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Floodplain Regulations

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How Harris County’s amended floodplain regulations will affect commercial real estate

Floodplain regulations in Harris County. The Harris County Engineering Department approved an amendment to its Regulations for Floodplain Management on December 5, 2017, effective January 1, 2018. The new building code regulations include all construction projects within the 100-year floodplain requiring a permit, located in unincorporated areas of Harris County. The regulations are excluded from any area within city limits, such as Houston.

The new Harris County building code, which is one of the nation’s strictest, requires all-new construction in the 100-year floodplain to be built at least 24 inches above the 500-year floodplain elevation. Before, Harris County required that structures in the 100-year floodplain be built 18 inches above the 100-year floodplain.

A floodplain is an area at risk for flooding from a bayou, creek, or other waterway overflowing during certain flooding events. Areas in the 100-year floodplain have a 1% chance of flooding and areas in the 500-year floodplain have a .2 percent chance of flooding every year, according to the Harris County Flood Control District.

The amended regulations divide the permitting process into Class I and Class II.

  • Class I is issued for any development that is located on a property where the elevation of the ground is above the 1% or 100-year elevation.
  • A Class II permit is issued for any development that is located on a property where the ground elevation is below the 1% or 100-year flood elevation. 

Furthermore, both Class I and II permits have raised the minimum finished floor elevation required by the county. Class II permits will now require beam and pier foundations and additional wind speed design requirements. As a result, there will no longer be slab-on-grade foundations, which previously were an industry standard. Slab-on-grade foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. If a development is within the floodplain, there are methods of removing it from special flood hazard area. A pre-construction LOMR-F can allow for a Class-I permit, which would allow the developer to use a slab on grade foundation and avoid the cost of pier and beam construction.

Additionally, mechanical and electrical units will also have to be elevated to the level of the first floor. Critical facilities such as schools and hospitals are required to be elevated three feet above the 500-year floodplain or 24” above the centerline of the adjacent street, whichever is higher. Lastly, detention requirements remain the same in the new guidelines.

Amending the building code is a beginning point while waiting for the Federal Emergency Management Agency (FEMA) to modify the federal maps that determine the 100-year and 500-year floodplains, a process that could take years. Updated FEMA floodplain maps didn’t arrive until seven years after 2001’s Tropical Storm Allison.

Harris County, with a population of 3.6 million, is the third-most populous county in the United States. There are 34 municipalities within the county, including the City of Houston. Over 1.2 million people live in Unincorporated Harris County and rely on the county to be the primary provider of basic government services.

Below is the Harris County Engineering Department before-and-after cheat sheet.

Link to Regulation of Harris County, Texas for Flood Plain Management: http://www.eng.hctx.net/Portals/33/Publications/FPMRegs120517.pdf

Houston Commercial Real Estate Market Insight Harris County's Amended Floodplain Regulations 2018

Houston Commercial Real Estate Market Insight Harris County's Amended Floodplain Regulations 2018


Leta Wauson
Director of Research
leta.wauson@naipartners.com
tel 713 275 9618

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