About 20% of the population live in an area susceptible to flooding, according to data gathered as part of a statewide effort to harden Texas against floods and rising sea levels. The analysis is part of the Texas Water Development Board’s first statewide flood plan which the Legislature required in a 2019 law passed in response to Hurricane Harvey.
Flood risks in Texas are increasing as climate change brings heavier precipitation, stronger hurricanes and sea level rise as the State’s population continues to climb. More than 2.4M Texans live in areas that have a 1% chance of flooding each year, known as the 100-year floodplain, the analysis found. Another 3.5M people live in areas with a 0.2% chance of flooding each year, known as the 500-year floodplain. One-fifth of the state’s land - roughly 56,000 square miles - now fall within the 100-year floodplain.
It will likely cost Texas tens of billions of dollars to protect people and property from floods. The first projects proposed in the plan add up to $38 billion, including the massive coastal barrier proposal with its “Ike Dike,” a huge gate system proposed for the mouth of Galveston Bay. As climate change worsens, higher global temperatures increase the amount of moisture in the air and thus the risk of extreme rainfall events, the Texas state climatologist and a national climate assessment have found. Heavier precipitation linked to climate change likely increased Hurricane Harvey’s total rainfall by as much as 19%, one study found. Almost 50 inches of rain fell in some areas of Houston during Harvey - the highest rainfall amount in a single storm for any place in the continental U.S.
At the same time, higher global temperatures are melting glaciers, increasing sea levels around the world and making coastlines more vulnerable to storm surges. Between 2000 and 2019, rising sea levels caused the Texas coastline to retreat about 4 feet per year on average, according to a 2021 University of Texas Bureau of Economic Geology report for the Texas General Land Office. The San Jacinto region has the most people living in a floodplain: almost 2.5M people are in a 100- or 500-year floodplain. The Lower Rio Grande region is next with about 1M people at risk.
During the 2023 legislative session, lawmakers allocated $625M to finance flood prevention projects through the Flood Infrastructure Fund. Once the statewide flood plan is finalized, projects will have to be included in the plan in order to access those funds. Another $550M of the surplus was allocated to the coastal barrier project that includes the Ike Dike.