Harris County toughens regulations on construction after Hurricane Harvey, including higher builds

A neighborhood is inundated by floodwaters from Tropical Storm Harvey on Tuesday, Aug. 29, 2017, in Spring. A neighborhood is inundated by floodwaters from Tropical Storm Harvey on Tuesday, Aug. 29, 2017, in Spring. Photo: Brett Coomer, Houston Chronicle Photo: Brett Coomer, Houston Chronicle Image 1 of / 75 Caption Close Harris County toughens regulations on construction after Hurricane Harvey, including higher builds 1 / 75 Back to Gallery

The Harris County Commissioners Court voted unanimously on Tuesday to make significant changes to the way the county regulates new development, including a slew of new restrictions in Hurricane Harvey's wake that officials say are necessary to prepare the Houston area for future flooding events.

The regulations will, 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 new rules also would, for the first time, impose regulations in a 500-year floodplain instead of a 100-year floodplain.

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The regulations would go into effect Jan.1.

A 100-year event refers to a storm so severe that it has a 1 percent chance of occurring in any given year, and would equate 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 would equate 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.

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The newly proposed regulations focus on the booming unincorporated region as opposed to areas within Houston city limits. Unincorporated Harris County has added nearly 1 million people since 2000.