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LOMA and LOMR-F guidance

Glossary

Letter of Map Revision (LOMR)

A LOMR is FEMA's official revision to a flood map, changing flood zone boundaries or Base Flood Elevations.

A Letter of Map Revision, or LOMR, is FEMA's process for officially changing the flood map itself — updating zone boundaries, Base Flood Elevations, or floodway limits. Unlike a LOMA, which is property-specific, a LOMR actually alters the published Flood Insurance Rate Map for a community.

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Key takeaways

A LOMR changes the official FEMA map, not just a single property's status.
LOMRs are typically requested by communities, developers, or engineers after physical changes like channel improvements or levee construction.
The process is more complex, expensive, and time-consuming than a LOMA.
A LOMR requires detailed hydrologic and hydraulic engineering analysis.

Why it matters

When large-scale drainage improvements or development projects change flood conditions, the map needs to be updated to reflect reality.
Homeowners in the affected area may benefit from reduced flood zones or updated BFE values after a LOMR is processed.
Understanding LOMR vs. LOMA helps homeowners know which process applies to their situation.

Frequently asked questions

How is a LOMR different from a LOMA?

A LOMA is a property-specific determination saying the existing map was wrong for that parcel — the ground was always high enough. A LOMR is a formal revision to the map itself, usually because physical conditions have changed (such as a new drainage channel or levee). A LOMR changes the map for an area; a LOMA addresses a single property without changing the map.

Can a homeowner request a LOMR?

Technically yes, but in practice LOMRs are almost always submitted by communities, developers, or engineering firms because they require detailed hydraulic studies and significant technical documentation. The cost and complexity are far beyond what a typical homeowner would handle. Most homeowners are better served by a LOMA or LOMR-F.

How long does a LOMR take to process?

A LOMR can take six months to over a year to process, depending on the complexity of the engineering analysis and any back-and-forth with FEMA reviewers. This is significantly longer than a LOMA, which typically takes about 60 days.

Does a LOMR cost money?

Yes. FEMA charges a review fee for LOMR applications, and the applicant must also pay for the required engineering studies and documentation. Total costs can range from several thousand to tens of thousands of dollars depending on the scope of the revision.