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Army Corps of EngineersThe Corps of Engineers recently sent individual letters to members of the Richland Wilkin JPA which included clarifying information on potential impacts when the Fargo-Moorhead Area Diversion Project is in operation. The letters also included information on storage and the proposed improvements to the project.

The information in the letters support the belief that the proposed Diversion Project and areas of impact are the best flood risk reduction solution for the Fargo-Moorhead metropolitan area.

Information on all of the entities, including links to the letters and maps, have been posted in the Library section of FMDiversion.com.

Summary of Impacts

  1. 18 of the 32 members would have no direct impact from the project.
  2. 96 percent of the Staging Area is located in Cass and Clay counties, the counties that primarily benefit from the Project.
  3. Richland County and associated townships and cities:
    • Only 3 residential structures and 1071 acres would be impacted during a 100-year event that would not already be impacted under existing conditions.
    • A vast majority of additional-depth impacts to structures and acres are between 0 and 1 foot.
    • The additional duration of flooding at elevations of concern is estimated to be 2 to 3 days.
    • There would be no impacts during a 10-year event.
  4. Wilkin County and associated townships and cities:
    • Only 2 residential structures and 995 acres would be impacted during a 100-year event that would not already be impacted under existing conditions.
    • A vast majority of additional-depth impacts to structures and acres are between 0 and 1 foot.
    • The additional duration of flooding at elevations of concern is estimated to be 2 to 3 days.
    • There would be no impacts during a 10-year event.
  5. Pleasant Township, Cass County, ND:During operation of the Diversion under a 100 year event, a maximum of 6,241 acres would be impacted by the project that wouldn’t be under existing conditions. The additional depth caused by the project is estimated to range between 0 and 8 feet.
  6. Holy Cross Township, Clay County, MN:During operation of the Diversion under a 100 year event, a maximum of 9,814 acres would be impacted by the project that wouldn’t be under existing conditions. The additional depth caused by the project is estimated to range between 0 and 8 feet.
  7. All Entities:The Project would not operate until a 10-year event, virtually eliminating the likelihood of flood water staging in the summer and causing crop damage.

Storage

We understand that the storage component of the proposed Diversion Project is of concern to the JPA. The Staging Area provides approximately 215,000 acre-feet of effective storage located immediately upstream of the diversion. During a 1-percent-chance (100 year) flood event, this storage would affect approximately 32,500 acres, of which approximately 18,300 acres (56 percent) are located in Cass County and 13,000 acres (40 percent) are located in Clay County, the counties that primarily benefit from the Project. In comparison, the storage would affect fewer than 800 acres (2.5 percent) in Richland County and 450 acres (1.5 percent) in Wilkin County.

In addition, the Corps and the Diversion Authority have considered other flood storage options. Local Water Resource Districts have completed a sensitivity analysis for the 2009 flood event on the Wild Rice River which demonstrates that distributed storage is not a viable option to replace the storage component of the Project. If distributed storage was pursued for the Wild Rice River, nearly all of the storage would need to be placed in eastern Richland County, impacting much more land in the county than the Staging Area. Additionally, even if this occurred, the distributed storage would not be enough to replace the storage required for the diversion channel. Similar results can be expected for the other tributaries and Wilkin County. The volume of retention needed farther upstream in the Red River watershed to mitigate downstream impacts would be significantly higher than the 215,000 acre-feet included in the upstream staging area. It would directly impact more land, cost more, and would transfer impacts to counties that would not benefit from the Diversion Project.

In summary, the proposed project and areas of impact are believed to be the best solution for the Fargo-Moorhead metropolitan area, yet it is recognized that distributed storage could reduce the frequency of project operation. The Red River Basin Commission and other agencies are continually investigating water storage and retention solutions for the entire Red River Basin, and the Diversion Authority has pledged $25 million to advance retention that benefits the Fargo-Moorhead metropolitan area.

Project Improvements

The Corps and Diversion Authority are proposing to move the channel alignment north, add gates to the diversion inlet, and add levees within the communities of Fargo and Moorhead. The Corps is performing an environmental review of the proposed changes before determining whether to formally include them in the Project. These changes would reduce the direct impacts to residential structures (reduce from 387 to 58), maintain the ability to farm within the Staging Area, and preserve the tax base of those impacted areas. The Corps and Diversion Authority will continue to seek out opportunities to minimize impacts as part of this Project. However, it is important to point out that any project will have impacts and the upstream storage is a critical component of the Project.

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