Project Purpose
The existing Little Floyd Lake dam was constructed in 1936 and acts as a barrier to fish migration upstream into Little Floyd Lake, the headwaters of the Pelican River. We propose to modify the existing dam and provide fish passage by installing a rock arch rapids which will improve opportunities for recreation, fish and wildlife habitat and dispersal, as well as provide a permanent
fix to the aging fish barrier structure.
A rock arch rapids is a structure that mimics shallow natural rapids in rivers that can be traversed by fish moving up and downstream. While modification of the dam into rock arch rapids will benefit all aquatic species moving along the channel, this structure will be particularly useful in aiding the MN DNR’s goal of reintroduction of sturgeon, the MN DNR began stocking them in downstream Detroit Lake in 1997, and the rock arch rapids would create suitable spawning habitat for them. In addition, this project will aid in improved fish movement and reproduction as outlined in the MN DNR’s Red River of the North Fisheries Management Plan (2017-2027) and the Pelican River Watershed District Revised Water Management Plan (2020-2029). Even though this project covers less than one acre of land, it will benefit the 14,790 acres of lakes and 84 river miles in the entire Pelican River Watershed by restoring connections that existed prior to dam building.
Questions About Lake Levels
Will my lake level change as a result of this project?
No. Your lake is a designated public water. That means the runout elevation and performance of the dam will be maintained by any replacement structure. This is a Minnesota statutory requirement. A consulting engineer has submitted modelling as part of project permitting, demonstrating compliance with this requirement.
Similar projects have been implemented in a wide diversity of locations around the state and are designed by professional engineers contracted specifically for the work. Lake levels have not been impacted by these projects. In the simplest sense, we replace one weir (dam) with another (top step of the rock-arch rapids) that maintains the critical dimensions and runout elevation. There are many local examples of similar projects, including Muskrat, Pelican, Lizzie, Prairie, Little Pine, Big Pine, Rush, and Otter Tail Lakes
Per project design plans, the dam sill was not removed during construction as it maintains the 1355.0 NAVD 1929 elevation set by the Dam Safety Program records. The exposed side wall concrete was removed to be even with the sill. In addition to meeting design requirements and maintaining the original dam elevation, there is now a first downstream boulder weir also set at the 1355.0 runout elevation for Little Floyd as a redundant runout elevation control.
How can the project move from a box-like rectangular cross section of concrete walls to an open channel trapezoidal cross section, yet have similar water behavior over the dam?”
The project post-construction runout elevation (1355.0) and hydraulic performance must be maintained. Hydraulic performance is the amount of water leaving the lake at a full range of upstream high and low levels using historical lake level data. Performance is influenced by outlet runout elevation (legally fixed, red dots), channel geometry (see photo with green dots, simplified for example), downstream channel geometry, and the road culvert geometry/elevations. Prior to project permitting, all of these factors are placed into a flow model, simulating the new structure. The performance of the new structure is iteratively improved. Channel dimensions (green dots) are altered to ensure that the performance of the new matches performance of the old.
Construction Phase Water Levels
Construction Lake Level Monitoring – 11/4/2024 to 11/8/2024.
Lake levels were recorded and pictures were taken AM and PM during construction to verify lake levels throughout the construction. The staff gauge photos demonstrate pre- and post-project lake elevations were/are the same. Note the water flowing over the dam sill pre and post construction.
Per project design plans, the dam sill was not removed during construction as it maintains the 1355.0 NAVD 1929 elevation set by the Dam Safety Program records. The exposed side wall concrete was removed to be even with the sill. In addition to meeting design requirements and maintaining the original dam elevation, there is now a first downstream boulder weir also set at the 1355.0 runout elevation for Little Floyd as a redundant runout elevation control.
Construction Progress
Project Funding
How is this project funded?
The Pelican River Watershed District applied for grant funds to construct this project.
MN DNR Grant – $ 156,400
PRWD Local Funds Match – $18,000
Project Total = $174,400
Funding Background
Thirty-three percent of the sales tax revenue from the Clean Water, Land and Legacy amendment is distributed to the Outdoor Heritage Fund. Those funds “may be spent only to restore, protect, and enhance wetlands, prairies, forest and habitat for fish, game, and wildlife.” Land acquired with Outdoor Heritage Funds must be open to public hunting and fishing during the open season in accordance with the state constitution.
