Greater Katy has seen flooding four of the last five years, the last three events being the Tax Day Floods of April 2016 as well as rain events on May 26 of both 2014 and 2015.
As urban sprawl moves outward from Houston, more impermeable surfaces, such as paved roads, driveways and roofs, change how water flows, said Mike Bira, an environmental scientist with the Environmental Protection Agency.
Surface water runoff from these impermeable surfaces causes flash flooding and changes in-stream functions, thus redefining flood zones.
“Normally, the land acts to absorb a certain amount of precipitation and release excess water slowly into streams,” Bira said.
As a result, the land changes faster than data is updated, making many flood zone maps out of date, Bira said. This can make it difficult to know if a specific property is vulnerable.
Diana Herrera, a regional flood insurance specialist with the Federal Emergency Management Agency, agreed with Bira’s assessment. She added the flood maps for Harris and Fort Bend counties were updated in 2014, while Waller County’s map is from 2009. The Harris and Fort Bend's latest maps are from 2014, while Waller's is from 2009.
FEMA updates flood maps as often as budgets allow, prioritizing those areas most prone to flooding, Herrera said. The maps show what is referred to as the 100-year flood plain, meaning that there is a 1 percent chance of flooding each year.
“During a 30-year mortgage, you’ve got a 26 percent chance of getting flooded at least one time [in a 100-year flood plain],” Herrera said.
Flood damage costs Americans $8.2 billion each year on average and just 1 inch of water inside a building can cause about $27,000 in damage, according to FEMA.
An estimated more than 95 percent of residential flood insurance is underwritten through FEMA’s National Flood Insurance Program, said Michael Barry, vice president of media relations for the Insurance Information Institute. The NFIP launched in 1968 to make flood insurance more affordable.
Private companies had walked away from flood insurance due to the underwriting and risk assessment challenges, Barry said. As it stands, the program is in debt.
Homeowners who have not experienced flooding recently are reluctant to purchase what they consider an unnecessary measure of protection, leading to a smaller risk pool than is necessary to keep the program solvent, Herrera said.
“FEMA’s NFIP owes the U.S. Treasury nearly $25 billion, primarily because of monies the NFIP had to borrow to meet its financial obligations to NFIP policyholders after 2005’s [Hurricanes] Katrina and 2012’s Sandy,” Barry said.
Congress is debating whether to continue the NFIP, which is set to expire Sept. 30, Barry said. Prices must be set to match flood risks and give the program a way to repay debt.
“Everybody’s subject to flooding. It just is at different risk levels,” Herrera said. “Buy flood insurance whether it’s through the federal government or through the private markets.”