About FWS

The Flood Warning System

The Harris County Flood Control District’s Flood Warning System measures rainfall and monitors stream elevations on a real-time* basis to inform the public of changing and potentially dangerous weather conditions. The system relies on 201 gage stations strategically placed throughout Harris County streams and their tributaries. In addition, the Flood Warning System website provides data for more than 350 gage stations across the region, including those owned by partner agencies.

Each gage station contains sensors that transmit critical data during heavy rainfall and tropical weather events. Some gages also measure wind speed and direction, barometric pressure, air temperature, and relative humidity.

This website also provides information on historical rainfall and flooding events, Harris County watersheds and frequently asked questions.

History of the Flood Warning System

Installation of the gage system began in 1982 under the direction of the Flood Control District and initially included 13 gage stations. The first test of this system occurred during Hurricane Alicia in 1983, providing valuable information, including rainfall totals and stream elevation data that was not previously available.

Since 1983, the number of gage stations steadily increased, expanding the ability to monitor and gather information from many more streams in the region. 

How the Information is Used

This information is used by residents, media, the National Weather Service, emergency management agencies, and the Harris County Flood Control District to monitor current conditions and assess flood risk across the region. Accurate rainfall and stream elevation data help residents and emergency management officials make critical decisions that can ultimately reduce the risk of property damage, injuries, and loss of life. The Flood Control District urges everyone to use this information and take the appropriate precautions during times of heavy rain and flooding. 

The Flood Control District also uses this information to develop post-flood reports, estimate the extent and depth of flooding along streams, and estimate the number of structures impacted. 

How the System Works

When rainfall occurs, sensors at each gage station transmit rainfall data via radio frequency every time 0.04 inches of rain is recorded. Stream elevation sensors report changes for every 0.10 foot rise. 

The information is transmitted through a network of repeaters located in the Huffman, Clodine, League City, Tomball, Needville areas, then relayed to primary and backup base stations at Houston Transtar and the Harris County Household and Hazardous Waste Facility. 

Flood Control District staff and automated systems continuously monitor incoming data to ensure accuracy and reliability. 

In addition to Flood Control District gages, the system incorporates data from partner agencies including: Brazoria Drainage District No. 4, City of Friendswood, City of League City, City of Missouri City, City of Mont Belvieu, City of Sugar Land, Fort Bend County, Galveston County Drainage District No. 1, Waller County, The Woodlands, and the Trinity River and San Jacinto River Authorities. Together, this combined network provides broader regional coverage and a more complete picture of rainfall and flooding condtitions.

The Flood Warning System is similar to other warning systems across Texas and throughout the United States. Similar networks are found in Maricopa County, Arizona; Los Angeles, California; Denver, Colorado; Overland, Kansas; and Las Vegas, Nevada. In Texas, the city of Dallas, the Jefferson County Drainage District and the Lower Colorado River Authority operate similar complex networks.

* The data presented on this mapping tool and website may be delayed by approximately five minutes.