PORT ANGELES — After a dam was removed from the Olympic Peninsula’s Elwha River, about 3.3 million cubic yards of sediment from the dam lakes streamed down the river between November 2012 and September 2013, according to U.S. Geological Survey estimates.
The result? A changing river mouth and new beaches.
The sediment released by the removal of the dam has built up so much at the river’s mouth that areas that were underwater before the dams were removed are now land for hikers, The Peninsula Daily News reported Sunday.
“There has definitely been some added land, (some) new land created,” said Ian Miller, a coastal-hazards specialist with Washington Sea Grant. “The river mouth is just changing dramatically all the time.”
Millions of cubic yards of sediment have been released from the bottom of the lakes that once bore the names Aldwell and Mills as part of the $325 million Elwha River dam-removal and restoration project begun in September 2011. The 108-foot, century-old Elwha Dam, which once cradled Lake Aldwell, was completely removed by March 2012, while all but 30 feet remain of the once-210-foot Glines Canyon Dam.
Miller, who has been monitoring changes at the river mouth since the dam removal began, said he will be part of a seven-person team the U.S. Geological Survey is organizing at the end of April to gather the most recent estimates of sediment built up there.
Miller said maybe 1 million cubic meters, or 1.3 million cubic yards, of sediment could have been added to the mouth this winter and early spring thanks to a wetter-than-normal February, another notch taken out of Glines Canyon Dam earlier this year and spring snow melt in the Olympic Mountains.
As sediment continues to course down the flowing Elwha, Miller said, the only sure thing about how the mouth looks is that it will change, likely for years to come.
Miller was at the river’s mouth Friday with University of Washington senior Sarra Tekola. Tekola was taking samples of sediment accumulated there to test how much carbon is in the material.
The pair trudged through thick, slate-gray mud on the blustering day, almost losing a boot or two to the sucking muck.
“There are definitely places (that) are softer, and you just have to be sort of careful and test your footing before you put all your weight on it,” Miller said.