Entitlement guide
Floodplain.
One parcel can have three different floodplain lines. The one that governs is not always the one on the FEMA map you found online.
The short answer
The FEMA flood map is the starting point. It shows the 1 percent annual chance floodplain, often called the 100-year floodplain, and in many places a floodway where building is most restricted.
In 2018, the federal Atlas 14 study raised design rainfall for much of Central Texas. Many cities and counties now regulate to updated local floodplains or higher elevations while new maps are prepared. Preliminary FEMA maps can also be on the way.
Flood rules adopted under the federal flood program are generally not protected by vesting in Texas. A new map can apply to a project already in review. That is why we show every relevant line, not just one.
- FEMA effective and preliminary flood maps
- Local regulatory or Atlas 14 based floodplains
- Floodway on or next to the site
- Share of the parcel affected and where it falls
- Freeboard and permit rules for the jurisdiction
Why it can stop a deal
Where projects get caught.
The governing line moved
A local regulatory floodplain or a preliminary map can be wider than the effective FEMA map. Building pads, parking and access can end up inside it.
The floodway leaves little room
Development in a floodway usually must show no rise in flood levels. That can take a study and still leave little usable land.
Elevation drives cost
Required finished floor elevations above the flood level can mean fill, taller foundations and drainage work, plus permits for each.
How it works
How it usually works in Central Texas.
Rules differ by city, county and utility, and they change. Treat this as orientation and confirm with the approving authority.
The maps
FEMA publishes effective Flood Insurance Rate Maps and, when a restudy is underway, preliminary maps. Local floodplain administrators can regulate to the best available data. In parts of Central Texas that means an interim floodplain or an Atlas 14 based line that is wider than the effective map.
Floodplain development permits
Work in a regulated floodplain usually needs a floodplain development permit from the city or county floodplain administrator. Requirements often include an elevation certificate, a minimum finished floor elevation above the base flood elevation, and limits on fill.
Freeboard
Freeboard is extra height above the flood elevation. Many Central Texas jurisdictions require one or two feet, and some measure from a more conservative flood line. Your engineer confirms the exact target.
Changing the map
A Letter of Map Change can correct or revise a FEMA map. A conditional letter, a CLOMR, reviews a proposed project before construction, and a LOMR revises the map after. These take engineering and FEMA review time, so they belong in the schedule early.
Vesting
Texas vesting law exempts floodplain rules adopted under the federal flood program. Plan for the strictest current line, not the line that was in effect when the land was bought.
Who decides
The people and offices involved.
| Who | What they decide |
|---|---|
| City or county floodplain administrator | Floodplain development permits and the regulatory line |
| FEMA | Map revisions through a CLOMR or LOMR |
| Your civil engineer | Flood studies, elevations and the no-rise analysis |
| Your surveyor | Ground elevations and elevation certificates |
- Which floodplain line does this jurisdiction regulate to today?
- Are preliminary FEMA maps or a local restudy coming?
- Is any part of the site in a floodway?
- What finished floor elevation will be required?
- Can the building, parking and access stay outside the line?
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