Floods of September-October 1967 in south Texas and northeastern Mexico

Abstract

Floods produced by Hurricane Beulah during September and October 1967 were outstanding because of the magnitude of the stage and discharge and because of the number of river basins affected. Previously known maximum stages were exceeded, at the downstream station, in five river basins in Texas by amounts ranging from 2.7 feet at Guadalupe River near Tivoli to 9.2 feet at Aransas River near Skidmore. The greatest relative maximum discharge recorded during the storm occurred at Medio Creek near Beeville, where the peak discharge was 4.1 times the previous maximum since 1919 and 6.0 times the magnitude of a regional 50-year flood. The inflow to Lake Corpus Christi was more than 4.5 times the volume of the lake at spillway elevation. Because of the large volume of fresh-water inflow to bays and estuaries along the Texas coast, the salinity of the water was greatly reduced. Data collected in Nueces Corpus Christi and Guadalupe San Antonio Bays show that dilution proceeded rapidly along the line of flow. Fresh-water inflow to Corpus Christi Bay exceeded 60,000 cubic feet per second from September 23 through September 28. The total inflow was about 1.5 times the volume of water normally in the bay, but because of its shape and depth, the bay was not entirely flushed of saline water. Fresh-water inflow to San Antonio Bay exceeded 40,000 cubic feet per second from September 21 through September 26. The total inflow was more than three times the volume of water normally in the bay, and most of the saline water was flushed from the bay. Measurements of water levels in wells indicate that Hurricane Beulah caused significant rises in water levels in shallow wells by percolation of rainfall and ponded waters and by the cascading of floodwaters directly into numerous inundated wells. Flooding along the Rio Grande and its floodways below Falcon Dam was the greatest since the American floodway system was completed in 1926. At Mission Branch Floodway, south of McAllen, Tex., the peak discharge was 2.15 times the previous maximum in 1932. The peak stage exceeded the previous maximum by 4.14 feet. Flooding along the Mexican floodways destroyed all stream-gaging equipment. A 4,000-square-mile area of south Texas having no defined drainage system contains thousands of shallow wind-formed depressions. These normally dry depressions were inundated by the storm runoff, which produced a vast amount of ponded water. The ponds blocked highways for several days and hampered ranching and oil field operations for months after the storm. Rainfall measurements of 25 inches during the period September 19-25, 1967, were common in Texas, and as much as 35 inches was measured in Mexico. Total damage in 39 counties of Texas was estimated by the Galveston District of the Corps of Engineers to be $168,844,000.