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DNR officials brief Koochiching County on 2022 floodplain mapping and next steps
Summary
State floodplain staff explained why FEMA maps changed, described inputs such as LiDAR and USGS gauges, and offered to study areas of local concern including the Little Fork and Rainy rivers.
INTERNATIONAL FALLS, Minn. — Officials from the Minnesota Department of Natural Resources and FEMA contractors presented updated floodplain mapping methods to the Koochiching County Board of Commissioners on March 25 and discussed next steps for addressing areas where the 2022 maps changed boundaries relative to older maps.
State floodplain manager Celia Strauss and floodplain engineer Jeff Weese reviewed how modern mapping uses LiDAR topography, repeated cross‑section modeling, and long‑term USGS streamflow records to delineate the 100‑year floodplain. They said those updated inputs explain why some floodplain boundaries grew between the county’s older maps (1996 and earlier) and the 2022 revisions.
Board concerns and DNR response
Commissioners and county staff raised concerns that the revised maps had placed some parcels into the mapped floodplain that previously were considered outside it. Officials discussed factors that can affect mapped elevations, including historical ice and debris jams at bridges, which are not explicitly modeled in standard hydraulic analyses. DNR staff said ice jams and debris events are difficult to quantify for models and are not typically included in FEMA hydraulic inputs; the state added that local high‑water marks and dated photographs can help “ground‑truth” models.
DNR offered to pursue additional technical reviews of specific streams. County staff and commissioners requested that DNR and its contractors examine the Little Fork River, Big Fork River and the Rainy River for potential refinements. DNR said it already has a Rainy River technical effort under contract with FEMA and that available budget would determine how much additional work could be done in Koochiching County.
National Flood Insurance Program implications
DNR staff reviewed the practical implications of the county’s participation in the National Flood Insurance Program (NFIP). Participation requires a local ordinance and permits to regulate development in mapped floodplains, and makes federally backed mortgage holders eligible for flood insurance. DNR staff said communities not participating in NFIP would limit residents’ options for standard flood insurance and could affect eligibility for some federal public‑assistance reimbursements following major disasters.
How residents can help
County staff asked residents who have dated photos or known high‑water marks from past floods to provide that documentation; DNR said such records, combined with USGS gauge flows, can be used to re‑examine model inputs and help the agency determine whether a letter of map revision or other technical revision is warranted.
What’s next
DNR and county staff agreed to stay in contact. DNR will continue the Rainy River work already under way and evaluate whether available contract budget can be used to study specified Koochiching streams. Commissioners asked county staff to collect dated photographic and survey evidence from residents to support any review requests.
