Local context
Water and flooding around San Marcos: the local picture
San Marcos lies on the Interstate 35 corridor between Austin and San Antonio, where the Hill Country meets the coastal plain. The San Marcos River flows through the city and the Blanco River joins it nearby, so two river systems shape flood risk here instead of one. Homes near either river, and near the creeks that feed them, sit closest to storm water, while low crossings across town can close during a flash flood even when the rivers themselves stay in their banks.
That river geography is why San Marcos homeowners need a flood plan before storm season, not during it. Check the official flood zone for your address, know which roads flood first, and keep valuables off ground floors near the rivers. When water does enter a home, the clock matters: river and ground water is treated as contaminated, porous materials it soaks are removed rather than cleaned, and drying starts only after the space is sanitized. Plumbing losses away from the rivers follow the same fast sequence, with extraction first and meter readings every day until the structure tests dry.
- Area: San Marcos, Hays County, with parts in Caldwell and Guadalupe counties, in Central Texas
- Waterway: The San Marcos River and Blanco River meet near the city, and the Blanco River flooded severely on Memorial Day weekend in 2015.
- Coverage: 1 local ZIP code, 78666
- Response: 24/7 local crews, 60-minute target for active water in San Marcos