Floods

Texas is no stranger to flooding, but climate change is making these natural disasters more frequent and severe across the entire state. Flooding is easily one of the worst and most deadly global natural disasters, responsible for millions of deaths over the last century¹. Floods also cause large amounts of long-term mental trauma, and the damage to infrastructure can take years and billions of dollars to rebuild^2-4. Severe flood events are shown to disproportionally affect at-risk and socially vulnerable communities, which adds complexity to implementing adaptation and mitigation strategies^5,6.

Floods can be categorized three ways: (1) river flooding when intense rainfall causes the water level to exceed the bank’s capacity, (2) surface (flash) flooding when the ground cannot drain rainfall faster than it accumulates, and (3) coastal flooding where high winds from hurricanes blow seawater inland in surges⁷. All three types of floods are known to occur in Texas, most significantly impacting urban areas with extensive impervious surfaces that preclude infiltration, especially those along the Gulf Coast^1,8. Over 1,000 square miles in Texas are below 5 feet of the tideline without any barrier protection, with 2,400 square miles being below 10 feet, exposing over 365,000 people directly to coastal floods⁹.

Hurricane Harvey in 2017 was the most intense rainfall event in the United States on record, causing over 100 deaths and $125 billion in damages¹⁰. Warmer temperatures from climate change made floods from Hurricane Harvey 15 percent more intense and three times as likely to happen^11,12. From 1950 to 2005, Texas had the largest number of inland flood-related deaths in the United States¹³. The largest number of tidal floods along the Texas coastline were recorded in 2020¹⁴. 

The occurrence of extreme rainfall events in Texas is projected to continue becoming more intense and frequent^1,15. As average air temperatures increase, the atmosphere’s capacity to hold water vapor rises by 7 percent per 1°C (1.8 °F), so more rain falls in the same period¹⁶. This increase in rainfall intensity puts drainage and flood management infrastructure under strain^7,17.

Rising sea levels increase storm surges from hurricanes, causing severe floods even if the hurricane fails to make landfall^15,8. The increased frequency of extreme rainfall events is expected to make urban floods in Texas 30 to 50 percent more likely to happen in the next two decades than in the last half of the 20th century^15,18. Models exploring a future with continued greenhouse gas emissions project a significant intensification of inland surges¹. Coastal floods are 33 percent more likely to have a 10 percent chance of occurring during any year by 2050^1,19.

Flood occurrence and magnitude for inland Texas rivers are expected to regionally increase over time as greater rainfall intensity outweighs drier soils with higher water capacities^15,20. Urban expansion along riparian corridors may elevate flood risk depending on infrastructure design, but coastal areas will be at an overall much greater risk^8,17,20. The United States faces a 26 percent greater risk of flooding over the next 30 years⁶. As populations in Texas continue to grow and urban areas expand, more people will be threatened by flooding, especially as coastal areas are desirable to live in and more affordable land often corresponds to lower floodplains with greater risk^20-23.

Floods are complex as they depend on weather conditions and location, surface position, and infrastructure design. The best way to prepare for flood events is to learn more about them and what flood risk zone you live in. Explore more about flood risk and climate change through the resources below.

Updated Flood Damage Risk Maps (The Conversation)

Vulnerability and Adaptation to Climate Change: An Assessment of the Texas Mid-Coast