What Is a Flood Map Revision and How Does It Affect My Land?
Key Takeaways
- A Letter of Map Revision is FEMA's tool for physical changes, not simple mistakes: LOMRs are generally based on physical measures that affect the hydrologic or hydraulic characteristics of a flooding source, and can modify the regulatory floodway, the Base Flood Elevations (BFEs), or the Special Flood Hazard Area (SFHA), according to FEMA.
- You get a 90-day window to appeal before a new flood map becomes final: FEMA provides a 90-day appeal and comment period on new or revised BFEs, flood zones, or floodway boundaries, and a finalized map still carries a six-month compliance period before it takes effect, according to FEMA's Community Members' Guide.
- A mapping error and a physical change get fixed differently: a Letter of Map Amendment (LOMA) corrects land always on natural high ground, a Letter of Map Revision Based on Fill (LOMR-F) covers land raised above the BFE with fill, and FEMA states it normally issues a determination within 60 days of a complete application.
What Is a Flood Map Revision and How Does It Affect My Land?
A flood map revision is FEMA's formal update to a parcel's flood hazard designation — most often a Letter of Map Revision (LOMR) triggered by a physical change to a flooding source, or a smaller-scale Letter of Map Amendment (LOMA) or Letter of Map Revision Based on Fill (LOMR-F) that corrects how an individual parcel was originally mapped, according to FEMA. This guide covers that map-change process specifically — what triggers it, what it can alter, how long it takes, and how to check or contest one. If your parcel's flood-zone status is already settled and you want to sell it as-is, see how to sell land in a flood zone; if your ground is simply, physically wet regardless of any map, see how to sell swamp or bottomland that floods. For more, visit our blog.
Why Did My Land Suddenly End Up in a Flood Hazard Area?
Most owners who discover their parcel is newly in a Special Flood Hazard Area (SFHA) got there one of two ways: the community completed a broader restudy that produced a new or updated Flood Insurance Rate Map (FIRM), or a Letter of Map Revision changed the floodway or Base Flood Elevation nearby in a way that pulled neighboring ground into the SFHA, according to FEMA. Neither means you did anything wrong.
Community-wide restudies happen because flood risk changes: FEMA notes that water flow and drainage patterns shift over time due to environmental change and development, and older maps, some based on decades-old studies, may not reflect the current picture. When FEMA and a community complete a restudy, they issue a preliminary flood map first, hold public review, and only finalize it after the appeal process described below — a parcel doesn't move into an SFHA without a public review step somewhere in its history.
The other path is a LOMR: FEMA states these are generally based on physical measures — a new culvert, channel modification, a levee, fill placed for a development project — that change the hydrologic or hydraulic characteristics of a flooding source. A LOMR triggered by a neighboring project can expand a mapped floodway or SFHA boundary onto parcels that never had construction on them at all.
What Can a Letter of Map Revision Actually Change on My Parcel?
A LOMR can modify three specific things on the official flood map: the regulatory floodway, the effective Base Flood Elevations (BFEs), and the Special Flood Hazard Area (SFHA) boundary, according to FEMA's LOMR glossary entry. It does this by letter rather than by physically reprinting the map panel, which is what separates it from a full Physical Map Revision (PMR).
- The floodway is the river channel plus adjacent land that must stay clear to carry the base flood without raising water levels beyond a designated height — the most restricted part of any flood-mapped parcel.
- Base Flood Elevation (BFE) is the projected height floodwater reaches in a 1-percent-annual-chance ("100-year") event; a LOMR can raise or lower the BFE that applies to your parcel.
- The SFHA boundary is the line FEMA draws around the area subject to that flood — where the mandatory flood insurance purchase requirement is triggered, according to FEMA.
- A LOMR is accompanied by the revised map portion, flood profiles, and floodway data tables, and becomes part of the community's public record.
- FEMA's LOMR guidance states a community or individual can request one, but it must be made in writing through the community's Chief Executive Officer (CEO), or an official the CEO designates, because the community adopts the revised information into its own floodplain ordinances.
How Long Does a Flood Map Revision Take, and Can I Appeal It?
Yes, but only during a specific window: FEMA provides a 90-day appeal and comment period after a preliminary flood map is released, and the path from preliminary map to an effective new FIRM runs through several more defined stages, according to FEMA's Community Members' Guide.
For a community-wide restudy: preliminary map issued; community open house; a 90-day appeal and comment period to challenge a new or modified BFE, SFHA boundary, or floodway with scientific evidence; FEMA resolves all appeals; the community receives a Letter of Final Determination (LFD) stating the map becomes effective in six months; then the new FIRM takes effect.
For the letter-based tools: a Physical Map Revision (PMR) — reprinted map panels — includes its own comment and six-month compliance period, and can take as long as 18 months, per FEMA. A LOMR is explicitly faster and cheaper than a PMR since it revises by letter instead of reprinting the panel, but FEMA publishes no fixed day count — only that it "typically takes less time and is less expensive than a PMR." A LOMA or LOMR-F determination moves fastest: FEMA normally issues a completeness notice within 30 days, and a determination within 60 days of receiving all required data.
Check an active request's status through your community's floodplain administrator.
My Land Was Mapped Into the Flood Zone by Mistake, or the Ground Was Filled — What's the Difference Between a LOMA and a LOMR-F?
The distinction comes down to whether the map was wrong about existing conditions or conditions actually changed: a LOMA corrects land that was always naturally high enough to be outside the flood zone, while a LOMR-F applies to land artificially raised above the flood elevation using fill, according to FEMA. Both are narrower, cheaper tools than a full LOMR.
FEMA explains that because of scale or topographic limitations in FIRM source data, small areas of genuinely high ground sometimes get shown inside the SFHA by mistake — an "inadvertent inclusion." A LOMA is FEMA's fix for that: it officially establishes that a property sits outside the SFHA because it's on natural ground at or above the Base Flood Elevation. A LOMR-F covers a different situation — earthen fill was placed on the parcel, during or after the original engineering study, that raised it above the Base Flood Elevation.
Here's how the three tools compare:
| Letter of Map Revision (LOMR) | Letter of Map Amendment (LOMA) | Letter of Map Revision Based on Fill (LOMR-F) | |
|---|---|---|---|
| What triggers it | A physical change to a flooding source — a culvert, channel work, a bridge, a levee, or a development project — that alters the floodway, BFE, or SFHA boundary | The parcel was always on natural high ground above the BFE but got mapped into the SFHA anyway (an "inadvertent inclusion") | The parcel was raised above the BFE using placed earthen fill, not natural elevation |
| Who files it | Requested through the community's CEO or a designated floodplain official; FEMA notes a community or individual can initiate the request | An individual owner, renter, or lessee can submit directly to FEMA | An individual owner, renter, or lessee can submit directly to FEMA, through the same channel as a LOMA |
| What it changes | Can modify the effective floodway, Base Flood Elevations, and/or the SFHA boundary on the official map itself | Removes a specific property or structure from the SFHA designation — corrects the map, doesn't alter ground conditions | Removes the filled area from the SFHA designation, conditioned on the fill meeting FEMA's elevation standard |
| What the owner needs | Engineering/hydraulic data and MT-2 forms; FEMA charges a review fee for requests involving structural measures | An Elevation Certificate from a Licensed Land Surveyor or Registered Professional Engineer; no FEMA review fee | An Elevation Certificate showing the fill elevation; FEMA charges a review and processing fee |
Who Actually Files a LOMR or LOMA, and What Should I Do First?
The filing party depends on which tool applies: a LOMR generally goes through the community's Chief Executive Officer or floodplain administrator, while a LOMA or LOMR-F can be submitted directly by an individual owner, renter, or lessee, according to FEMA. Your practical first steps are the same either way.
- Pull your parcel's current FIRM panel. Use the FEMA Flood Map Service Center (msc.fema.gov) to look up the effective flood zone designation and panel number.
- Talk to your local floodplain administrator. Usually a city/county engineer, planning director, or zoning administrator, according to FEMA — they hold the community's flood maps and correspond with FEMA as a request moves through review.
- If elevation is the question, get an Elevation Certificate. Both LOMA and LOMR-F requests require elevation data certified by a Licensed Land Surveyor or Registered Professional Engineer, according to FEMA — the document establishing whether your ground, or your fill, sits at or above the Base Flood Elevation.
- Use the correct form. FEMA's MT-EZ form covers a LOMA for a single residential lot or structure; the MT-1 package (or FEMA's Online LOMC tool) covers larger LOMA and all LOMR-F requests; a LOMR uses MT-2 forms submitted through your community.
What Does This Remap Actually Mean for Me — Insurance, Permits, and Selling?
A remap into an SFHA has three concrete effects: it can trigger a lender's mandatory flood insurance requirement if you have a federally backed mortgage, it puts any future construction under your county's floodplain permitting rules, and it becomes something you're expected to disclose if you sell. None of the three change what the ground physically is.
Insurance. Under the Flood Disaster Protection Act of 1973, flood insurance is required as a condition of federal or federally backed financial assistance when the property secures that assistance and sits in a designated SFHA, according to FEMA. Without a federally backed mortgage, that mandate doesn't apply directly. Premiums under FEMA's Risk Rating 2.0 methodology are calculated per parcel based on its own risk characteristics, so confirm actual cost with your insurer or the National Flood Insurance Program rather than any generic figure.
Permitting. A parcel inside a mapped SFHA or floodway falls under your community's floodplain management ordinance for future development, and FEMA requires communities to regulate floodway development to prevent any increase in upstream flood elevations. Check with your floodplain administrator before planning any grading, fill, or construction.
Selling. This is where a map revision differs from two related situations we cover elsewhere, and it's worth being precise about which applies to you. If your parcel's flood-zone designation is already settled and you're weighing how to sell it as-is, that's our flood-zone selling guide — financing barriers, disclosure obligations, who actually buys flood-zone land. If your land is chronically, physically wet — swamp, river bottom, seasonal flooding — regardless of what any map says, that's selling swamp or bottomland that floods. This guide sits upstream of both: it's about the map itself, not the dirt or the sale. Buyers and lenders react to the designation on file, not to a change in the actual land, which is exactly why confirming or correcting a bad designation is worth doing before you assume the worst.
Thinking About Selling Instead of Fighting the Map?
If the appeal window has closed, the designation is accurate, or you'd simply rather not spend months on elevation certificates and floodplain administrator calls, a direct sale is still available to you. Jerez Land buys parcels regardless of flood-zone designation, reviews each one's specific situation, and issues an individually priced, firm written offer — no formula, no percentage-of-value calculation, and no financing contingency to wait on, because we absorb the carrying costs, marketing expense, and resale risk ourselves. Request a no-obligation review of your parcel and we'll tell you where you stand. For more on how direct buyers operate and how to vet one, see are we buy land companies legit, and for a broader sense of what goes into valuing a parcel, see how much is my land worth.
Frequently Asked Questions
My 20 acres just got remapped into a flood zone and I don't have a mortgage — do I have to buy flood insurance?
No federal law forces you to buy flood insurance just because your land moved into a Special Flood Hazard Area — the mandatory purchase requirement under the Flood Disaster Protection Act of 1973 only attaches when the property secures a federally backed loan, grant, or other federal assistance, according to FEMA. Without a mortgage, insurance is optional, though flood risk isn't eliminated, and any future construction still falls under your county's floodplain development permitting rules.
My land shows up inside a floodway on the new preliminary map — can I fight it before it becomes final?
Yes. FEMA provides a 90-day appeal and comment period after a preliminary flood map is released, during which you can file a formal appeal against a new or modified Base Flood Elevation, Special Flood Hazard Area boundary, or floodway if you have scientific or technical evidence the mapping is incorrect, according to FEMA's Community Members' Guide. Appeals go through your community's floodplain administrator rather than directly to FEMA, and afterward FEMA resolves every appeal before sending the community a Letter of Final Determination.
My parcel was filled with dirt years ago and sits above the flood elevation — how do I get it removed from the flood zone?
That's the Letter of Map Revision Based on Fill (LOMR-F) route: FEMA's LOMR-F process removes land from the Special Flood Hazard Area when it's been raised above the Base Flood Elevation with placed fill, according to FEMA. You'll need a Licensed Land Surveyor or Registered Professional Engineer to prepare an Elevation Certificate showing the fill elevation, and FEMA charges a review fee for LOMR-F requests, unlike the fee-free Letter of Map Amendment process for land that was always naturally high.
What's actually the difference between a LOMA and a LOMR?
A Letter of Map Amendment (LOMA) corrects a mapping mistake — it applies when a property was always on natural high ground above the Base Flood Elevation but got mapped into the Special Flood Hazard Area anyway, according to FEMA. A Letter of Map Revision (LOMR) is different: it applies when conditions on the ground have physically changed, such as a new culvert or channel work, and can modify the actual regulatory floodway, Base Flood Elevations, or the SFHA boundary, rather than just correcting how one parcel was drawn.
I bought this land last year and now the county says it's in the floodway — did something get missed at closing?
Not necessarily. Flood maps get revised independently of any individual sale — a Letter of Map Revision can modify the floodway or Special Flood Hazard Area boundary based on physical changes to a flooding source that happened after your closing, according to FEMA. Pull your parcel's current FIRM panel at the FEMA Flood Map Service Center and ask your floodplain administrator when the revision took effect relative to your purchase date before assuming anything was missed.
Does a flood map revision permanently reduce what my land is worth?
A flood map revision changes the regulatory picture on a parcel — insurance requirements, floodplain permitting, and buyer financing options — but it doesn't change the physical ground itself, and land in a Special Flood Hazard Area still sells to buyers who don't need lender financing or federally backed insurance. Jerez Land reviews each parcel's specific flood-zone status and issues an individually priced, firm written offer rather than a formula, so the fastest way to know where you stand is to request a review of your specific parcel.
Disclaimer: This article is for informational purposes only and does not constitute legal, financial, engineering, or professional advice. Floodplain rules, permitting, and appeal procedures are administered locally and vary by community; confirm current requirements with your county or municipal floodplain administrator before relying on anything here. Always consult qualified professionals — a licensed surveyor, engineer, or real estate attorney — before making decisions about a flood-mapped parcel. Jerez Land is not responsible for actions taken based on this information.