The river is generally quite shallow, and it briefly dips below ground in some areas in the Hill Country.

In 1998, the Blanco River had peak flooding discharge of 2,970 cubic metres per second (105,000 cu ft/s) from a 1,067 square kilometres (412 sq mi) basin.

The Fischer Store Road bridge over the Blanco River west of Wimberley was destroyed by flood waters.

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 Lane in Wimberley was washed away in the flood with nine people inside; one person survived while eight others died.

Overall in Hays County, including Wimberley and San Marcos, 321 homes were destroyed, with hundreds more heavily damaged.

Flooding near San Marcos led to closure of the Interstate 35 bridge over the Blanco River for the second time in 2015.