The Harris County Commissioners Court on Tuesday is poised to make significant changes to the way the county regulates new development, including imposing a slew of new restrictions in Hurricane Harvey's wake that officials say are necessary to reduce flooding damage in the future.
The court would, for the first time in two decades, increase the amount new homes must be elevated to avoid floodwaters up to 8 feet higher than previously required in some flood-prone parts of the county. The regulations also would, for the first time ever, impose regulations in a 500-year floodplain instead of the 100-year floodplain.
If approved, the new rules would take effect Jan. 1.
"If we didn't do this, a new person could go out and build a house at an elevation that we know would have flooded during Harvey, and that doesn't make much sense," said County Engineer John Blount on Monday.
A 100-year event refers to a storm so severe that it has a 1 percent chance of occurring in any given year and equates to between 12 and 14 inches of rainfall in a 24-hour period across the county. A 500-year event has a 0.2 percent chance of occurring in any year and equates to between 17 and 20 inches of rainfall in 24 hours.
Floodplains and flood levels are mapped by modeling how water spills out of the creeks, bayous and ditches during those storms and how high the water would rise. For the more severe 500-year storm, water spills out in much wider areas.
For most areas across the county, Harvey was at least a 500-year event, and it was above a 1,000-year storm in many areas.
The proposals come nearly three months after Harvey devastated the county, dumping more than 51 inches of rain, flooding hundreds of thousands of homes and other buildings, and killing dozens of people.
The regulations would focus on the booming unincorporated region, not areas within Houston city limits. Unincorporated Harris County has added nearly 1 million people since 2000.
For some areas along the San Jacinto River, Spring Creek and Cypress Creek, the difference between the new and old regulations -- 500-year versus 100-year flood levels -- could be several feet of elevation required for new homes, which could increase the cost of development by thousands of dollars.
The proposed regulations also include measures to make elevation requirements even more stringent in floodways -- channels where water is expected to flow during floods -- as well as reinforcing new homes for high wind speeds.
Precinct 2 Commissioner Jack Morman said he "strongly supported" the proposal.
"We will have to combine that effort with major improvements to floodwater detention, bayou drainage and regional cooperation for it to make a difference in the immediate future," he said.
The Greater Houston Builders Association, Houston Real Estate Council, American Council of Engineering Companies of Houston, Houston Apartment Association and the Houston chapter of the American Institute of Architects have written letters to the count supporting the regulations.
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