Well here comes the landscape we’ll be living with on the Elwha. About 60 percent of the sediment trapped behind the dams will stay behind, in stepped down terraces of material that was trapped behind the dams. As of about a week ago, Lake Aldwell, behind Elwha Dam, was completely gone, following the completion of demolition of the dam in March.
Lake Mills is also disappearing, as Glines Canyon Dam comes down, with about one third of the dam already gone. It is expected to be history, too, by about this time next year. So what will remain? I took a walk around the landscape just upstream of former Elwha Dam over the weekend. It was a spectacular, otherworldly experience. Anyone with the slightest interest in photography ought to get out to have a look.
Stumps of trees cut when the reservoir was filled behind Elwha Dam wear sediment hats. The river, back in its channel, is carrying high sediment loads now that the reservoir behind Elwha Dam is gone. Fine particles that used to settle out in the reservoir are now mobilized in the water, and carried on down the river. The uniform ashy gray color created by the coating of silt on every surface, gives the landscape and eerie, lunar feel.
The sound of the river is back, where there used to be only a lake. Here the Elwha River rushes through what used to be Lake Aldwell. About 60 percent of the sediment trapped behind the dams — some 24 million cubic yards — is going to stay behind in the landscape, just as you see here. The rest will sluice out to sea. Nature, and an active revegetation effort directed by the National Park Service is hoped to green up the landscape in time.
The river below former Elwha Dam is carrying about 50 times more sediment than usual, according to Tim Randle at the U.S. Bureau of Reclamation, who is directing the management of the sediment in the Elwha River restoration project. The spike is sediment is due to the disappearance of Lake Aldwell, which used to settle out some of the material that’s cut loose as the dams have been demolished. Most of the sediment in the river right now is coming from behind the former Elwha Dam. Much of what is coming out now is fine silt and clay.
Winter storms, and time are bound to keep sculpting the soft terraces of sediment left behind as the reservoirs drop. But much of what you see out in the former lake bed of Lake Aldwell is what we are going to get, as far as the appearance of the landscape. Try to imagine this view, greened up with trees and shrubs. It’s not that different from the views of say the terraced uplands at Goblins Gate, above the dams:
The goal of the Elwha restoration was to drop the reservoirs behind the dams gradually, so that the sediment trapped behind them would be eroded by the river. About 40 percent of the material — fines, sand, cobble, rocks, and gravel, will move downriver. The rest will stay behind. The hope was to leave a natural looking landscape behind, especially as plants regrow.