Flooding and Heavy Rain

Flooding is the most frequent and damaging natural hazard in Greater Houston. The combination of flat coastal-plain topography, clay soils that absorb water slowly, dense development, and intense subtropical rainfall produces flood events on a scale most of the country does not experience. Tropical Storm Allison dropped more than 35 inches of rain on parts of the city in 2001. Hurricane Harvey produced more than 50 inches in some areas in 2017. Localized flash flooding from ordinary thunderstorms occurs several times each year.

Understanding the Bayou System

Houston drains through a network of bayous managed in part by the Harris County Flood Control District. The four bayous that most often appear in flood reporting are Buffalo Bayou, which runs west to east through the center of the city; Brays Bayou, which drains much of southwest Houston and the Texas Medical Center area; White Oak Bayou, which serves the near northwest; and Sims Bayou, which serves the south side. Addicks and Barker reservoirs west of the city are designed to hold water during major events and release it slowly downstream into Buffalo Bayou.

High-Water Locations

Certain Houston intersections and underpasses flood predictably. The underpasses along I-610, I-69 (formerly US-59), and I-45 inside the Loop close routinely during heavy rain. The intersection at Memorial and Shepherd, the I-10 feeder near Heights Boulevard, and several low-water crossings in Meyerland and Bellaire have long histories of flooding. The TranStar website (houstontranstar.org) maintains a real-time map of high-water locations and roadway closures.

Vehicle Flood Safety

The single most repeated piece of guidance from the National Weather Service is turn around, don't drown. Two feet of moving water can carry away most vehicles, including pickups and SUVs. Floodwater depth is almost impossible to judge at night or when the road surface is obscured. If you encounter standing water across a roadway, turn around and find an alternate route. See our severe weather road conditions page for additional driving guidance.

Home Preparation

Households in flood-prone areas should consider sandbags or flood barriers at door thresholds, elevating valuables and electronics, and moving vehicles to higher ground before a forecast event. Know whether your home is in the 100-year or 500-year floodplain — Harris County maintains updated maps, and many neighborhoods were re-mapped after Harvey. Document the contents of your home with photographs or video and store the files off-site.

Flood Insurance Basics

Standard homeowner's and renter's insurance policies do not cover flood damage. Flood coverage is generally purchased through the National Flood Insurance Program or, increasingly, through private carriers. NFIP policies typically have a 30-day waiting period before coverage takes effect, so the time to purchase is well before a storm enters the Gulf. Renters can purchase contents-only flood policies, which are often affordable and overlooked.