In an effort to stabilize shorelines, protect cultural sites and improve habitat for fish and wildlife, Corps engineers, biologists and environmental scientists have repurposed native coyote willow found below the Mill Creek Diversion Dam at Rooks Park in Walla Walla.
Coyote willow is one of the native species growing in the stilling basin of the Mill Creek Diversion Dam. Cutting the young willow whips back is necessary to maintain channel capacity. However, instead of being thrown out, those willow whips can be replanted in other areas where they are needed.
“We’re getting a couple birds with one stone,” Brad Trumbo, fish and wildlife biologist for the Walla Walla District corps of Engineers, said. “We take these willow whips from this area, which is kind of a dam safety concern having all of this vegetation in here, as far as channel capacity. Then, we’re going to take them down stream to a cultural site and we’ll be able to stabilize a bank that is exposing potential cultural resources and artifacts.”
There are several factors which can lead riverbanks to erode. Exposed, cut banks can often attract cliff swallows, which burrow into the bank and weaken it further. Fluctuating water levels soak into the soil, or into the cliff swallow nests, leading to soft soil and promoting further erosion.
“We’re going to take these whips and we’re going to plant them in along the toe of that bank. They’re good for erosion control, as a native species,” Trumbo said.
Minimizing bank erosion can protect sites by preventing potential cultural artifacts from being unearthed while also maintaining a stable riverbank that can be used by fish and wildlife.