Lower Yellowstone Dawson Fallon & Powder River Counties
Dawson, Fallon, and Powder River Counties are working with MT DNRC and FEMA to update and produce new Flood Insurance Rate Maps (FIRMS) for the Yellowstone River and Tributaries through Dawson County, Sandstone Creek and tributaries through Fallon County, and the Powder River and Little Powder River through Powder River County. Updated floodplain maps will depict the latest, most accurate flood risk data, and will eventually replace the existing floodplain maps.
DNRC held project kick off meetings with all the communities September 19 & 20, 2022.
History of floodplain maps in County and City:
Flood Hazard Boundary Maps (FHBMs) were originally produced in 1974 for the city of Glendive and in 1978 for Dawson County. Glendive is the only incorporated community within the county. In 1981, a Flood Insurance Study (FIS) and FIRMs were produced for Glendive. Dawson County was not a part of that study. Dawson County’s FHBMs were converted to FIRMs by letter in 1999. Within the county, all of the existing mapping is approximate, based on the original FHBMs and other limited data from the late 1970’s. There have been no mapping updates to the maps since 1981.
2022 Flood Study:
This project will conduct new floodplain mapping studies on 55.8 miles of the Yellowstone River within Dawson County, 82.2 miles of tributaries, 15 ponds and reservoirs, 205 miles of base level engineering (approximate A study), modernizing the existing paper inventory in Dawson County. The overall project covers 370.6 miles of updated floodplain mapping. Including new field survey, base map preparation, hydrologic and hydraulic analyses, and floodplain mapping for the county and city.
Estimated project timeline:
History of floodplain maps:
Flood Hazard Boundary Maps (FHBMs) were originally produced in 1975 for the City of Baker. Flood study work completed by the SCS in 1985 was incorporated into FIRMs issued to the city and county in 1988. There have been some revisions to the maps over the years, including two LOMRs (2013 and 2018) that were completed in the county and part of the city. No other revisions or updates have occurred to the FIRMs since 1988.
2022 Flood Study:
This project will conduct new floodplain mapping studies on 15.1 miles of enhanced with floodway tributaries, 10.9 of those miles are on Sandstone Creek. New floodplain mapping studies will also be done on 2.7 miles of enhanced tributaries along with 5.1 shoreline miles. The overall project covers 17.8 miles of updated floodplain mapping. Including all new field survey, base map preparation, hydrologic and hydraulic analyses, and floodplain mapping for the county and city.
Estimated project timeline:
History of Floodplain maps:
Flood Hazard Boundary Maps (FHBMs) were originally produced in 1979 for the Powder River County. A FHBM was originally produced for the Town of Broadus in 1974 and revised in 1978. All of the mapping was approximate A mapping. The county and town FHBM maps were converted by letter into the regular program of the NFIP in 2010. In 2014, a LOMR was completed for approximately four miles of the Powder River through town limits and included a small part of the county. The LOMR provided the town and county with newer information and BFEs, however, the mapping revision was still in paper format, remaining a challenge for local administration. No other revisions have occurred to the effective mapping.
2022 Flood Study:
This project will conduct new floodplain mapping studies on 29.7 miles of the Powder River, 20.2 miles of the Little Powder River, 19.5 miles of BLE, modernizing the existing paper. The overall project covers 69.4 miles of updated floodplain mapping. Including all new field survey, base map preparation, hydrologic and hydraulic analyses, and floodplain mapping for the county.
Estimated Project Timeline:
