Designing a Rock Ramp Fishway on Maine's Sedgeunkedunk Stream

In 2008, a dam on Maine’s Sedgeunkedunk Stream was removed and replaced with a rock ramp fishway to restore anadromous alewives to Fields Pond.  The design of the rock ramp fishway had to address many challenges, including the maintenance of a minimum pond elevation upstream to protect wetland habitat and a meandering stream profile.  Other design challenges included the maintenance of acceptable depth and velocities for fish passage throughout a wide range of streamflows, and the stability of rock ramp features such as boulder weirs.  The rock ramp included some elements—such as a concrete core wall and impervious membrane—not typically used in rock ramp design.  The project highlighted the importance of continued monitoring and maintenance of nature-like fishways, and illustrated how the use of natural materials challenges the construction of rock ramp fishways to exact design specifications.  Lessons learned from the design of the rock ramp fishway are being incorporated into an East Coast diadromous fish passage manual prepared by the U.S. Geological Survey and NOAA Restoration Center.