Removal of Three Barriers to Restore Diadromous Fish Passage on the Pawcatuck River, Rhode Island

The Pawcatuck River is a 300-mi² Southern New England watershed, which historically provided significant spawning and rearing habitat for diadromous fishes.  The presence of 8 mainstem dams and 20 tributary obstructions has contributed to the decline of American shad (Alosa sapidissima), river herring (Alosa pseudoharengus, Alosa aestivalis), and American eel (Anguilla rostrata) in this system.  A NOAA 2009 American Recovery and Reinvestment Act funding award ($2.5+M) targeted restoring effective passage at the three remaining significant mainstem barriers.  Passage restoration types include: (1) dam removal and installation of nature-like weirs, (2) construction of a Denil fishway and eel pass, and (3) construction of a nature-like rock ramp to address site and social challenges associated with each barrier.  Completion of these three projects opens 21 river miles to migratory fish passage and access to 1,043+ acres of high quality spawning and nursery habitat in Wordens Pond, Rhode Island’s largest freshwater lake.  This presentation will summarize the fish passage flows and technical and social challenges affecting fishway design and construction at each site.  The presentation will also focus on federal interagency design criteria for passage dimensions and hydraulics applied in the nature-like fishways, and diagnostic field assessment of the Lower Shannock Falls site in 2011 which led to backwater weir modifications in 2012.