Floodplain Information

Public Invited to Appeal or Comment on Flood Maps for Caldwell, Gonzales, Guadalupe, & Hays Counties

New preliminary flood risk information and updated Flood Insurance Rate Maps (FIRM) will be available for review by San Marcos residents and business owners beginning January 25. Individuals may view preliminary maps online or visit the Engineering and Capital Improvements office on the second floor of the Municipal Building, 630 E Hopkins Street.

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.

Useful Documents