U.S. Floods of 1978

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

The first significant flood of 1978 resulted from the February 6 and 7 "Blizzard of 1978." This storm formed in the Carolinas and moved northward along the Atlantic seaboard. The storm produced record amounts of snow and hurricane-force winds. Record tidal flooding occurred from Boston, Massachusetts, northward to Portland, Maine. Total economic losses from the storm, including damages directly caused by the storm and costs of snow removal, approached $1 billion.

Spring floods accompanied melting of a large snowpack in the Red River of the North Basin and the Missouri River Basin in the North-Central States. Flooding in different areas continued through the spring months. Above-average precipitation had produced a large, wet snowpack over much of Minnesota, North Dakota, South Dakota, eastern Montana, and parts of northern Nebraska and western Iowa. Much of the ground in the Missouri River Basin froze earlier than normal during the winter season when the ground had a high-moisture content, and the frozen ground would not absorb the snowmelt. Consistently warm temperatures and rains on March 11-12 caused rapid snowmelt throughout the basin and flooding conditions within a few days. A maximum discharge of record was recorded on the Wild Rice River at Hendrum, Minnesota.

Flooding occurred in Wyoming and southern Montana as the result of intense rains that began the evening of May 16 and continued through the morning of May 19. Before the rain, the streams in the area were already flowing at or near bankfull because of snowmelt and above-average precipitation earlier in the spring. Fourteen streamflow-gaging stations in Montana recorded discharges at or above the 100-year recurrence interval, and about one-fifth of the 164 stations in Montana recorded maximums of record due to this flood.

June and July were very wet months for Minnesota and Wisconsin. Storms caused flash flooding on many different occasions throughout the 2 months in both States. Flooding on July 1-3 was particularly severe in the Kickapoo River Basin of southwestern Wisconsin. The flood caused discharges that are the maximums of record at 11 gaging stations with recurrence intervals of 100 years or greater. On July 5 and 6, Rochester, Minnesota, received intense rains. The National Weather Service rain gage at the airport recorded 4.99 in. of rain over a 3-hour period. The total rainfall far exceeded the amount of a 100-year recurrence interval for that time period. The floods caused by the storm were the largest of record since 1888 on Bear and Silver Creeks and the largest of record on the South Fork Zumbro River since 1855. At the headwaters of the Cedar River, a record-setting flash flood occurred on July 16 and 17, which was the second flash flood in 11 days.

On June 18, the U.S. Geological Survey made a measurement of an extremely high discharge of 3,250 ft³/s for a 1.71-mi² drainage area in the headwaters of a small tributary for Honey Creek in central Ohio. The 100-year recurrence-interval discharge for this site is slightly more than 1,000 ft³/s. Rainfall of 7 to 8 in. in 2 hours caused this significantly large flood. This amount of rain is well above the 3 in. calculated for the 2-hour, 100-year rainfall in the area.

Tropical Storm Amelia brought extremely intense rains to central Texas on August 1-4. Rainfall of more than 48 in. in 72 hours occurred northwest of the town of Medina. More than 30 of the 48 in. occurred on August 2, setting a point rainfall record for the United States. In response to the large rainfall, significant flooding occurred in the Medina River Basin. The upstream reaches of the Guadalupe and Medina Rivers had the highest floods recorded since records began for each station in 1848 and 1880, respectively. Thirty-three deaths occurred, and the damage totals for the area were estimated at $110 million.

Significant floods occurred from Michigan to Texas between September 11 and 14. Many areas had flash flooding as a result of storms moving through the area. Some areas received as much as 10 in. of rainfall. The hardest hit areas were central Arkansas and northern Louisiana, and Federal disaster declarations were made for two counties in each area. Little Rock, Arkansas, received 10 to 13 in. of rain the morning of September 13. At several stations the 6-hour rainfall total was well above the 100-year recurrence interval.

Two storms, the first from December 3 to 5 and the second from December 7 to 10, caused record flooding in Kentucky and West Virginia. Flooding was most severe in the Licking, Kentucky, Salt, and Green River Basins, and along the Ohio River. Maximum discharges of record were recorded at many stations in the Tygarts Creek, Kentucky River, and Salt River Basins. In West Virginia, discharges with recurrence intervals greater than 100 years were recorded in the Twelvepole Creek Basin. Total damages for the flood were estimated to be greater than $100 million in Kentucky and $12 million in West Virginia.

The Southwest experienced recurrent flooding from November through the end of the year as a result of a persistent series of upper-level low-pressure systems that developed off the southwest coast of California. These low-pressure systems caused frequent periods of widespread and above-average precipitation in Arizona and New Mexico. Floods with recurrence intervals greater than 50 years occurred in the Gila River Basin.

Sources: USGS.