Flash Flood in Custer County, South Dakota

Heavy rain estimated at four to six inches fell west of Hermosa between 6 pm and 8 pm MST. Battle and Grace Coolidge Creeks overflowed their banks and several dry canyons filled with water and drained into the creeks. State highways 40 and 36 were flooded in numerous spots. A river gauge on Battle Creek just east of Hermosa crested at 14.91 feet at 9 pm, rising from 2.63 ft at 7:30 pm and above the flood stage of 8.0 feet. About six inches of water covered Highway 79 at the Battle Creek bridge. A railroad bridge about 3/4 mile downstream became clogged with debris and water rose behind the embankment and flooded six homes. At about 8:30 pm MST, a section of the embankment failed, flooding a new subdivision on the other side. All of the approximately 20 houses were damaged; three homes were washed off their foundations, and one of those houses was carried a half a mile east of the subdivision by the flowing water. There were no injuries.

Severe thunderstorms developed between Custer and Hermosa; producing large hail, gusty winds, very heavy rain, and flash flooding.