Flowing northwest from the northern flanks of the Calapooya Mountains in Douglas County, Big River enters Lane County about 1 mile (1.6 km) downstream from the source. Box Canyon enters from the right at about river mile (RM) 9 or river kilometer (RK) 14. Big River receives Boulder Creek from the left, then Edwards Creek enters from the right at about RM 6 (RK 10). After receiving Bar Creek from the left and Martin Creek from the right, Big River meets Little River to form the Coast Fork Willamette River about 40 miles (64 km) from where the larger stream meets the Middle Fork Willamette River to form the Willamette River.[3]
^Source elevation derived from Google Earth search using GNIS source coordinates.
^ abcdUnited States Geological Survey (USGS). "United States Geological Survey Topographic Map". TopoQuest. Retrieved July 26, 2010. The maps, which include river mile (RM) markers for the lower 11 miles (18 km) of the river, cover the following quadrants from mouth to source: Harness Mountain, Burnt Mountain