U.S. Floods of 1976

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

An unusually intense winter storm hit the island of Oahu, Hawaii, on February 7, 1976. As much as 4 in. of rain fell in some areas during a period of 1.5 hours. Between 17 and 20 in. total fell throughout the course of the storm. Streams draining the western slopes of Oahu's mountains reached record high discharges.

Snowmelt during March and April caused prolonged flooding in North Dakota and Minnesota. Warm temperatures during the last week of March began melting an 18-in. snowpack. Flooding was the worst in the Souris River Basin of North Dakota. As record stages were being recorded at streamflow-gaging stations, a 6-week advance forecast of the severity of the floods gave time to improve levee systems in North Dakota preventing much additional damage.

On May 30, a weak cold front stalled over Tulsa, Oklahoma, for several hours. Total rainfall of 7 to 10 in. was unofficially reported. Previous maximum gage heights were exceeded by 1 to 3 ft at two streamflow-gaging stations on Mingo Creek. Flooding covered a larger area and caused more damage than any previously known flood along Mingo Creek.

The greatest flood disaster of 1976 occurred on June 5 when the Teton Dam in Idaho failed. The Teton Dam is located on the Teton River in the headwaters of the Snake River Basin. The dam was breached as the reservoir was filling for the first time. About 173,000 acre-ft of water drained through the dam in 2 hours and 23 minutes. The maximum discharge downstream from the dam was estimated at 2.3 million ft³/s. The flood caused 11 deaths, and damages were estimated at $400 million.

Severe floods hit the Houston, Texas, metropolitan area on June 15. The floods were caused by intense rainfall totalling as much as 13 in, most of which fell within a 3-hour period. The discharge of the Brays Bayou was 29,000 ft³/s, which is considered the 40-year recurrence interval. Eight deaths and an estimated $25 million in damages resulted from the flood.

A storm producing 4 to 6 in. of rain on June 19-20 hit south-central New York and north-central Pennsylvania. The rain produced unusually large maximum discharges in small tributaries to the Chemung River near Corning and in the headwaters of Catharine Creek.

On July 3 and 4, large floods occurred in southeastern Kansas. Otter Creek and Elk River were the most affected by the 4 to 8 in. of rain that fell during 2 days. The maximum stages on Otter Creek and Elk River were the largest known for their periods of record. The Walnut River at El Dorado was reported to have crested almost 1 ft above the previous maximum stage.

The second largest flood disaster of 1976 was the Big Thompson River flood in Colorado. The area most affected by the flood was the Big Thompson Canyon, especially the area downstream from Estes Park, Colorado. The flood was caused by a storm on July 31 through August 1, with rainfall amounts totalling as much as 12 in. in some areas (National Oceanic and Atmospheric Administration, 1976); an estimated 7.5 in. of rain fell in some areas in 1 hour. Maximum discharges on the North Fork Big Thompson and Big Thompson Rivers exceeded previously recorded maximums at several locations. Reports of an estimated 19-ft high wall of water rushed through Big Thompson Canyon destroying everything in its path. In the narrows of the canyon, stream levels rose to 14 ft above pre-flood levels and washed away 1.9 mi of highway. The flood resulted in 139 deaths and 6 missing persons, destroyed 323 homes and 96 mobile homes, and damaged many other homes. Two counties were declared Federal disaster areas, and the flood caused $41 million in damages.

Sources: USGS.