Why Retention Alone Is Not Enough

Retention, or distributed storage, will not eliminate the need for the upstream staging component of the Fargo-Moorhead (FM) Area Diversion Project.

The implementation of distributed, upstream storage could have the potential to reduce the frequency of diversion channel operation, thereby reducing how often the upstream staging area will be utilized.  In addition, distributed, upstream storage could help reduce the duration of the staging area during certain flood events.  However, the staging area immediately upstream of the Fargo-Moorhead area is still necessary to offset the downstream impacts of the project for a variety of flood events, and is located in the most reliable, effective and efficient location.

The Red River Basin Commission (RRBC) has set a long-term goal of a 20% flowage reduction in the Red River.  To achieve that goal, the RRBC’s recent Halstad, MN Upstream Retention (HUR) study identified 97 sites that would require approximately 108,000 acres, 169 square miles, or 4.7 townships of land for distributed, upstream retention.  Keep in mind that based on past projects, it takes years of study and development just to get one detention site permitted, let alone acquire the land and construct the project.

Assuming an industry standard of $2,000/acre-foot for 580,000 acre feet of retention on these 97 potential sites, the estimated cost would be $1.16 billion.  The staging area, which is an essential part of the Diversion Project, provides approximately 150,000 acre-feet of retention on 32,500 acres.

These results suggest that the staging area included in the Diversion Project is the most effective and efficient retention for mitigating the downstream impacts.  The proposed staging area will cost less and impact fewer acres of land than distributed upstream retention, and it will concentrate impacts in Cass and Clay Counties.

The Diversion Authority has pledged $25 million to upstream retention projects. The funding is for projects that demonstrate benefit to the Fargo-Moorhead area.

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