In 2012, Habitat Restoration Sciences (HRS), Dudek’s wholly-owned habitat construction subsidiary, constructed the first phase of restoration at Cold Creek located on California State Parks (CSP) land near Donner Memorial State Park.
The goals were to improve riparian habitat and reduce erosion impairing the water quality of the creek feeding into the Truckee River.
Cold Creek had incised due to gravel mining and channelization. It was continuing to erode with little riparian habitat, according to CSP geomorphologist Cyndie Walck, who supervised the project to excavate more than 13,000 yards of
material and construct a new floodplain. The project was done under contract with the Truckee River Watershed Council (TRWC), which coordinates, funds, and implements restoration projects in the region’s watershed.
Just after floodplain construction was completed, a severe storm swept through the watershed, re-activating a “head cut” in the Cold Creek streambed and raising the possibility of channel bed instability. A head cut, the geomorphological term for an abrupt vertical drop in a creek streambed, causes erosion as the water flow incises (down-cuts) and ultimately removes streambed material to lower the creek grade.
The Cold Creek head cut presented several issues to CSP and TRWC. First, it threatened to undo the previous year’s water quality improvement project of repairing failing banks to reduce erosion. Second, repairing the head cut required meeting a tight deadline of completing work before October 15 when construction activity must stop for the season in the region.
The CSP prepared a design for a series of boulder weirs to control the creek grade and prevent the head cut from migrating further upstream into the restored reach. The design also called for constructing engineered streambed material riffles between the weirs to stop fine sediment erosion.
To complete repairs within the three-week window, and before the construction activity cut-off, TRWC contracted with HRS, Dudek’s native habitat landscape contracting group. Mark Girard, HRS president, said two elements were key to successfully completing the project.
Quick Access to In-House Team
The HRS construction crew had to be supplemented with an aquatic ecologist to oversee fish relocation, and a river engineer to “field fit” the design drawings to implementation. “In the Sierra’s at this time of year, there can be a waiting list for river specialists with the right technical skills,” Girard said. “Because HRS and Dudek work seamlessly, we got immediate support from Dudek’s aquatic ecologists and river engineers. The ability to put the right experts on the project in a timely way is critical under a tight deadline.”
Rapidly Adapting to Field Conditions
“Working in a river is a dynamic environment,” Girard said. “Adapting to unforeseen issues is almost always a given.”
That proved to be the case with the effort to “dewater” 550 feet of the creek to allow repair work. Dudek’s Loren Roach said damming the creek alone proved impossible because the water traveled sub-surface and popped up on the other side of the dam. “The solution was keeping the diversion dam in place and utilizing a dry well with an electric submersible pump and pumping it 24-hours a day,” he said. “While we had to shift from the original plan, we had the creek by-passed in a day and didn’t lose any time on our tight construction schedule.”
Experience also contributes to quick field adaptation, Girard said. “We had seen similar issues with recent work on Blackwood Creek in the Tahoe area, as well as other creek projects,” he said.