State recorded maximum discharges with recurrence intervals greater than the 20-year recurrence interval. The flooding in May was caused by excessive rainfall of the northern two-thirds of the State. This flooding caused one death and damages of approximately $500 million. The Easter flood of April 1979 on the Pearl River was the largest and most damaging flood in recent history. The flood was a result of a major storm that produced rainfall totals of 12 to 21 inches in the headwaters of the Pearl River. The discharges recorded on the main stem of the Pearl River were generally equal to or greater than the 100-year recurrence interval. Twenty percent of the streamflow-gaging stations in the State recorded significant discharges at this time. During the flood of 1973 that occurred from March through May, 15 percent of the gaging stations in the State recorded significant discharges. The March flood resulted in maximum discharges greater than the 100-year recurrence interval at some stations in the Tombigbee River Basin, and in the Yazoo River Basin, floodwater passed over the emergency spillways of four flood-control dams. These floods were part of a major regional flood that extended from Mississippi and Tennessee to Alabama and Georgia. As a result of the 1973 floods, 19 lives were lost, and more than $200 million in damages were sustained in Mississippi. The location of streamfow-gaging stations in Mississippi that had significant floods for 1970-89 is shown in figure 46 by station number. The specific data for each signficant flood are listed in table 25. A signficant flood is one that ranks in the top 5 percent of all annual maximum discharges for that station's period of record. LizardTech's Djvu plug-in is needed to view these reports. CLICK HERE TO VIEW THE ENTIRE REPORT For questions or comments, contact K. Van Wilson.