Posted on November 6, 2024
NIOBRARA, Neb. — A joint research pilot project between the U.S. Army Corps of Engineers, Omaha District, the U.S. Army Engineer Research and Development Center and the Missouri Sedimentation Action Coalition was recently conducted on the Niobrara River in northeast Nebraska to test new technology designed to intercept sediment from the riverbed before it reaches Lewis and Clark Lake.
More than 50% of sediment deposited into the Missouri River reach that makes up the Lewis and Clark Lake delta comes from the Niobrara River. The spring-fed river travels along the northern edge of the Sand Hills of Nebraska and produces a nearly endless supply of sediment through bank, gully, riverbed, and overland erosion.
As a result, the water surface elevation of the Missouri River throughout the Lewis and Clark Lake delta has continued to rise since the lake was formed in 1955 causing increased flood risk, higher ground water levels and water quality and supply issues for nearby communities.
Engineers participating in the project tested a 12-foot bedload sediment collector to determine how much sediment could be captured from the Niobrara River before it reaches the delta.
The speedbump-shaped structure sits on the riverbed and captures sediment as it travels over it and into a trough where it is then pumped out of the river and captured in dewatering bags or large sediment management areas.
The bedload collector method is one of many management methods being considered for Lewis and Clark Lake. The U.S. Army Corps of Engineers and the Missouri Sedimentation Action Coalition hope to publish the “Lewis and Clark Lake Sediment Management Plan” in the next two years. The plan will include an engineering analysis on the various methods and recommend those that offer the greatest benefits at the lowest costs and with the least environmental impacts.
Overall, engineers consider the equipment and test highly successful.
“Under these conditions, the collector was effective, we’re very happy with the results,” said Paul Boyd, U.S. Army Corps of Engineers, Omaha District hydraulic engineer. “We’re pulling a lot of sand out of the river.”
Now, Boyd says the challenge is finding a use for the sediment that will offset the cost of removal. He says construction projects could be a potential option.
“Our long-term goal is to try and reduce the cost of harvesting and increase the beneficial use or the value of the sediment – we hope to kind of flip that paradigm and make it cost effective to move sediment” Boyd said.
The U.S. Army Engineer Research and Development Center, or ERDC, has been researching bedload sediment collection in support of river navigation for more than a decade. Recently, the center expanded its research to address reservoir sedimentation issues in collaboration with Corps districts like Omaha. They are also conducting research with the St. Paul District for reservoir sustainability, the St. Louis District for lead remediation and the Vicksburg District for port maintenance.
“We were able to fund the work because of the strong partnership with the Missouri Sediment Action Coalition and the association with the [Omaha District], which we like,” said Chuck Theiling, ERDC Environmental Lab research ecologist. “We also have the U.S. Geological Survey scientists helping us determine sedimentation patterns in the river and flow rates and such that will really support our research.”
Theiling says the success of the pilot project could lead to much bigger things.
“If we can take our estimate from this unit and scale it up to a larger unit – conceivably something that might span a whole channel – then we can try to collect most of the sediment going by.”
The research team is currently developing a proposal to return to the Niobrara River in late 2025 to further test the influence of bedform transport of sediment across the collector. They hope to use these tests to improve collection methodology and increase collection efficiency.
An overhead view of the Niobrara River bedload sediment collector pilot project near Niobrara, Nebraska Sept. 11, 2024. Engineers participating in the project tested a 12-foot bedload sediment collector to determine how much sediment could be captured from the Niobrara River before it reaches the Lewis and Clark Lake delta.
