Metro has acquired a 50-acre site just north of Wilsonville that protects unique features of the Missoula floods, which shaped the region’s landscape near the end of the last Ice Age.
A series of floods about 15,000 years ago swept through the Willamette Valley when the waters of Missoula Lake broke through an ice dam. The floodwaters sent boulders, soil and debris from Montana, Idaho and eastern Washington into the region.
The new acquisition includes a 3.5-acre kolk pond, created by whirlpools that scoured out deep areas. Flanking the pond are basalt hills called hummocks.
“The kolk pond and basalt hummocks illustrate the force and footprint of the Missoula Floods,” said Curt Zonick, a senior natural resources scientist at Metro who is leading restoration efforts at the site. “This is really our best acquisition in the Tonquin area to tell the story of what the Missoula Floods did.”
Kolk ponds are rare in the greater Portland metro region because of development, making this acquisition even more special, said Ryan Ruggiero, a real estate negotiator at Metro who worked on the acquisition.
“It’s always been a high-priority site,” he said.
The site also includes Oregon white oaks, Pacific madrones and rare wildflowers. The habitat supports Northern red-legged frogs and a variety of wildlife.
Part of the new acquisition is adjacent to Metro’s Coffee Lake Creek Wetlands, a 233-acre natural area. Metro’s North Coffee Lake Creek Wetlands, a 27-acre natural area, sits a short distance north.
Combined, the area helps connect an important swath of habitat between the Tualatin and Willamette Rivers that native plants and wildlife rely on to safely move between different areas to access food and shelter and to breed.
Initial restoration work at the site will include removing invasive plants, such as Scotch broom, Zonick said.
The new acquisition cost $1 million. The money came from the natural areas bond measure that voters approved in 2006. Metro Parks and Nature works to protect water quality, fish and wildlife habitat and provide opportunities for people to experience nature close to home.