The upper Jefferson is a much-braided, meandering river and floodplain system that supports productive farm fields, extensive cottonwood groves, rich meadows, and abundant wildlife. The river creates diverse habitats as it naturally shifts back and forth across the Jefferson Valley, forming oxbows and swamps of various depth and age. Shifting channels and natural flooding facilitates the germination of cottonwood seedlings. Individual cottonwood groves are often germinated from a single flood event and tend to be of uniform age. The upper Jefferson extends from the confluence of the Big Hole and the Beaverhead rivers approximately 44 miles downstream to the community of Cardwell.