Staying Safe Flood Guide - Guadalupe-Blanco River Authority

How to Determine River Elevation
1. Locate the USGS gauge closest to your home (refer to following map and chart)
2. Calculate your potential to be flooded as follows:
a. Obtain the river stage from NWS bulletins, forecasts, etc.
b. Add that number to the datum for the gauge closest to your location to find the
present river level at MSL.
c. Compare that to the MSL for your home's slab. If there is any possibility your
home may flood, prepare to evacuate.
Example:
You live in New Braunfels and your house slab elevation is 590.0 feet mean sea level
(msl), according to your subdivision plat or floodplain permit. The closest river gauge to
you is the one located on the Guadalupe River at New Braunfels above the Comal River.
The datum for this gauge is 586.65 feet msl. Your NOAA weather radio alerts you to a
forecast peak stage of 10 feet for the gauge closest to you.
Flood potential = River Stage + Datum
= 10 Ft. + 586.65 Ft.
= 596.65 Ft.
Since your slab is at 590.0 feet, you will potentially have six feet of water in your house.
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