Dam gone, nature rebuilds Elwha River beach
After a 100-year retreat, the beach at the mouth of the Elwha River is making a comeback.
Seattle Times staff reporter
Every few weeks, scientist Ian Miller heads down to the delta of the Elwha River to have a close look at the beach. And what he saw beginning last April surprised him: a bit of sand.
While that may not sound like much, Miller knew he was seeing something more. A month earlier, contractors had finished taking out the last of Elwha Dam. Now here it was on the beach: sediment set free along with the river.
That bit of softness afoot on the eroded, cobble beach was a first taste of the restoration benefits of Elwha dam removal, and the sweep of its reach: all the way to the river's mouth.
By May and June — during some of the lowest daylight tides of this year — Miller saw even more sand on the beach, growing in a sweep to the east, with the prevailing current.
A coastal-hazard specialist based in Port Angeles for Washington Sea Grant, Miller is continuing his work, to learn how, if and when this beach may be altered by sediment set loose by dam removal.
Taking the dams out of the Elwha isn't only about allowing fish to come back up river to their spawning grounds for the first time since two dams were built on the Elwha without fish passage, beginning in 1910.
The $325 million Elwha River ecosystem restoration begun last September is also about allowing wood and sediment to flow down the river from its watershed.
The dams strangled the river's natural transport capacity, and hoarded the gleanings from its watershed in the dams' reservoirs: logs, root wads and other woody debris, and about 24 million cubic yards of rocks, sand, gravel and fine sediment.
As the dams come out, the river is expected to mobilize about one-quarter to one-third of that sand and gravel trapped in the reservoirs and about one-half to two-thirds of the fine sediment, according to Tim Randle of the U.S. Bureau of Reclamation, which is directing management of the sediment during dam removal.
It's the largest ever controlled sediment release in a dam-removal project anywhere in the world.
Some of the material will stay right in the lake beds. Some will settle in the river bottom. But some of it will be transported all the way to saltwater, and build up the beach and seafloor. And to some, it's a welcome change.
Today, the beach can erode 12 feet a year on average in some places, according to Miller. Members of the Lower Elwha Klallam Tribe talk about their elders clamming on beaches that have little or no sand today, and running cattle on land east of the river mouth that has since washed away.
Jon Warrick, geologist at the U.S. Geological Survey's Pacific Coastal and Marine Science Center at Santa Cruz, Calif., notes the cobble beach exposed at low tide at the Elwha delta today is inconsistent with the tribe's oral history of clamming on the beach. And that, Warrick notes, is probably the result of coastal erosion related to the impacts of the dams on sediment flowing to the coast. And the rate of erosion is increasing.
Dam removal is expected to help reverse some of that trend.
How much, nobody knows. The Strait of Juan de Fuca where the Elwha meets the saltwater has a ripping current. The river has also been channelized and diked in its lower reaches, altering its ability to move sand and other material naturally into the estuary and near shore.
To track the changes already under way, scientists are trying a bit of everything. Farther offshore, scientific divers with the USGS, the tribe and Sea Grant were underwater last month, taking stock of transects they set on the sea floor last year before dam removal began.
They saw portions of the underwater ecosystem were inundated by the sediment plume pouring from the Elwha; anemones and tube worms that before dam removal were surrounded by bare substrate last year are nestled amid soft sediment now.
As for Miller, he is tracking the beach with a variety of approaches. Using digital photography, he can document the grain size of the beach, and how it is changing over time.
He has also deployed fleets of what he calls "smart rocks" — river cobble, pebbles and small boulders tricked out with radio tags embedded in the rock — tossed overboard in the river or snugged in the beach. He dials in the signals with an antenna and receiving device he carries in a backpack to see where and how far the rocks move under different weather conditions.
Still to be seen are the results this first winter with the lower dam out, particularly if, unlike last winter, there is an active storm season. And yet to come is the big bang of sediment when Glines Canyon Dam, a few miles upriver, is completely out by next May.
The real story on dam removal will only be revealed over time, Miller said: "We still don't know the long term effects."
But there's no doubt change is already afoot.
"It's changing all the time," Miller said of the beach. "That was one of the questions we had, was would [dam removal] have a response on the beach. What this shows is that sediment can and will make it onto the beach. What I am seeing is sand, and it's new sand."
Lynda V. Mapes: 206-464-2736 or email@example.com. On Twitter @lyndavmapes.