AN INTEGRATIVE APPROACH TOWARDS UNDERSTANDING ECOLOGICAL RESPONSES TO DAM REMOVAL: THE MANATAWNY CREEK STUDY¹

Abstract

Dam removal has been proposed as an effective method of river restoration, but few integrative studies have examined ecological responses to the removal of dams. In 1999, we initiated an interdisciplinary study to determine ecological responses to the removal of a 2 m high dam on lower Manatawny Creek in southeastern Pennsylvania. We used an integrative monitoring program to assess the physical, chemical, and biological responses to dam removal. Following removal in 2000, increased sediment transport has led to major changes in channel form in the former impoundment and downstream reaches. Water quality did not change markedly following removal, probably because of the impoundment's short hydraulic residence time (less than two hours at base flow) and infrequent temperature stratification. When the impoundment was converted to a free flowing reach, the composition of the benthic macroinvertebrate and fish assemblages in this portion of Manatawny Creek shifted dramatically from lentic to lotic taxa. Some fish species inhabiting the free flowing reach downstream from the dam were negatively affected by large scale sediment transport and habitat alteration following dam removal, but this appears to be a short term response. Based on our observations and experiences in this study, we provide a list of issues to evaluate when considering future dam removals.

Changes in benthic algal communities following construction of a run-of-river dam

“…1C) from February 2003 to August 2006. Our sampling approach was based on a modified Before-AfterControl-Impact (BACI; Green 1979) design for assessment of disturbance (Bushaw-Newton et al 2002). We sampled benthic algae at 3 upstream control sites (JC1-JC3) and 2 downstream impact sites (JC4 and JC5) (Fig.…”

Dam removal and anadromous salmonid (Oncorhynchus spp.) conservation in California

“…However, dam removal may present benefits to other taxa and river ecosystems as a whole. For example, Bushaw-Newton et al (2002) found that communities of aquatic insects became more diverse upon dam removal in Manatawny Creek. Freshwater mussels were also expected to benefit from dam removal through the recolonization of upstream habitats by host fishes.…”

Planning and implementing small dam removals: lessons learned from dam removals across the eastern United States

“…Recommendations for dam removal planning outlined by Bushaw-Newton et al (2002) in their thorough assessment of dam removal on the Manatawny Creek, Pennsylvania advocated for similarly rigorous stakeholder engagement and removal impact analysis when deciding whether or not to remove a dam, when designing the dam removal, and for subsequent dam removal impact monitoring.…”