Floodplain Information

Flooding in San Marcos

Flooding in our city is primarily caused by three sources: the San Marcos River, the Blanco River, and Purgatory Creek. Floodwaters can cover many blocks up to three or four feet deep.


Flooding in all three areas can come with little warning. A flood in October of 1998 covered streets within 30 minutes of forming. In November of 2001 the Blanco River flooded within an hour after a thunderstorm started. Floods are also dangerous. Even though they appear to move slowly (three feet per second), a flood two feet deep can knock a man off his feet and float a car.

Property Elevation

Your property may be high enough that it was not flooded recently. However, it can still be flooded in the future because the next flood could be worse. If you are in the floodplain, the odds are that someday your property will be damaged.