Construction in the Flood Plain

• What is a Flood Plain?
• How do I find out if my lot is in a Flood Plain?
• What is a 100-year flood plain? a 25-year flood plain?
• Why do the flood plain maps change?
• Can I build on a lot in the 100-year flood plain? The 25-year flood plain?
• Are there special requirements in the flood plain?
• If I build an addition or deck outside my building, do I need to raise my existing building one foot above the 100-year flood plain?
• What is the penalty if I don't secure all of my approvals?
• Who can I see if I need additional information?

A flood plain is the area adjacent to a river, creek, lake, stream, or other open waterway that is subject to flooding when there is a significant rain. Flood plains can be entirely within the waterway.

You can request this information from the Comal County Engineers Office, located at 195 David Jonas Drive, off hwy 46.

If your property is in the 100-year flood plain, there is a 1-in-100 chance in any given year that your property will flood. If it is in the 25-year flood plain, there is a 1-in-25 chance in any given year that your property will flood. The statistical chance of flooding is not changed by any one flooding event; but repeated flooding may result in the flood plain being recalculated.

A 100-year flood plain is always wider than a 25-year flood plain, and the 25-year flood plain is contained within the 100-year flood plain.

Comal County works with the Federal Emergency Management Agency (FEMA) to update flood plain maps to show the areas that will flood during the 100-year flood in support of the National Flood Insurance Program.

The changes in flood plain maps reflect changes in land use (such as increased building activity), changes in the waterways, and flood control improvements (such as detention ponds or other flood control measures).

As more lots are covered with more buildings and parking lots, the amount of water that flows into creeks and lakes increases because there is less vegetation to absorb the water when it rains. This is one reason why buildings that were not originally built in a flood plain are now in the 25-year or 100-year flood plain.

If you wish to build a home or place a manufactured home in the 100-year flood plain and your lot was lawfully recorded September 25, 1983, you may file a permit application. You must also file a plot plan and submit building plans that shows compliance with all flood plain regulations as well as other County standards. When your site plan and building permit applications are approved, you can request a pre-construction conference and then begin constructing the improvements and requesting inspections. All construction that is allowed in flood plain areas must have the lowest floor elevation at least one foot above the 100-year flood plain.

There are special flood plain requirements in the code. The building, electrical, mechanical, and plumbing codes also contain special flood plain provisions. The plans prepared by your architect and engineer must show compliance with all of the standards that apply for your project.

The addition or new deck must comply with all flood plain standards. If the value of the addition and remodeling of the home or business exceeds 50% of the value of the existing home or business, the existing structure(s) must be elevated one foot above the 100-year flood plain or flood-proofed

• You would not be able to occupy or use your building or parking lot until you received all required permits and passed inspections.
• You could be fined.
• The City may tear down the improvements constructed without permits and inspections and you would be assessed the cost of the demolition.

The Development Assistance Center can help you or your architect or engineer obtain additional information about requirements for building in the flood plain.