Data Sources and Evaluation
LIDAR and aerial photography were used to identify areas with potential for restoration in the mainstem Chehalis, South Fork Chehalis River, and Skookumchuck River. No LIDAR data are available for the Newaukum River. Existing geographic information system (GIS) layers of fish habitat and limiting factors, including existing culverts, were used to make maps of project locations. The side channel GIS layer was created based on this assessment. Data sources for the layers included: • • •
2.1
LiDAR – Puget Sound LiDAR Consortium, 2002 Aerial – U.S. Department of Agriculture (USDA), National Agriculture Imagery Program, 2009 WAUs – DNR, 2006
Identification of Potential Projects
Potential projects were identified based on an assessment of the common limiting factors within WRIA 23. Seven limiting factors have been identified that have impacts on both physical processes within the watershed and salmonids (Grays Harbor County Lead Entity Habitat Work Group 2011): •
•
•
• •
•
Fish Passage Conditions: Poor fish passage conditions typically result from improperly sized water crossing structures and result in loss of access to spawning and rearing habitat. Floodplain Conditions: Degraded floodplain conditions typically result from floodplain filling, dike and levee construction, and streambank armoring and result in loss of backwater and side channels used for spawning, rearing, and refugia during high flows. Riparian Conditions: Poor riparian conditions typically result from intentional removal of vegetation, usually associated with land use conversion or timber harvest, and results in limiting shade, nutrients, and large woody debris availability. Large Woody Debris: Lack of large woody debris usually results from poor riparian conditions and removal of woody debris from the channel. Water Quality: Poor water quality typically is associated with water temperature, suspended solids, and chemical composition usually resulting from poor riparian conditions and stormwater runoff problems. Water Quantity: Low summer flows typically result from altered hydrology (landscape changes that allows rapid surface runoff).
Draft Phase 1 Report Chehalis River Salmonid Habitat Enhancement Plan
4
February 2012 100705-01.02