Floodplain determinations and FEMA LOMR-F submittals

What a floodplain determination answers

We check the FEMA flood map for the site. In Texas, we also check the state's Base Level Engineering data where it exists. Then we tell you what the mapped zone means for your layout. It can shrink the usable area, raise the finished floor elevations or add a permit. Many sites need nothing more than this answer.

Who decides

• Your local floodplain administrator. In a community that takes part in the National Flood Insurance Program, building in a mapped floodplain needs a floodplain development permit from that office. In unincorporated Harris County, for example, the Office of the County Engineer requires one for all work in the floodplain.
• FEMA. FEMA decides any change to its map.
• We prepare the engineering and the request. We do not decide the outcome.

What a LOMR-F is

A Letter of Map Revision based on Fill (LOMR-F) is FEMA's change to the Special Flood Hazard Area on the flood map, based on fill placed outside the regulatory floodway. It can remove a property, a structure or both from the Special Flood Hazard Area. FEMA's tests:

• For a structure, the lowest adjacent grade must be at or above the base flood elevation.
• For a lot, the lowest point on the lot must be at or above the base flood elevation.
• The community must find that the land and any structures are reasonably safe from flooding.

The request is filed on FEMA's MT-1 forms or through FEMA's online Letter of Map Change application. FEMA charges a fee to review it.

If FEMA issues the LOMR-F, the federal flood insurance purchase requirement no longer applies to what it removed. A lender can still require flood insurance.

When it fits

• Your grading plan places fill to raise building pads or lots above the base flood elevation.
• The fill sits outside the regulatory floodway.
• The fill is in place.

A map change is not always needed or available. When the flood study itself has to change, that is a different FEMA request. We tell you which one your site needs.

What we do

1. Read the map. FEMA flood zones and panels, and Texas Base Level Engineering data where it exists.
2. Tell you what it means for the layout, the finished floors and the permits.
3. Coordinate with the floodplain administrator on the local permit.
4. Revise the grading plan so the fill reaches the elevation the request depends on. See site plans and grading plans.
5. Prepare the LOMR-F request on FEMA's MT-1 forms once the fill is in.
6. Answer FEMA's questions until it issues its determination.

Where the design depends on flood elevations, the work moves to a drainage study and HEC-RAS model update.

What you get

• A written floodplain determination: the mapped zone and what it means for your site.
• A revised grading plan that places the fill.
• The LOMR-F request on FEMA's MT-1 forms, with the data behind it.

What affects time and cost

• The map and the BLE data. Some sites are clear from the map alone.
• The floodway. A LOMR-F covers fill outside the regulatory floodway.
• The survey. The determination starts from your boundary and topographic survey, and the request depends on the elevations of the fill once it is in.
• The community. The local floodplain administrator sets the local permit and must find the land reasonably safe from flooding.
• FEMA. FEMA sets its fee and review time and decides the request.