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General questions regarding the Fargo-Moorhead (FM) Area Diversion Project
Other FAQ Sections:
Oxbow/Hickson/Bakke Ring Levee Option FAQ Answers to questions about the Ring Levee Option for the Oxbow, Hickson and Bakke area.
Low Flow Channel FAQ Answers to questions about this feature of the Diversion Project.
Land Acquisition FAQ Answers to questions specific to land acquisition and associated topics.
Answers to Questions from the Public Answers to questions posed by the public in the Comments section about the Diversion Project
A three-year study led by the Corps of Engineers, and also involving local engineering firms, found that a diversion was the only concept that could significantly reduce flood risk in the Fargo, ND-Moorhead, MN area from flood events larger than the 2009 event. A diversion channel is the safest and most robust flood risk reduction option available because no matter the size of the flood, a diversion channel will provide some benefits.
When floods exceed the capacity of levees and dams, the results can be catastrophic. A number of alternatives, including levees and water retention, were analyzed before a diversion channel was recommended.
The Fargo area lacks high ground to begin and end levees, and that limits the potential levee height. As such, the largest cost-effective levee plan could only be certified up to the 2-percent chance event. This left an intolerable level of remaining risk, so the levee alternative was dropped from consideration as a stand-alone alternative.
For greater levels of protection, a ring levee would have to be built around the cities of Fargo and West Fargo, ND, making this option cost prohibitive.
Flood storage was also considered. Water resource managers in the Red River Basin estimated in the Fargo-Moorhead and Upstream Feasibility Study that up to a total of 400,000 acre-feet of flood storage (or 40,000 acres covered with 10 feet of water) could be constructed at various locations upstream of Fargo-Moorhead at a cost of approximately $600 million. Such a system of storage sites would reduce the 100-year flood crest at Fargo by less than two feet. The proposed diversion would reduce the 100-year flood stage in Fargo by 12.4 feet.
The local sponsors for the project, the cities of Fargo and Moorhead, as well as representatives from Cass and Clay counties, overwhelmingly supported the North Dakota diversion and selected it as their Locally Preferred Plan because it reduces flood risk for a much larger portion of the metro area.
The current alignment was selected for technical and policy reasons. The design intent was to benefit as much existing development as possible, while minimizing overall impacts to the floodplain and the environment, while at the same time, minimizing costs.
The diversion alignment was located to keep flood water out of the Rose Creek watershed by capturing overland flows south of Fargo and to stay south and west of the existing Sheyenne River Diversion control structure at Horace, ND. The diversion outlet was located downstream of the mouth of the Sheyenne River to maintain natural drainage within the benefitted area. The channel alignment north and west of Harwood, N.D. was adjusted to avoid Drain 13, as requested in a petition from local landowners. In general, to the extent possible, the alignment avoids existing structures and crosses rivers and roads at right angles.
The diversion project will significantly reduce flood damages in the benefitted area by reducing the frequency of high flows in the natural river channels through town. For floods up to a 100-year event, only minimal emergency efforts would be required within the benefitted area. A 500-year flood would cause a stage of approximately 40 feet with the diversion channel in place that would require emergency measures similar to those used during the 2009 flood (stage of 40.8 feet). It is important to remember that the Fargo-Moorhead area is prone to localized flooding from extreme rainfall events, and the diversion project would not reduce that risk.
At the Wild Rice River, there will be a gated water control structure similar to the one on the Red River at the upstream end of the project. Where the diversion crosses under the Sheyenne and Maple rivers, aqueduct structures will allow some of the natural river flows to cross over the diversion. Similar structures are more common in Europe and have been constructed in the United States, typically for water supply or canal projects. The Rush and Lower Rush rivers will be completely diverted into the diversion channel via drop structures. The existing Rush and Lower Rush river channels will be abandoned.
In the May 2010 Draft EIS, the tentatively selected plan had an estimated first cost of $1.3 billion. In early fall of 2010, the Corps refined the Draft EIS with the new data the Corps collected during the study process. The new data indicated that the diversion channel had to be adjusted to minimize the contact with the Brenna clay formation (a weaker soil). These adjustments to the plan increased the first costs to $1.5 billion. Shortly thereafter, the Corps determined that the downstream impacts from the North Dakota 35K diversion were not acceptable. The Corps modified the plan to include upstream impacts in an effort to minimize the extensive downstream impacts, and the mitigation for the upstream impacts increased the first costs to $1.7 billion.
The non-federal sponsors must enter into a Project Partnership Agreement with the Corps of Engineers to construct the Project. This agreement sets the required cost sharing of the Project between the non-federal sponsors and the federal government and requires that the non-federal sponsors be solely responsible for the Operation and Maintenance of the Project. The sponsors are responsible for financing their local share and operation and maintenance costs. It is currently anticipated that the non-federal sponsors will be the cities of Fargo and Moorhead. Mitigation required during project construction will be cost-shared. Mitigation required after the project is constructed and being operated and maintained by the non-federal sponsors will be the responsibility of the non-federal sponsors.
The federal portion of the project will be funded annually through the federal appropriations process. The non-federal sponsors will be responsible for generating the funds necessary to pay the non-federal share of project costs. The non-federal sponsors have completed the necessary financial self-certifications to complete the feasibility report and enter into a Design Agreement. These certifications indicate that they are financially capable of moving forward with the selected plan. Additional financial certifications will be necessary prior to beginning construction.
The project purpose, as stated by the Corps of Engineers in its reports, is “to reduce flood risk, flood damages and flood protection costs related to the flooding in the Fargo-Moorhead Metropolitan Area.” The staging area is not a permanent pool and therefore is not a water supply reservoir. Only for the most severe flood events will there be an effect from additional depth and duration. Even with a 1-percent chance spring flood event, the duration of standing water is estimated to only increase 5 to 15 days.
The hydraulic model developed in the feasibility study extends from Abercrombie, North Dakota to Emerson, Manitoba.
Local drainage issues along the entire diversion channel will be addressed in detail during the design and implementation phase. The project will be designed to minimize impacts to tributaries, especially for smaller, more frequent flood events. The design goal is to not change the one-percent chance floodplain outside of the diversion. The project will include measures to capture and direct flows along the Highway 17 tieback levee into the diversion channel. Future design details will be shared with the public once available. The Locally Preferred Plan is not expected to increase flood stages anywhere on the Sheyenne, Maple, Rush, and Lower Rush Rivers.
Recreation features are generally included in flood risk management projects because they provide additional economic benefits to the local communities at relatively small cost. Flood risk management projects in Grand Forks, ND; and St. Paul, Rochester, and East Grand Forks, MN; included such features. The cost of recreation features are shared 50/50 between the non-federal sponsors and the federal government.
Recreation features are generally included in flood risk management projects because they provide additional economic benefits to the local communities at relatively small cost. The staging area is not a permanent pool, and as such, is not part of the recreation plan for the project. Only for the most severe flood events will there be an effect from additional depth and duration. Even with a 1-percent chance spring flood event, the duration of standing water is estimated to only increase 5 to 15 days.
The level of risk reduction targeted in this project was guided by a goal set by the non-federal sponsors’ Work Group. The Metro Flood Study Work Group (MFSWG) established the goal of a stage of 36 feet at the Fargo gage during a 0.2-percent chance event, or the 500-year event. The project does not meet that original goal; however the MFSWG has accepted the level of flood risk reduction provided by the selected diversion project, which is a stage of 40 feet for the 0.2-precent chance event. The proposed diversion would not remove the entire metropolitan area from the 0.2-percent chance floodplain, but it would enable Fargo and Moorhead to pass a 0.2-percent chance event with emergency floodfighting similar to the efforts conducted during the 2009 flood. See section 7.4 of Appendix O of the SDEIS for more details.
Hydraulic modeling showed that the downstream impacts were far greater than first anticipated, extending beyond Drayton, ND, approximately 211 river miles downstream, and probably into Canada. Further study showed that the downstream impacts could almost entirely be eliminated by temporarily staging approximately 200,000 acre-feet of water immediately upstream of the diversion. Staging water upstream would affect approximately 1,000 structures as compared to approximately 4,500 structures affected downstream without staging. The recommended plan, the LPP with upstream staging and storage, impacts less people and less property and the impacts do rise to a level where mitigation can be performed. The alternative that allowed downstream impacts affected more people and more property, while the LPP with upstream staging and storage impacts fewer people over a smaller area.
The plan includes staging and storage upstream of the diversion channel inlet to nearly eliminate downstream impacts. Modeling indicated that we would need to store approximately 200,000 to 400,000 acre feet of water to reduce the one-percent chance flood crest at Fargo by 1.6 feet. The equivalent of 200,000 acre feet is the equivalent of 40,000 acres with five feet of water on it. Due to the large amount of water that would need to be placed in storage, the technical options were very limited. There isn’t much viable available storage farther upstream, as the land in the basin is very flat. Further, a much greater amount of storage would be needed to have the same effectiveness as the storage in close vicinity of the project, which would drive the costs up considerably and affect an even greater number of people.
Basin-wide retention is an important long-term water management strategy; however, it will not provide the level of flood protection achieved by the Diversion Project. For example, a study conducted by the USACE showed 400,000 acre-feet of storage is needed for a 1.6 foot stage reduction for the Red River at Fargo during a 100 year flood. Similarly, a study conducted by the Red River Basin Commission showed 270,000 acre-feet of storage is needed to provide a 2 foot reduction for the Red River at Fargo during the 1997 flood (<50-year). In contrast, the recommended Diversion Project will provide a 12 foot stage reduction for the Red River at Fargo during a 100 year flood.
The study team has found that storage alternatives, either as stand-alone measures or in combination with others, do not effectively or efficiently address catastrophic flood risk in the Fargo-Moorhead Metro area. Storage alternatives have the potential to reduce flood stages in the local area downstream of a storage site while they significantly increase flood stages upstream within the storage area. The stage reductions produced by flood storage are largest immediately downstream of the storage area and diminish with distance downstream of the storage area. If several storage sites were created over a large area, the system could have substantial cumulative benefits for relatively small and frequent flood events. However, the amount of storage that could be practicably implemented upstream of Fargo-Moorhead Metro area would not substantially reduce the risk in the Fargo-Moorhead Metro area from large infrequent flood events.
Furthermore, a system of flood storage sites would need to be implemented in many small increments over a very large geographic area over an extended period of time. Such a system would impact significantly more acres of land than the recommended plan and would be less effective in reducing flood risk in the Fargo-Moorhead Metro area.
The study team has found that other alternatives, such as diversion channels, are more efficient (provide more benefits at less cost) and more effective (reduce flood risk to a greater degree) than storage.
Several other current initiatives are considering flood storage in the Red River Basin, including two Corps of Engineers studies: the Red River Basin-wide Watershed Study and the Fargo-Moorhead and Upstream Area feasibility study.
As the design proceeds, minor adjustments to the alignment can be expected. Each alignment adjustment will be determined on a case-by-case basis. We can also consider major changes to the alignment, such as moving it west or south, during the design phase; however, we would still have to comply with current laws and policies to include the National Environmental Policy Act, the Clean Water Act and Executive Order 11988. (Executive Order 11988 requires agencies to minimize impacts on the floodplain). Changes may also require Congressional reauthorization.
The existing Sheyenne River diversion is really two diversion projects: the Horace to West Fargo diversion and the West Fargo diversion. The Fargo-Moorhead Metro diversion would incorporate and expand the Horace-to-West Fargo channel. From West Fargo north, the Fargo-Moorhead Metro diversion would run alongside the existing West Fargo diversion and be set far enough away so as to not affect the existing diversion. The Fargo-Moorhead Metro diversion would reduce risk in the cities of Horace and West Fargo from Sheyenne River floods more than the current Sheyenne Diversion does, and it will also reduce flood risk from Red River and Wild Rice River flood events.
The selected plan (LPP) would improve the Fargo-Moorhead Metropolitan Area’s ability to withstand excessive flows from Devils Lake.
Flows from Devils Lake could have both a water quantity and water quality impact on the Fargo-Moorhead area. If Devils Lake were to overtop, flow estimates for a controlled overflow are 3,000 cfs and flow estimates for an uncontrolled overflow with erosion are approximately 14,000 cfs.
If a North Dakota alignment diversion channel were in place, it would have the capacity to capture those flows during flood events and provide flood risk management benefits to the communities.