Water School

A 50-year flood is a high streamflow that overflows the natural or artificial banks of a waterway and has a two percent chance of occurring in any given year.

A 10-year flood is a high streamflow that overflows the natural or artificial banks of a waterway and has a 10% chance of occurring in any given year.

As the name implies, water supply lakes are built primarily to provide a place to store water for Texas residents, communities, businesses, agriculture, industry and others who all depend on water to survive and thrive. Such lakes are especially vital during periods of drought, when other sources of water may be limited.  Many of Texas’ flood control lakes serve a secondary purpose as a water storage facility.  However, reservoirs designed for water supply, do not necessarily also provide flood...

The great majority of our lakes (reservoirs) in Texas were built to help tame the state’s rivers and streams, which from time to time would swell beyond their banks and cause devastating floods. Such was the case with the Brazos River. History books record numerous destructive floods took place in the Brazos basin before a series of dams were built along its length to create reservoirs to hold periodic flood waters.

A flood pool is a specified area within a flood control lake and the surrounding land that may only be inundated during periods of flooding. This allows the flow of waters to be regulated and released in a safe manner.

A 100-year flood is a flood event that it has a 1 percent chance of happening in any given year. The term “100-year” is a measure of a flood’s size, not how often it occurs. Although statistically unlikely, several 100-year floods can occur within the same year or a few short years. It is also called the base flood.