A new Texas flood plan that estimated 5 million Texans lived in flood-prone areas may already be outdated because it did not take into account new trends and climate change, experts say.
This new plan, developed by the Texas Water Development Board (TWDB), used existing flood data, but there were regions where data didn’t exist or was outdated. It is estimated that more than 5 million Texans live or work in flood-prone areas. These areas are identified based on historical averages that show a 1 percent annual chance of flooding, or the 100-year floodplains.
“It’s a useful statistic because it does reflect that particular region’s hydroclimate. But the concern is that it’s based on the assumption that the climate is not changing,” Rebecca Edwards, a doctor in atmospheric science and civil engineering told The Houston Chronicle.
“In addition to using that statistic, there was not a lot of specific mention in the plan of the potential for changes in precipitation going forward,” she said.
Cyrus Reed, a conservation director for the Lone Star Chapter of the Sierra Club said the modeling used for the plan to predict floods is outdated and does not include future climate variables.
“What we thought was a one in 100 chance of flood, or one in 500, they may be much more frequent than we were thinking because the climate is changing,” he told The Texas Tribune.
The plan assumes that Texas regions will be hit by storms at the same rate as the data provided, but some areas have been hit by storms more frequently in recent years.
“I personally know people across the city that are still recovering from Harvey or from other storms, and then they end up getting hit again,” Stephany Valdez, a water expert for the Coalition for Equity, Environment and Resilience told The Chronicle.
For example, during Hurricane Harvey, which caused 68 deaths and damaged over 204,000 homes, Houston experienced its third 500-year flood in three years, suggesting that current floodplain maps underestimate the city’s risk.
Multiple people submitted their comments for the plan, urging TWDB to incorporate new analyses into the plan now rather than waiting for the next revision in five years.
The plan is set to be adopted in September 2024, and includes 4,609 project proposals, including a coastal barrier to protect Houston region from storms. Together, these projects would cost about $54.5 billion.
