BLE and Letters of Map Revisions (LOMRs)

Once Flood Insurance Rate Maps (FIRMs) are released as effective the flood hazard information (floodplain extents,

floodways and Base Flood Elevations) should be maintained by the

community and local developers who modify the natural drainage areas with

grading and construction activities. The Code of Federal Regulations was

updated in the 1980s and 1990s to formalize the submittal requirements

and share the maintenance requirements of the FIRM to include the

development community and locals. The intent was to move the cost of

maintenance from all taxpayers to those that “benefit from the modification”.

The minimum requirements for communities participating in the National

Flood Insurance Program (NFIP) all proposed development activity should be

permitted. Additionally, local reviews should be completed to assure that,

the project, once completed will be reasonably safe from flooding. This is

completed through local permitting and local floodplain management reviews. Local permitting that results in

modifications to the flood information on the FIRM should be submitted within six-months after construction has been

completed. 44 CFR 65.3

Zone AE areas (no floodway).

When a floodway has not been designated, communities are responsible for

monitoring all proposed development to assure that the cumulative effect of the planned modifications to be made

during construction (in combination with all existing and anticipated development) will not increase the base flood

elevation (BFE) more than one foot at any point along the study area. 44 CFR 60.3(c)(10)

In the case where a proposed project increases the BFE more than

1.0 foot, a Conditional Letter of Map Revision (CLOMR) is required.

Zone AE areas (with floodway). When a floodway is shown on the

FIRM in the vicinity of a proposed development, the community is required to

prohibit encroachments (fill, new construction, or other improvements)

unless it has been demonstrated through analysis that the proposed

development would

not result in any increase in the base flood elevation in

the vicinity of the proposed project. 44 CFR 60.3(d)(3)

In the case where a proposed project increases the BFE more than

0.0 foot, a Conditional Letter of Map Revision (CLOMR) is required.

Flood Insurance Rate Maps

(FIRMs) are based upon existing

conditions at the time of the

analysis.

LOMRs review the as-built (post

construction) ground conditions

against the current effective

FIRM information.

BLE and Letters of Map Revision (LOMRs)

REQUIRED WHEN: Changes to physical/climatic information results in a change to the

flood hazard information in the vicinity of flooding sources shown

on FIRMs. Man-made changes (grading or moving flood source)

and culvert/bridge addition or replacement

PURPOSE: Change effective flood delineations/extents, floodway and/or Base

Flood Elevations (BFEs)

RESULT: FEMA issues a letter/document, as well as revised Flood Insurance

Rate Map (FIRM)/Flood Insurance Study (FIS) documents.

LOMR

Letter of Map Revision

Conditional LOMRs review

projects prior to construction

activities taking place.

CLOMRs review the difference

between the pre-project and

proposed (post-project)

conditions. This is done to

isolate the flood level changes

due to the proposed project.

Zone A areas. When a floodplain has been provided on the FIRMs, but does not show any Base Flood Elevations,

it is designated a Zone A (or Zone A1-A30). These areas still require coordination with local development authorities

and should provide a pre-project and proposed project analysis to assist local community officials in understanding

the project’s effects prior to permitting or construction. A CLOMR submission may be requested if the project is found

to increase the base flood elevations more than 1.0 foot at any point in the vicinity of the proposed project.

BLE as Available Flood Hazard Information. Both LOMRs and CLOMRs require engineering modeling to

be prepared for comparison. Base Level Engineering (BLE) makes skeleton models available for use and may be

used to prepare LOMR and CLOMR submittals. The table below indicates how BLE may be used to prepare required

submittals for local permitting reviews in the vicinity of flood prone areas.

Project Changes Flood Zone on FIRM Can BLE be used?

Man made changes

have been completed

For a full list of

development

activities reference

44 CFR 59.1 –

Definitions.

H&H analysis and floodplain

mapping for completed project

indicates changes to the

floodplain, floodway and/or

base flood elevations in the

study reach

ACTION:

Submit LOMR to update FIRM

Post-Project Model

1. No Effective Flood

Data, no flood zone

2. Zone A

3. Zone AE (with or

without floodway)

1. Yes, use for pre- and post-

project conditions

2. Yes, use for pre- and post-

project conditions

3. No. BLE terrain input may be

used to update cross-section

data in pre-project conditions

or provide data upstream and

downstream of project area.

Proposed man-made

development activity

H&H analysis is to be provided

for the following two

conditions:

• Pre-Project

• Proposed Project

Review graphic above to

identify when CLOMRs are

necessary.

ACTION:

Submit Conditional LOMR

(CLOMR) to determine project

effects.

Pre-Project Model

1. No Effective Flood

Data, no flood zone

2. Zone A

3. Zone AE (with or

without floodway)

Proposed (Post-Project)

4. Any Zone

1. Yes, model may be used as is

for existing conditions.

2. Yes, model may be used as is

for existing conditions.

3. Yes, model may be used,

however will likely require

refinement*

4. No. Proposed ground

conditions

*Refinement may include updated topography (breaklines, cell density), integrating existing structure information from effective

modeling or updates to hydrologic or hydraulic model inputs.

REQUIRED: When a project’s effects are found to be larger than 0.0 ft in

Zone AE (with floodway) or 1.0 foot in Zone AE (no floodway), the

project should be reviewed locally for mitigation measures and

should be required to submit a CLOMR to FEMA.

PURPOSE: Review of pre-project versus post-project conditions. Provides an

awareness to surrounding property owners and requires contact to

alert them of potential effects to their property prior to construction.

RESULT: FEMA issues a letter to indicate the potential changes to the

floodplain, floodway and Base Flood Elevations relative to the

proposed project.

CLOMR

Conditional

Letter of Map Revision

Additional Resources. The Code of Federal Regulations, NFIP minimum floodplain requirements, and FEMA

submittal processes are very complex and initiate a high volume of calls and inquiries to FEMA’s Mapping and

Insurance eXchange (FMIX). The following resources can provide additional information for communities, property

owners and the development industry.

• Protecting Floodplain Resources – A Guidebook for Communities

(www.hsdl.org/?abstract&did=456496)

• Reducing Losses in High Risk Flood Hazard Areas

https://go.usa.gov/xsGwX

• Managing Floodplain Development Through the NFIP, Unit 5 (NFIP Requirements)

https://go.usa.gov/xsGwU

• Tutorial Flood Insurance Rate Maps (https://go.usa.gov/xsGw7)

• MT-2 Forms and Instructions (https://go.usa.gov/xsGwM)

• On-Line Letter of Map Change (https://go.usa.gov/xsGfa)

• Tutorial – On-Line LOMC Tools (https://go.usa.gov/xsGfr)

Contact the FEMA’s Mapping and Insurance eXchange (FMIX) by phone at 1-877-FEMA-MAP (336-2726)

between 9:00am and 5:00pm (eastern) or via email at [email protected].

• Local community reviews are used to assure that development meets both minimum federal and

higher-local floodplain requirements.

• The authority to approve/deny development exists at the local level. Permits are issued by

communities.

• FEMA’s LOMR and CLOMR reviews are intended to assure that FEMA has the required

documentation to update the Flood Insurance Rate Maps (FIRMs) with new information.

• FEMA does not approve development for participating NFIP communities.

• A LOMR allows FEMA to revise flood hazard information on an NFIP map via letter without

physically revising and reprinting the entire map panel.

• The requester is responsible for providing all the information needed for the review, including (if

necessary) elevation information certified by a licensed land surveyor or registered professional

engineer.

• According to FEMA’s Technical Bulletin 10-01 “to be reasonably safe from flooding during the

Base Flood condition, the basement must (1) be dry, not have any water in it, and (2) be

structurally sound, not have loads that either exceed the structural capacity of walls or floors or

cause unacceptable deflections.”

• FEMA does charge a review fee for LOMRs and CLOMRs. Review the current fee schedule at:

https://go.usa.gov/xsGwr.

QUICK FACTS

Check Effective FIRM

Document flood zone

(or lack of one)

Check Base Level

Engineering data

Is data available, if

so, download for

potential use

Can BLE be used?

If yes, use as

outlined on

If no,

use effective

Submit M2 Forms

Use paper or

online submission

process

Integrate Base Level Engineering when possible in agreement with the workflow below. Leverage available

engineering models to prepare submittal requirements. A high-level workflow is identified below for reference: