Geomorphic control of persistent mine impacts in a Yellowstone Park streamand implications for the recovery of fluvial systems

A half-century after mine closure, metal contamination from sulfide ore min ing in the headwaters continues to impair riparian vegetation and aquatic m acroinvertebrates along Soda Butte Creek, Yellowstone National Park. A tail ings dam failure in 1950 emplaced metal-rich sediment at high flood-plain l evels, above 50 yr to 100 yr flood stages in 1996 and 1997. These large nat ural floods removed only a small part of the contaminated sediment through bank erosion; they also failed to lower in-channel Cu concentrations, becau se increased erosion of mine waste during high hows balances increased inpu ts of uncontaminated sediments, generating no net change in concentrations. Geomorphic processes controlling movement of contaminated sediments indica te that mine impacts will persist for centuries in Soda Butte Creek and imp ly long-lasting impacts in similarly affected streams worldwide.