Rehabilitation of warmwater stream ecosystems following channel incision

Presented is a case study of two streams (watershed size, 12 and 14 km(2)) damaged by channel straightening and incision. One stream was stabilized using a metal sheet piling weir and dormant willow post planting, while the other was treated with a stone weir, stone toe bank protection and willow sprout planting. Fishes and their physical habitats were monitored for 1-2 years before construction and two to three years afterward. Willow planting was not successful, so canopy, bank vegetation, and woody debris density were unchanged. Pool habitat area increased from less than 5% to more than 30% of the total aquatic area. Fish species richness and diversity were unchanged, but species composition shifted away from patterns typical of shallow, sandy runs toward Fool-dwelling types, becoming more similar to a nearby lightly-degraded reference site. Median lengths of selected centrarchids increased following rehabilitation. Physical and biological response were more persistent for the stream treated with the stone weir and bank toe protection, possibly because the stone toe produced a more uniform longitudinal distribution of cover and pool habitats than the single weir. (C) 1997 Elsevier Science B.V.