FLOOD PLAN REVISIONS FOR TITTABAWASSEE BETWEEN EDENVILLE and sanford and Conditional Letter of Map Revision (CLOMR)

A Notice of Conditional Letter of Map Revision (CLOMR) will be provide in the coming weeks, as a requirement by the State and FEMA for the permitting of the Edenville Dam. Once the Notice is approved by FEMA we will publish it.

​What is a Conditional Letter of Map Revision (CLOMR?)

​A Conditional Letter of Map Revision (CLOMR) is a letter from the Federal Emergency Management Agency (FEMA) providing formal comment if a proposed project will meet the minimum requirements of the National Flood Insurance Program (NFIP). In this case, FEMA is reviewing the proposed flood hazard changes to the Special Flood Hazard Area (SFHA) and Base Flood Elevations (BFEs) extending from the Edenville Dam to the Sanford Dam related to the proposed design and reconstruction of the Edenville Dam. CLOMRs are part of a process developed by FEMA to ensure the published flood hazard information used for flood insurance is kept updated.

​What is a Special Flood Hazard Area (SFHA) and Base Flood Elevation (BFE)?

​The SFHA depicts the flood hazard area related to the 1% statistical probability of being exceeded in any given year and is also referred to as the 1% annual-chance flood, the 100-year flood, and the base flood. SFHAs are labeled as Zone A, Zone AO, Zone AH, Zones A1-A30, Zone AE, Zone A99, Zone AR, Zone AR/AE, Zone AR/AO, Zone AR/A1-A30, Zone AR/A, Zone V, Zone VE, and Zones V1-V30 on the Flood Insurance Rate Map (FIRM). The SFHA is used to determine flood insurance requirements for properties in communities participating in the National Flood Insurance Program (NFIP). A BFE is the flood elevation of the SFHA at a given location.

​Why is a CLOMR being requested?

​CLOMRs are required where proposed projects may increase BFEs by more than 1.0 foot where the SFHA is determined using detailed hydraulic methods. The SFHA between Edenville Dam and Sanford Dam is currently designated as “Zone AE,” meaning a detailed hydraulic analysis was completed. A CLOMR is required as a condition of permitting by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) for the Edenville Dam reconstruction project. A CLOMR was not required as a condition of permitting for the reconstruction of the Sanford Dam because the new hydraulic analysis predicts BFEs to decrease as a result of the proposed project. CLOMRs were not required as a condition of permitting for reconstruction of the Secord Dam and the Smallwood Dam because the SFHA is designated as “Zone A” and is based on an approximate hydraulic analysis. Changes to the SFHA are expected along the Tittabawassee River from Secord Dam to Sanford Dam. After reconstruction of all four dams is complete, FEMA will review the SFHA by application of a Letter of Map Revision (LOMR). A LOMR is a letter from FEMA officially revising the SFHA on the FIRM. Changes to the SFHA will not be formally adopted until FEMA issues the LOMR after the reconstruction projects are complete.

​What is the area of proposed floodplain boundary changes related to the
​CLOMR?

​The proposed changes to the SFHA and BFEs include the floodplain area along the Tobacco River from the Edenville Dam to the Tittabawassee River, and the Tittabawassee River between the Edenville Dam and the Sanford Dam including Sanford Lake.

​Why is the floodplain boundary proposed to change?

After the failure of the Edenville Dam in 2020, a new detailed hydraulic analysis has been completed to compare the flood elevations from the pre-failure dam geometry to the proposed dam geometry. The new analysis predicts there may be locations where the BFE increases and decreases, and the SFHA widens and narrows, compared to the Zone AE SFHA boundary and BFE information published on the existing FIRM which became effective in 2013. These changes are a result of new hydraulic methods, proposed project geometry, and better topographic information.

​How does this relate to other flood studies being done downstream of
​Sanford Dam?

Midland County and the Midland Business Alliance (MBA) are currently conducting additional flood studies of the Tittabawassee River and its tributaries with the United States Army Corps of Engineers (USACE). These studies include a detailed flood response study of the Tittabawassee River system and proposed flood reduction projects. These studies are not related to FEMA’s National Flood Insurance Program. Four Lakes Task Force is collaborating with the USACE and the MBA with the hydrologic studies completed for the reconstruction of the Secord, Smallwood, Edenville, and Sanford dams. 

​Will this affect flood insurance requirements for my property?

Changes to the SFHA between the Edenville Dam and the Sanford Dam are only proposed and are not being modified at this time. Formal adoption of changes to the SFHA will not occur until after reconstruction work is complete, and FEMA issues a LOMR to officially modify the SFHA.

​For specific questions on how this may affect your flood insurance premium, contact your insurance agent.

For more information regarding the National Flood Insurance Program (NFIP), visit FEMA’s website or the NFIP Frequently Asked Questions page on EGLE’s website.
 
For more information regarding the Edenville Dam reconstruction, contact Four Lakes Task Force at [email protected].

View the FEMA Floodplain Topographical Maps,