These stumps along the Sandy River are all that remain of trees buried in a lahar in 1780. In January, the river changed course, washing away the sediments and exposing the centuries-old trees.
Campers, hikers and other park visitors are in for a surprise at 1000-acre Oxbow Regional Park this summer
While Northwest residents sheltered inside during a wet winter and spring, nature was at work re-engineering the northeastern shore of this spectacular wilderness park in the scenic Sandy River Gorge. Since late 2009, the Sandy has been changing course, redirecting its flow against a 65-foot-tall volcanic sand embankment. The park’s campground, amphitheater and trails have been located atop that embankment. This past winter, the erosion was severe, completely washing away the amphitheater and causing other changes.
An ancient and ongoing story
To trace this story back to its origins, swim upstream to the Sandy’s headwaters in the glaciers and snowfields on Mount Hood’s southwestern flanks. There, hundreds of years ago, a high volcanic vent near Crater Rock began to ooze a sticky type of lava known as dacite.
This toothpaste-like lava mounded into a gigantic, doughnut-shaped structure called a lava dome. In 1780, the precariously perched dome collapsed under its own weight, sending a massive avalanche of hot rocks into the glaciers and snowfields below.
Snow and ice in the path of this hot torrent melted instantly, in turn sending an enormous volcanic mudflow (a lahar) down the mountain. The sand, gravels and other sediments in the flow came to rest in the upper reaches of the Sandy River basin. In subsequent winter storms over the decades, the materials were carried downstream to the Sandy’s confluence with the Columbia River, and upstream of that, to the location of today’s Oxbow Regional Park.
As the volcanic sand filled the valley from wall to wall, the forest of ancient Oxbow was buried alive and largely upright. For years, visitors to Oxbow have hiked, slept and barbecued on top of this forest buried 50 feet below the surface. But after events of the past two winters, the river has carved hundreds of feet from its 2009 banks, excavating sand from the centuries-old flows. While some human-built structures have disappeared, the buried forest has re-emerged and can be seen in ghostly stumps that loom from the ash gray sand.
What’s next for Oxbow
Oxbow is still open to visitors, with some changes in facilities and programs. Meanwhile, park managers, Metro scientists and outside consultants are assessing what the future may bring if the Sandy River continues to carve into its west bank and displace Oxbow’s visitor facilities.
Justin Patterson, Metro parks director, says bank stabilization with riprap or retaining walls is unlikely. It wouldn’t be an appropriate way to react to nature doing what nature does. “It’s a natural and scenic river, and there are certain values that come with that,” he says.
What is clear is that the park will continue to host visitors who come to hike in the old growth, sleep in the woods surrounded by the quiet sounds of a forest at night, attend nature programs, and marvel at the ancient ritual of the salmon’s return each fall to the life-giving and ever-changing Sandy River.
What you’ll find this summer at Oxbow
While Oxbow Regional Park remains open, the altered course of the Sandy River has brought some changes:
Park roads. The park entrance road is unchanged. The one-way entrance road to the campground has changed, since parts of it are now within a few feet of the riverbank. It is now a walking trail; the former one-way campground exit road is a now a widened, two-way road that serves both incoming and outgoing traffic.
Trails. The riverside trail upstream of the boat ramp is now closed. Other trails remain open.
Campground. The campground reopened in May. Last year, Oxbow had 67 campsites; this year there are 59 sites; sites 2 through 9 have been decommissioned since they are too close to the eroded riverbank. One of the two restroom and shower facilities had to be torn down since it was on unstable ground near the bank; the other facility remains, along with pit toilets and added portable toilets. As before, the campground is a first-come, first-serve facility.
Amphitheater. The old amphitheater is gone. Only the benches could be saved before the river chewed away the section of riverbank on which it was located. A temporary amphitheater is located near the old campsite 3; campers use the decommissioned campground entrance road to access it.
Picnic shelters. They were not affected and remain open.