In 1998, the Blanco River had peak flooding discharge of from a basin. Early in the morning on May 24, during the 2015 Texas–Oklahoma floods, the Blanco River experienced catastrophic flooding. The river at Wimberley rose more than 30 feet in less than three hours, and set a new record high crest of more than 40 feet while disabling the gauge. Rainfall totals of 10 to 13 inches were reported upstream in southern Blanco County, and all of this water entered the Blanco River and Little Blanco River. The Fischer Store Rd. bridge over the Blanco River was destroyed by flood waters west of Wimberley. The Blanco River, down stream from the bridge, at Wimberley reached a record crest. The gauge failed at 40 feet and the USGS later estimated the crest at 44.9 feet with peak flow of. This height was more than 10 feet over the previous record height of 33.3 feet from 1929. Homes along the banks of the Blanco River from the City of Blanco, through Wimberley, and down to San Marcos experienced an historic flood. Many homes were totally destroyed and swept down stream. Many homes were struck by large debris, including full size cypress trees which typically lined the banks of the river. A house in the 100 block of Deer Crossing Ln. in Wimberley was washed away in the flood with nine people inside. There was one lone survivor while eight others died. Six bodies were recovered and the two small children remain missing. Several of the bodies were recovered near San Marcos, Texas nearly 30 miles downstream. Ten fatalities were reported for this event. The river experienced rises that exceeded 20 feet in one hour. Estimates of insured losses are around $100 million. Overall in Hays County, including Wimberley and San Marcos, 321 homes were destroyed, with hundreds more heavily damaged. During the May 24 event, the river crested at 36.52 ft at Kyle, Texas, which was the highest the river had been since a 40.0 ft crest in 1929. Kyle is downstream of the Wimberley gauge. On October 30, 2015, the river flooded again. The river crested at 37.24 ft at Kyle, exceeding the gauge height of the May 24, 2015 crest, becoming the highest the river had been since a 40.0 ft crest in 1929. The Wimberley gauge had a crest of only 26.54 ft on October 30, 2015. Flooding near San Marcos culminated in the closure of the Interstate 35 bridge over the Blanco River for the second time in 2015.
Geography
The upper reaches of the Blanco River are hilly, and the river's slopes are frequently steep. As the river reaches the Balcones Escarpment near San Marcos, it widens and its slopes moderate; this is typical of rivers in the central part of the state.
