- Floodproofing and Retrofitting - Guidelines for design.
- FEMA Elevation Certificates - Required to document surveyed elevations and is used for most map appeals to FEMA (LOMCs). It is used by many communities for as-built documentation.
- Elevation Certificates: Who Needs Them and Why
- Minnesota Sample "No-Rise" Certificate
- NAVD88 to NGVD29 Conservation Map for Minnesota - FEMA has historically used the NGVD29 datum for referencing flood elevations and has since switched to NAVD88. It is very important to know what vertical datum your referencing and using.
Bridge and/or Culvert Floodplain Requirements
Letters of Map Revisions
A Letter of Map Revision (LOMR) is a letter from FEMA officially revising the Flood Insurance Rate Map (FIRM) or Flood Insurance Study (FIS) to show changes to floodplains, floodways, or flood elevations.
LOMRs are often completed when there is a proposed project that changes the circumstances in a watershed or stream. A CLOMR is used to show that a proposed project would be eligible for a LOMR (or physical map revision) once the project is constructed.
Examples of projects that may require a LOMR:
- Projects that affect or change watershed hydrology - such as a dam, diversion channel, or detention basin
- Projects that affect or change stream hydraulics - such as channelization, new bridges or culverts, or levees
- Projects that change topographic conditions in the floodway - such as grading or filling
- Projects that change the floodway boundary such as stream realignment
LOMRs may be completed if there are errors in the effective FIRM or FIS or if there is better available data that can be incorporated into the FIRM or FIS, but they are not required.
Changes in watershed hydrology require an additional review by the Interagency Hydrology Review Committee (IAHRC) in addition to the LOMR or CLOMR review by FEMA and the MnDNR. If a proposed project will change watershed hydrology for a FEMA modeled and mapped stream, contact the DNR for guidance on submitting information to the IAHRC.