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Navigating Flood Map Changes: LOMAs, LOMRs, and more

April 3, 2024
Meghan Finlayson

Many of the community partners we work with are proactive about implementing flood map changes. Making changes that incorporate updated topographic information, new modeling techniques, and/or physical changes in the landscape provides more accurate data on their flood risk, and enables them to implement more effective policies and make more informed decisions to improve their community’s resilience.

However, navigating through these map changes can be complex and nuanced, leading to many questions and uncertainties. In some cases, these challenges even deter certain communities from pursuing the map changes altogether. 

In this blog, we’ve outlined the key differences between Letter of Map Amendments (LOMAs) and Letter of Map Revisions (LOMRs) - and why understanding these distinctions is vital for effective floodplain management. We aim to break down some of the barriers to implementing these map changes for our partners and the broader floodplain management community.

Letter of Map Amendments (LOMAs) and Letter of Map Revisions (LOMRs)

Full flood risk project studies and restudies occur at regular intervals. These involve changes to multiple Flood Insurance Rate Map (FIRM) panels and updates to associated Flood Insurance Studies (FIS). These efforts can take years. They involve public comment periods, and adoption by local communities. For communities that participate in the National Flood Insurance Program (NFIP), local adoption must be completed by ordinance. 

More limited flood map updates can occur outside of a full flood risk mapping project. These are collectively referred to as Letters of Map Change (LOMC).

There are two methods to change a special flood hazard area that has been officially mapped by the National Flood Insurance Program. The two methods are a Letter of Map Revision and a Letter of Map Amendment. These changes may be needed to acknowledge better topographic data, new modeling or physical changes that have taken place outside of an update to the overall risk map.

In all cases, a licensed land surveyor and/or registered professional engineer will need to be involved in the process. The Federal Emergency Management Agency provides forms that can be either filled out online or mailed. These are known as forms MT-EZ, MT-1, and MT-2. The required form varies by which type of change is requested. 

Letters of Map Revision (LOMR)

One way communities support FEMA is with accurate flood data. Whether initiated by a community, or an individual, Letters of Map Revision can assist with properly evaluating flood risk. There are two sub-types of Letters of Map Revision – the Letter of Map Revision based on Fill (LOMR-F) and Letter of Map Revision (LOMR). 


The LOMR-F is a process where an individual requests their property, or a portion of it, be removed from the mapped special flood hazard area based on fill material. Fill material cannot be placed in the regulatory floodway.

The LOMR-F process requires the Community Official make at least three findings. The Community Official must sign a document stating that the applicant will meet all local permitting requirements, including floodplain management requirements. The Community Official must also sign a document stating the applicant has separately met Endangered Species Act requirements. Additionally, the Community Official must state that the land and structures being removed from the special flood hazard area will be reasonably safe from flooding. 

Supporting data associated with the LOMR-F process must be kept by the Community Official and may be required to be submitted to FEMA. The LOMR-F process does not typically result in official map changes. 


The second type of Letter of Map Revision is the Letter of Map Revision – known as the LOMR. The process is used when physical changes, either natural or manmade, have occurred since adoption of the Flood Insurance Rate Maps (FIRMs). Examples of changes include development activity and stream meandering. Changes can also be prompted by updated technical studies or to correct known errors. Typically, these changes impact a single FIRM panel. These changes may impact the boundary of a Special Flood Hazard Area, the Base Flood Elevation, or the location of the Regulatory Floodway.

LOMR’s require the Community Acknowledgements previously described for LOMR-F’s. FEMA charges a fee associated with the cost of review. They also require notice and a comment period be provided to affected and adjacent communities and property owners. There is a 90 day appeal period on LOMR’s, and they become effective 6 months after issuance. 

A successful determination on a Letter of Map Revision will result in an updated Flood Insurance Rate Map, which are provided to the applicant and community, as well as published online on FEMA’s flood map service center. These updates may affect floodplain development and flood insurance requirements. LOMR’s need to be used in conjunction with the original FIRMs to provide a complete understanding of flood risk. 

Conditional Revisions – CLOMR-F and CLOMR

There is a conditional process for both the Letter of Map Revision based on Fill, and Letter of Map Revision. These are known as the CLOMR-F and CLOMR – where the “C” represents “conditional”. FEMA may comment on materials associated with a CLOMR-F or CLOMR as to how the project affects the hydrologic or hydraulic characteristics of a flooding source. A CLOMR-F or CLOMR will be issued provisionally where the physical changes have not yet occurred that will result in the requested revision. For example, a CLOMR-F will be issued when the fill material has not yet been placed. When the permitting and project are complete, FEMA will issue a LOMR-F.

A LOMR-F or LOMR must be submitted within 6 months of project completion to finalize the conditional process. 

Letter of Map Amendment (LOMA)

A Letter of Map Amendment (LOMA) is requested when a property owner disagrees with the mapping based on natural conditions of the property – in other words if the property has not been elevated by fill material. The review process includes an evaluation of the natural ground level of the area in question compared to the Base Flood Elevation. LOMAs are most frequently requested when a property is mapped within the SFHA, but there is an area that is naturally higher ground. 

The Letter of Map Amendment will be issued if it can be proven that the property or structure will not be inundated by the base flood. Letters of Map Amendment requests will result in a determination from FEMA. If approved, the letter will indicate the amended base flood elevation. Letters of Map Amendment do not result in changes to the published mapping. Property owners and communities are notified of the decision on LOMA requests. Approval may result change whether or not flood insurance is required. 

A LOMA-OAS (out as shown) is an official determination issued by FEMA that states a property was already outside the SFHA. This process is frequently used when a property or structure is near the SFHA boundary and official determination is needed for development permitting or insurance requirements. This does not change the map, only clarifies the existing map. 

A LOMA-DEN (Denial) will be issued if FEMA determines the ground elevation is below the BFE. Community officials and others evaluating flood risk should be careful to note the “DEN” designation that officially denies the LOMA request.

How Forerunner can help

Forerunner is used by communities across the country to navigate flood map changes and enable staff to communicate those changes to the public.  The dashboard consolidates datasets and maps for floodplain management, disaster recovery, and resilience planning in one place. 

The platform seamlessly integrates your latest mapping data by pulling FIRMs directly from FEMA's National Flood Hazard Layer (NFHL). It can also accommodate historic and non-FIRM regulatory maps, pulling data from both private and public sources, so that your teams can add in all relevant map layers. The data automatically updates as well, enabling you to make decisions based on the most up-to-date information. 

Once your community effectively implements map changes, communication is key. Forerunner’s internal and public dashboards empowers agencies to:

  • Compare Preliminary and Effective FIRMs. Your team, property owners, local insurance agents, developers and other stakeholders can compare changes that may occur to the flood risks in the area.
  • Automatically surface changes on impacted properties. Forerunner’s automated warnings will flag every property that may experience a zone or BFE change so your team and the public can easily understand if a property is impacted by upcoming changes. 
  • Easily generate letters for public outreach. Forerunner’s letter generation tool makes it easy to share flood zones, BFEs and other property data for property in a formal letter.

If you are interested in learning more about Forerunner, we’d love to connect! Please reach out or request a demo.

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