1100 Jadwin Ave.
Suite 250
Richland, WA 99352

Army Corps of Engineers Invasive Species Vegetation Survey

Understanding baseline conditions in a changing climate is essential to long-term management.

On behalf of the U.S. Army Corps of Engineers, Walla Walla District (Corps), Freestone developed work plans and conducted two multi-phased surveys of native, naturalized, and invasive vegetation species and canopy coverage, with an emphasis on documenting the occurrence of noxious weeds. This inventory of plants adds detail to existing broad cover type mapping in order to implement the Corps’ Integrated Pest Management Plan (IPMP) effectively. This inventory is also important for the Corps to better support the Lower Snake River Fish and Wildlife Compensation Plan (LSRFWCP). In order to complete mitigation under the LSRFWCP, the Corps is instituting native riparian habitat plantings coupled with removal of noxious weeds and other invasive plant species in selected areas. The survey was performed on Corps managed lands (10,125 acres) along the Dworshak Reservoir and Clearwater River in Idaho, and over 50 river miles of Lower Snake River shoreline between Lower Granite Dam and Lyons Ferry State Park, Yakima River delta and portions of the Columbia River in Washington State.

In collaboration with the Corps, Freestone field personnel identified survey polygons to represent the variety of habitats present in the study area. The first phase involved a visual estimate of plant species within pre-selected areas represented by unique canopy type. The second phase involved a traditional plant survey using transects and Daubemire plots to quantitatively assess species occurrence. Inventory data was compiled into a geodatabase format to be used to support the Corp’s integrated pest management program. This vast survey involved boat-only access to remote areas of Washington and Idaho. Survey polygons were accessed by vehicle, foot, and boat for five weeks. For most representative results, the survey was conducted during maximum vegetative growth for key species. This often posed challenges of accessibility due to overgrowth, further compounded by uneven, steep canyon terrain, densely vegetated delta wetlands, and abundant presence of potentially hazardous wildlife. Surveys were conducted in pairs for safety. The Corps was impressed with Freestone’s efficient performance of the field work, high quality of technical reports, and safety documentation. The Corps used the survey results to develop and augment scope for subsequent similar studies; identify practical pest management strategies; and complete mitigation LSRFWCP. Freestone is preparing for another similar survey to be conducted in spring/summer 2017.

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