Is my Austin lot in the floodplain? What the code requires to be mapped and shown
Austin has two floodplains, and they are not the same line
Read §25-7-33(D) and the same pair appears in every requirement:
- a 100-year floodplain; and
- a FEMA floodplain.
Listed separately, every time. They are not synonyms in this code. The FEMA floodplain comes off the federal flood insurance rate map. Austin's 100-year floodplain is calculated under the Drainage Criteria Manual — and where the two disagree, both still have to be shown.
For someone evaluating a lot, this is the practical point: checking the FEMA map and stopping answers half the question. The half Austin regulates development against is the other one.
What has to be depicted, by application type
The requirement scales with the application — but note where it does not stop:
| Application | Must depict |
|---|---|
| Preliminary plan or subdivision construction plan | 100-year floodplain · FEMA floodplain · drainage easement or proposed drainage easement |
| Final plat | Drainage easement · any portion of a FEMA floodplain outside a drainage easement |
| Site plan — including a site plan exemption or general permit | 100-year floodplain · FEMA floodplain · drainage easement |
| Residential building permit | 100-year floodplain · FEMA floodplain · drainage easement |
From §25-7-33(D). The obligation reaches a residential building permit and a site plan exemption — being exempt from site plan review does not exempt you from depicting the floodplain.
The city can make you go to FEMA
§25-7-33(C) is short and consequential. If the director determines that FEMA regulations require a request for a flood insurance rate map revision, the director may require that the revision request be submitted by the owner of property to be developed.
So a project that changes the mapped floodplain can carry a federal map-revision process as a condition — a timeline measured in months, run by the applicant rather than by the city.
A FEMA floodplain outside a drainage easement gets written onto the plat
§25-7-33(E) handles the awkward case: part of a FEMA floodplain falls outside any drainage easement. When that happens the owner must, on the final plat:
- Identify the portion of the FEMA floodplain lying outside the easement — expressly including the community and panel number of the flood insurance rate map; and
- Include a note that does three things:
- refers the reader to federal regulations governing development in a FEMA floodplain;
- states that flood insurance may be required; and
- describes efforts to revise the flood insurance rate map.
That second item is the one to notice if you are buying. The warning is recorded on the plat itself, which means it travels with the land and shows up in a title search. A buyer who reads the plat will see the flood insurance point before anyone has to raise it.
Common questions
Send us an address and we will tell you what we find
We do this research ourselves on every project we take on — zoning, floodplain, watershed, trees, whether it is a legal lot. Send us an address and we will run it and tell you what we find. It works the same whether you own a vacant lot, a house you are thinking of adding a unit to, or a house you are thinking of replacing. No charge and no strings, and if it is a bad lot we will say so.
Send us an addressWe are homebuilders, not the City of Austin. This page explains how we read the code in practice — it is not legal advice and it is not an official determination. Always confirm with Austin Development Services before you rely on it for a project. The authoritative text is the Austin Land Development Code; permitting questions go to Austin Development Services Department.