Whitehead Saline Wetlands, north edge of Lincoln, Nebraska
Whitehead Saline Wetlands, north edge of Lincoln, Nebraska

Projects

Colonial Hills Park Water Quality Improvement Project

Project Client: City of Lincoln
Project Location: Lincoln, Nebraska
Project Categories: Streams

The stream reach in Colonial Hills Park is a tributary to Antelope Creek and is immediately upstream of Holmes Lake in Lincoln, Nebraska. The reach has suffered from stream bank erosion, significant streambed down-cutting, failing stormwater inlets and collapsing concrete flume sections of channel. Annual flooding of the adjacent park causes wide transport of gravel from an existing playground equipment structure. The stream continued to erode long sections of bank that caused bank collapsing on adjacent public land.

The design approach accounted for the urban setting of the park. After the fluvial geomorphologic analysis, the thalweg was shifted closer to its primary alignment to minimize further impacts to the adjacent private property and relocated to the historic preferential flow path through the park. Channel incision and bank erosion can be prevented through grade control structures and bank reshaping. These structures will prevent further incising and prevent meandering within the bed forming portion of the channel. Riprap drop structures were installed to minimize the erosive impacts from storm events due to limitations of a no-net increase in stream alignment. Stormwater inlets were repaired and plunge pools were installed to control high flow velocities from urban runoff. A water quality cell was installed at the downstream end. The cell is designed as a wide low-lying area just above normal channel flow levels. This will serve as a water quality feature and will help dissipate the energy of higher flow events while providing additional channel storage. Regrading and bank armoring was completed at a significant headcut surrounding the end of a concrete flume. Large sections of the stream reach were regarded to a 7’ wide channel bottom with 3:1 side slopes.

Localized riprap protection of low-flow liners and a culvert outlet was completed to prevent further bank erosion, scour and undercutting. A riprap stilling basin at the base of south low-flow dissipates energy of the water as it enters the channel. This stilling basin was designed so that it can also be used as a channel crossing during low flows. Construction of the water quality improvement project was completed in June 2007.


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