Mitigating Historic Flood Issues

In Pennington County, Ditch (CD 70) has been a source of agricultural and urban flooding problems for years. Since its construction a century ago, the ditch has routinely flooded out of its banks despite cleanouts and culvert replacements. It has decimated crops, placed businesses in a precarious position and challenged the Red Lake Watershed District and City of Thief River Falls. It provided just a two-year level of protection in agricultural areas and 10-year level of service in residential and commercial areas. This means a minor rainstorm — just 3 inches — could cause flooding in rural areas while anything more could create safety hazards, damage property or become a public nuisance.

The $7 million Thief River Falls Flood Damage Reduction project mitigates the historic flooding concern by improving drainage within the system, plans for future development, and provides 100-year protection in urban areas and 10-year service for agricultural areas. The project team overcame challenging existing conditions and coordinated with ongoing infrastructure and roadway improvements. The project uses a diversion channel with vegetated buffers, storm sewers, culverts, side water inlets, and a granite rock chute to improve flood protection and drainage for future development, dissipate energy from peak flows, enhance water quality, and reduce the impacts of scour and erosion.

One of the project’s remarkable aspects was multiple entities working together. The team coordinated with several partners throughout the project, including the Red River Watershed Management Board, State of Minnesota Damage Reduction Program, Red Lake Watershed District, City of Thief River Falls, Pennington County, Minnesota Department of Transportation, several benefitting landowners and local citizens and businesses. The Red Lake Watershed District, Pennington County, City of Thief River Falls, MnDOT and the Red River Watershed Management Board collaboratively combined three public works projects involving a new bridge, a trunk highway urbanization corridor, and the flood damage reduction project totaling over $20 million in construction costs. The team worked alongside the public, held meetings and open houses, and overcame significant design challenges and utility conflicts. This included electric, telephone, fiber optic, natural gas, water, storm sewer and the city’s primary sanitary sewer conveyance system. 

Completed on schedule and on budget, the new Westside Flood Damage Reduction Project provides protection for future development and reduces flood potential, property damage and crop losses.