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.
Perceptions of sea-level rise in urban, environmental justice (EJ) communities are poorly understood. These communities' long-term vulnerability may increase as a result of the interaction of sea-level rise and legacy pollution. This article presents research on experience and perceptions of sea-level rise, flooding, legacy pollution/contamination, and health in an EJ community in northern Delaware. The community is in close proximity to documented brownfields and other hazardous sites, and is located where there are long-term projections of water inundation due to sea-level rise. Researchers administered quantitative surveys at local events that measured knowledge and concern for these issues; conducted focus groups that enabled a deeper understanding of survey results; and examined community perceptions relative to existing policy tools, including sea-level rise inundation maps and documentation of contaminated sites. The mixed-method approach created a baseline of perceptions on pollution, flooding, a health-environment connection, and sealevel rise. Key findings include the value of experiential knowledge of local flooding to improve efficacy of future policy prescriptions, and how a lack of knowledge of sea-level rise, coupled with great concern for it, might be explained by longtime familiarity with flooding issues in the community.
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