About FWS

The Flood Warning System

The Harris County Flood Control District’s Flood Warning System measures rainfall amounts and monitors water levels in bayous and major streams on a real-time* basis to inform you of dangerous weather conditions. The system relies on 188 gage stations strategically placed throughout Harris County bayous and their tributaries. The stations contain sensors that transmit valuable data during times of heavy rainfall and during tropical storms and hurricanes. Some gages also measure wind speed and direction, barometric pressure, air temperature, road temperature and humidity.

The purpose of the Flood Warning System website is to provide information collected by the gages in a user-friendly format directly to you. This information is used by the Flood Control District and by Harris County’s Office of Homeland Security and Emergency Management to inform you of imminent and current flooding conditions along bayous. It also is used by the National Weather Service to assist in the issuing of flood watches and warnings. Accurate rainfall and bayou/stream level data help you and emergency management officials make critical decisions that ultimately can reduce the risk of property damage, injuries and loss of life. The Flood Control District urges you and your family to use this information and take the appropriate precautions during times of heavy rain and flooding. You are encouraged to monitor bayou/stream levels near your homes, places of work and areas along your daily commutes.

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

History of the Flood Warning System

The 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, and the system provided invaluable information, including rainfall totals and bayou/stream level data that was not previously available. From 1983 to 2021, the number of gage stations increased to today’s total of 188, expanding the ability to monitor and gather information from many more bayous and streams.

How the Information is Used

The primary function of the Flood Warning System is to transmit rainfall and bayou/stream level data for use by you and by government officials in taking steps to protect the public. The information received is collected and analyzed by the Flood Control District also to develop post-flood reports. These reports detail the extent and impact of flooding, including an approximation of the number of structures inundated from a flood. In addition, the Flood Control District uses this information to perform engineering analyses for identifying locations of future projects as well as to determine the effectiveness of constructed projects.

How the System Works

When it begins to rain, data-collecting sensors at each gage station transmit rainfall amounts via radio frequency every time 0.04 inches of rain is measured by the sensor. Sensors that transmit bayou/stream levels report every 0.10 foot rise in water levels.

The sensors transmit information to four primary repeaters located in the Huffman, Clodine, League City, and Tomball areas. The repeaters then relay the data to primary and back-up base stations located at Houston Transtar and at the Harris County Household and Hazardous Waste Facility. The information is monitored daily by software and by Flood Control District staff to ensure the gages are properly functioning and transmitting accurate data.

In addition to the data collected at the gage stations, data also is transmitted to the Flood Control District from gages that are monitored and maintained by partner agencies: 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. Both the Flood Control District and our partners’ data are available to you through the mapping tool on this website.

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.