SS3.21 Deconstructing Rivers: The Ecological, Geomorphic, and Social Consequences of Dam Removal
Date: Thursday, June 13, 2002
Time: 11:30:00 AM
Location: Colwood
 
DoyleMW, Purdue University, West Lafayette, IN, USA, mdoyle@purdue.edu
Pizzuto, J, , University of Delaware, Newark, DE, USA, pizzuto@udel.edu
 
CONTRASTING TRENDS OF GEOMORPHIC RESPONSE TO DAM REMOVAL: WISCONSIN AND PENNSYLVANIA EXPERIENCES
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We examined channel adjustments following the removal of dams in Wisconsin and Pennsylvania. Reservoirs in Wisconsin were dominated by silt accumulation, while those in Pennsylvania were dominated by sand and gravel. Channel formation following dam removal in Wisconsin was accomplished through the formation and migration of headcuts, and a predictable sequence of bed erosion and bank widening. Sedimentation downstream of removed dams in Wisconsin was negligible at one site, and temporary at the second site. In Pennsylvania, different geomorphic responses were observed. In the impoundment area, deposition of sand and gravel as alternate and mid-channel bars was the predominant geomorphic response. Downstream, approximately 0.5 m of small gravel was deposited over pebble and cobble sized sediment in riffles. The two studies provide a context for the potential variety of channel response to low-head dam removal. In addition, these studies suggest that current understanding of geomorphic processes can provide at least qualitative predictions of possible channel responses to dam removal.