How do Harris County’s Amended Floodplain Regulations Affect You?

February 15, 2018 by Shaun Theriot-Smith

The unprecedented flooding damage of Hurricane Harvey spurred jurisdictional authorities to get to work reviewing their floodplain regulations and Harris County is one of the first to release their latest changes. The County is keeping their word on raising the regulatory floodplain from the 100-year to the 500-year floodplain elevation and, in some areas, could reflect a difference of as much as several feet and many thousands of dollars in increased development cost.

The Harris County Engineering Department drafted and approved an amendment to its Regulations for Floodplain Management on December 5, 2017 and will be effective as we ring in the new year on January 1, 2018. These modifications reflect the effort of the County to create subdivision and permitting regulations that help prevent or mitigate flooding in our communities.

Floodplain Permitting

When a development is proposed within an unincorporated area of Harris County or in some Extraterritorial Jurisdiction (ETJ) of cities within the County, it must be considered for a Harris County floodplain development permit. There are two types of floodplain permits:

  • Class “I” Permit: Development that will be made on land that is located entirely out of the mapped 1% or 100-year floodplain as delineated on a FEMA Flood Insurance Rate Map (FIRM). This permit does not typically carry many additional requirements, as any structure will be above the regulatory floodplain.

Class “II” Permit: Development that is located on a property where any ground elevation is below the 1% or 100-year floodplain flood elevation. This permit requires that structures be elevated at a particular elevation above the regulatory floodplain.

So what are the changes?

Harris County Floodplain Regulation Update 2018
Click on the image above to download a PDF.

Subdivisions and Platting

A new designation has been created for parcels that conform with specific infrastructure criteria. During the platting process, if a parcel is above the 100-year floodplain and the infrastructure servicing the site, such as roadways and utilities, follow specific County infrastructure regulations regarding drainage design, then it is considered a “Conforming Subdivision”.

Class I Permit

If your development qualifies for a Class “I” Permit, or if your property lies entirely out of the mapped 100-year floodplain, then no significant changes have been proposed. If your property is within the Shaded X, or 500-year floodplain, it must be demonstrated that the lowest adjacent grade of the structure is above the 100-year floodplain.

If the development lies within a Non-conforming Subdivision, the structure must be 6” (12” for single family) higher than the lowest adjacent grade to the structure and at least 12” above the centerline of the adjacent street. Additionally, if a development within a non-conforming subdivision is under the 500-year floodplain and above the 100-year, then the finished floor elevation of the structure must be elevated above the 500-year floodplain elevation.

Class II Permit

Developments in this classification will be held to a much higher standard. Structures will be required to be constructed with pier and beam foundations. For a structure to be permitted in any Zone “A” or “V”, its lowest finished floor will be required to be elevated 24” above the 500-year flood elevation or 12” above the centerline of the nearest public street, whichever is higher. Mechanical, HVAC, and electrical equipment as well as storage tanks, pipes, and ducts must also now be elevated 24” above the 500-year floodplain. Previously only 18” above the 100-year floodplain elevation was required.

Additionally, critical facilities such as schools, hospitals and the like are required to be elevated three feet above the 500-year floodplain or 24” above the centerline of the adjacent street, whichever is higher.

When the property is within the regulatory floodway, the lowest horizontal supporting member of the structure must be elevated 36” above the 500-year floodplain on pier and beam; previously it was only 18” above the 100-year floodplain elevation. Similarly, developments located in Zone “V”, or coastal areas affected by flooding caused by wave-action, must have its lowest supporting structural member elevated 36” above the 500-year floodplain by pier and beam.

In Zone “AO”, where the risk of flooding is caused by positive sheet flow rather than raising floodwaters, a depth number is determined by FEMA. Properties in this zone must have finished floor elevations 36” above this depth number. If no depth number is assigned in Zone “A”, then the finished floor must be elevated to 6 feet higher than the highest adjacent grade.

Inspections

Typically, only Class “II” permitted developments are required to have an Engineering certification and elevation certificate prior to construction, but with this change any Class “I” permitted properties within Non-Conforming Subdivisions will also require a similar inspection.

Harris County Amended Floodplain Regulations

What’s Next

With the approval of the Commissioner’s Court and the County Engineer, these regulations go into effect January 1, 2018. Many developers and residential development organizations have also voiced support for this change, citing the increased safety and welfare of future developments from flooding.

If your 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 development to use a slab on grade foundation and avoid the cost of pier and beam construction.

Many cities in this area use or draw from the Harris County development criteria in lieu of their own floodplain regulations and may update their own to reflect similar changes. The City of Houston has not yet proposed new criteria, but officials have indicated that matching the new County criteria is being considered. Their current floodplain criteria only require a structure to be 12” above the 100-year floodplain — significantly lower than the changes described here.

If you have a development within Harris County and have questions about the floodplain regulations that apply to your property, contact our floodplain permitting experts at BIG RED DOG at 1-877-733-3642 and we will walk you through the process.

This post was originally published on Building Bayou City.

Written by Shaun Theriot-Smith

Shaun Theriot-Smith

Shaun Theriot-Smith is a Project Engineer in our Houston office. Shaun graduated from The University of Houston with a Bachelor of Science in Civil Engineering. He enjoys spending time with his wife and twin daughters.