The South Umpqua River is located in Douglas County in southwestern Oregon. The South Umpqua River is one of two main tributaries to the mainstem Umpqua River, which empties into the Pacific Ocean through Winchester Bay in Reedsport, Oregon. The South Umpqua River is approximately 115 miles long, but when added to the length of the mainstem Umpqua River (approximately 111 miles), it is considered the longest undamed segment of river on the west coast. The South Umpqua River drains a portion of the Cascade Mountain Range east of Roseburg, and the river’s headwaters originate in the protected Umpqua National Forest.
In total, the United States Forest Service (USFS) owns and manages 28% of the total land within the basin; this land is uniformly clustered around the upstream reaches of the river. An additional 22% of the watershed area is managed by the Bureau of Land Management (BLM). Downstream reaches of the South Umpqua River Basin are dominated by private land ownership; 49% of the basin is privately owned. The Xerces Society for Invertebrate Conservation has identified the South Umpqua River as a high priority stream for both western ridged (Gonidea angulata) and western pearlshell (Margaritifera falcata) mussel surveys. In addition, the South Umpqua River also hosts wild runs of chinook salmon, coho salmon, steelhead, and lamprey in addition to resident populations of trout and invasive small mouth bass.