Rehabilitating aquatic ecosystems in developed areas

Abstract

Efforts to restore watershed and aquatic ecosystem processes in urban areas are constrained by municipal infrastructure: bridges, dams, roads, buildings, and stormwater and sewage treatment systems (Carpenter et al. 2003; Booth 2005; Bernhardt and Palmer 2007). Consequently, rivers, streams, and estuaries in developed areas cannot be fully restored to unimpaired conditions, but in some cases can be rehabilitated to support salmonid populations. Therefore, the terms rehabilitation and enhancement are preferred over restoration when referring to improving environmental conditions in developed areas (Box 13.1; mitigation is addressed in Chap. 15). The general goals of watershed rehabilitation actions are to improve ecosystem processes so that they promote and sustain habitat connectivity, riparian vegetation, water quality, and streamflow regimes (Roni et al. 2002; Beechie et al. 2008). Enhancement approaches are used as short-term, stream-reach measures that often provide only temporary local benefits to aquatic ecosystems until self-sustaining, habitat-forming processes have been rehabilitated. Most rehabilitation and enhancement techniques (e.g., floodplain reconnection, meander construction, fish passage improvement) are implemented throughout the landscape and are not unique to urban areas but may need to be modified for these areas to account for infrastructural, social, or regulatory constraints.