U.S. Floods of 1973

By C.A. Perry, B.N. Aldridge, and H.C. Ross of the USGS

Moderate to severe flooding occurred along the central coast of California in January 1973. Numerous small drainages scattered along about 300 mi of coastline had the largest discharges of record. Large flows were confined to drainages of less than 60 mi² and occurred mostly in drainage areas of less than 10 mi².

Much of the eastern half of the United States had above-average rainfall in March. Severe floods occurred March 7-9 and 15-16, with streamflow remaining high between the two flood periods in several streams in central Wisconsin. Rainfall on March 17-19 caused severe flooding from western Virginia to southwestern Mississippi. Maximum discharges at more than 100 streamflow-gaging stations in Tennessee and northern parts of Mississippi, Alabama, and Georgia were greater than the previous maximum of record. The discharge at one gauging station on the Tennessee River in Alabama was the largest since at least 1867. The storms that caused this flooding were widespread over much of the area east of the Mississippi River. Strong winds associated with the storms caused severe flooding along the shores of the Great Lakes with damage in Michigan, Ohio, and New York.

In addition to the floods discussed above, the Northeast had floods from April 24 to May 3, June 30 to July 5, and August 2. The April-May floods led to Federal disaster declarations for four counties in extreme northeastern Maine. During the May-June floods, 40 counties spread over New Hampshire, Vermont, New York, and Pennsylvania were declared eligible for Federal disaster aid. Flooding was especially severe in the Delaware River and Lake Ontario Basins. The August 2 flood was described at the time as the most deadly one in the history of central New Jersey, with six deaths recorded.

Spring floods along the Mississippi River resulted in disaster declarations for every county bordering the Mississippi River from the Wisconsin-Illinois State line to the mouth of the river in Louisiana. Floods that began on the Mississippi River and its tributaries in early March lasted through June and caused the evacuation of 50,000 people and damages of more than $400 million. New records for consecutive days above flood stage were set, and maximum stages and discharges exceeded the estimated 100-year recurrence intervals.

A significant regional flood in the Western States during 1973 resulted from the melting of excessive snowpack in the Rocky Mountains. The highwater period began in April in Arizona and extended through June in Wyoming. Extreme flooding occurred along the South Platte River in Colorado and Nebraska, both from rain on snow and from a general warm-weather snowmelt. The general snowmelt produced significant flooding in the headwaters of the Rio Grande in central Colorado and New Mexico and in the Green River and Colorado River Basins of Wyoming, Colorado, and Utah.

Several floods occurred in April, May, June, September, and November in Southern States from the Carolinas to Mississippi. Primary areas and dates of flooding were March 30-April 8 near the Georgia-Florida State line, May 27-29 in the southern Appalachian area, and June 5-6 near Atlanta, Georgia. Floods occurred near the boundary between North and South Carolina during September 13-14, and in Kentucky and Tennessee during November 25-28.

Multiple floods occurred in an arc through parts of Texas, Oklahoma, Arkansas, Kansas, and Missouri during 1973. Some streams flooded several times during the year. Widespread flooding occurred in the lower parts of the Missouri, White, Arkansas, Yazoo, and Red River Basins. Flooding occurred in basins throughout much of Texas at the time of the March-April floods along the Mississippi River. Discharges in tributaries to the Mississippi River were not historic maximums, but their combined flows caused flooding on the main stem of the Mississippi River. Widespread flooding also occurred in Texas in June and July. The July floods affected the San Antonio, Guadalupe, and Frio River Basins and a small part of the Rio Grande Basin.

Some streams reached the highest stages since the mid-1800's. Other periods of significant flooding occurred in the Texas-Missouri arc from late September through mid-October and in late November. Flood crests occurred mainly during September 26-29, October 11-13, and November 24-26, but small areas had flooding on other dates, especially September 5-7 and September 12-14. At numerous streamflow-gaging stations, discharges during late September and mid-October floods ranked highest or second highest in many years of record; at others, the November discharge was larger.

Sources: USGS.