A Houston Public Works analysis of homes inundated by Hurricane Harvey in the city’s floodplains says 84 percent of the structures would have been spared if they had been built to the more stringent standards Mayor Sylvester Turner plans to put to a City Council vote later this month.
The data was distributed to council members for the first time Friday, six weeks after Turner outlined his proposal and roughly a week after the end of the city’s announced period for public feedback.
Public Works spokeswoman Alanna Reed said staff still were gathering data when the proposal was first announced, adding that efforts to verify its accuracy continued through Monday, when the department released updated figures that differed slightly from those released Friday.
“This data, there’s a lot of little details to it, there are a lot of variables,” she said. “They just want to make sure, as I do, that it’s the most accurate data that’s out there.”
Of the 31,822 flooded single-family homes Public Works examined, an estimated 48 percent of them would not have flooded during Harvey if all of them had been built to the city’s current elevation standard, which was set in 2006.
That rule requires that new or redeveloped homes sit one foot above the projected water level in a 100-year flood (also known as a storm that has a 1 percent chance of happening in any given year).
Public Works also ran scenarios based on the larger 500-year floodplain and the depth of floodwaters during a 500-year storm, which has a 0.2 percent chance of flooding in any given year.
If the homes Harvey flooded had been elevated to the projected water level in a 500-year storm, 56 percent would have been spared, the report states. Make them a foot higher than that, and 72 percent would not have flooded.
Placing the homes two feet above the 500-year flood level — the standard Turner is proposing — would have saved 84 percent of the homes.
Going even higher — to the 500-year flood level plus three feet — would have spared 93 percent of the homes analyzed.