CLARK FORK — Momentum is gathering behind a costly but vital project to combat erosion of the Clark Fork River Delta.
Operation of the Albeni Falls Dam on the Pend Oreille River for the last 57 years is causing the delta to erode at a rate of about 5-8 feet per year, according to Idaho Fish & Game biologist Kathy Cousins.
“We’re talking about a couple hundred acres at least,” Cousins said, referring to the total amount of erosion since the dam’s installation.
The delta provides vital habitat for resident and migratory wildlife but also provides another crucial benefit.
“It’s also an area that serves to clean water as it passes through. It improves water quality,” Cousins said.
The ambitious restoration project involves protecting shorelines from washing away through a combination of hard and soft engineered structures and creating barrier islands to protect existing islands. A portion of the delta islands that are currently submerged will be raised to restore and expand wildlife habitat.
The project also seeks to increase wetland habitat diversity and to capture woody debris and encourage sediment deposition in the delta, possibly by altering the log boom system to divert timber into the restoration area.
The work is slated to start in the fall of 2013, although a design team is gathering next month to begin firming up plans.
“It’s a very ambitious schedule, but we have to do this because there is a little bit of urgency. Every year that we do not do the work, we’re losing more wildlife habitat,” Cousins said.
A number of the lessons learned in restoring the Pack River Delta will be applied to restoration of the Clark Fork Delta. They include rock and log vanes to direct water away from shorelines and the use of vegetated rip-rap breakwaters.
A geo-tube breakwater was installed in the Pack River Delta, but that feature won’t be used in the Clark Fork Delta because of cost. It’s also lacks enough stout to effectively guard the delta, Cousins said.
The work is preliminarily estimated to cost up to $6 million and will be funded through Bonneville Power Administration dam mitigation funding and re-licensing agreements with Avista for the Noxon Rapids and Cabinet Gorge dams.
“It’s not going to be cheap. It’s going to be expensive,” said Cousins.