SUMMARY OF FLOODS IN THE UNITED STATES DURING 1990 AND 1991
Floods of April and May, 1991 in Mississippiby W. Trent Baldwin
Prepared by the U.S. Geological Survey as Water-Supply Paper 2474
1996
ABSTRACT
April and May 1991 were two of the wettest months on record in Mississippi. For the most part, the record rainfall was not a result of one very intense storm system, but rather a persistent pattern of storms. Rainfall totals for the 2 months in the State ranged from 16 to 38 inches. The April 1991 rainfall totals ranged from 6.5 to 22.8 inches, whereas the normal rainfall in April ranges from 5.2 to 6.4 inches. At 18 precipitation data sites, April 1991 was the wettest month on record; at 56 sites, it was the wettest April on record. Although the northeastern part of the State received from 8 to 12 inches of rain from May 25 to May 27, it was the persistent pattern of storms that resulted in the excessive rainfall. The rainfall totals in this region for May 1991 ranged from 5.9 to 23.4 inches, whereas normal rainfall ranges from 3.8 to 5.8 inches. At four precipitation data sites, May 1991 was the wettest month on record, as 22 sites, it was the wettest May on record.
As a result of the record-breaking rainfall during April and May, flooding occurred in every major drainage basin in the State. Maximum stream stages and discharges for 109 flood- determination sites (fig. 63) are summarized in table 53. Maximum discharges equaled or exceeded the discharge for the 100-year recurrence interval at 7 sites, the 50-year recur- rence interval at 13 sites, and the 10-year recurrence interval at 35 sites.
Flooding was more severe in the Yazoo River Basin in northwestern Mississippi and the Mobile River Basin in northeastern Mississippi than in other drainage basins in the State. The U.S. Army Corps of Engineers operates flood-retarding structures on the Little Tallahatchie, Yocona, Coldwater, and Yalobusha Rivers in the Yazoo River Basin. These structures experienced the largest floods since at least 1973 and had emergency- spillway flows for more than 70 consecutive days. In the Mobile River Basin, floods on the Tombigbee River were also the largest since at least 1973.
The U.S. Army Corps of Engineers supplied more than 1 million sandbags and 30 pumps for flood control in northwestern Mississippi. Inmates from the State Penitentiary and guardsmen from the Mississippi National Guard participated in the sandbagging effort. At least one death was attributed to the floods--a 9-year old boy drowned while swimming in the swift current of a creek. The State Highway 6 bridge over the Tombigbee River was closed when one of the piers settled about 1 foot. More than 2 million acres of land were inundated by floodwater, and 1,700 homes were damaged. Damage caused by these floods was estimated in the hundreds of millions of dollars.
FIGURES
63. Location of flood-determination sites for floods of April and May 1991 in Mississippi.
TABLES
53. Maximum stages and discharges prior to and during floods of April and May 1991 in Mississippi.
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