At a Glance

Ecological restoration returns dynamic hydrology and 60 acres of estuarine habitat to land long manipulated to support agriculture.

Project Description

Until it was diked and drained for agricultural use in the 1930s, the land on the southern side of the Svensen Slough, a side channel of the Columbia River, was a spruce swamp. Over time, as levees subsided and lowland floodplains regained some tidal connectivity, many areas became unsuitable for farming. Such was the case with a 60-acre site owned by Clatsop County and three private landowners. The site, which included land along three tributaries of the Slough—Bear, Mary’s, and Ferris Creeks—provided some habitat for several species of salmonids.

With funding from Bonneville Power Administration, the Columbia River Estuary Study Taskforce initiated a restoration of the site with the goal of enhancing habitat for juvenile salmon and other stream and riparian dependent species. For help in implementing restoration construction, CREST turned to Biohabitats.

The project involved breaching and removing sections of remnant levees along each creek. This included dewatering, excavating 30,000 CY of soil to create backwater channels, lowering the marshplain, placing large woody habitat structures, and removing failed and derelict culverts. Specialized low ground pressure equipment equipped was used for in-water work areas. The project included the removal of Invasive species, including reed canary grass (Phalaris arundinacea), English holly (Ilex aquifolium), Himalayan blackberry (Rubus armeniacus), and Poison hemlock (Conium maculatum). Over 90,000 native plant species were installed to enhance biodiversity. While accounting for sea level rise, the restoration restored important estuarine habitat, fish access, hydrologic flows, and nutrient cycling.

Details

Bioregion

Southern Rocky Mountain

Physiographic Province

Oregon Coastal Range

Watershed

Lower Columbia River

Expertise Areas

Coastal, Design & Build, Ecological Restoration, Water

Owner

Columbia River Estuary Study Taskforce

Location

Knappa, Oregon, United States

Project Team
  • Alfonse Excavation
  • Empo Bay Marine