Frankenmuth celebrates a fish passage success story

Rock ramp revitalizes river habitat and downtown aesthetics.

Ribbon cutting celebrating the completion of the Frankenmuth rock ramp project. Photo credit: The Conservation Fund

Ribbon cutting celebrating the completion of the Frankenmuth rock ramp project. Photo credit: The Conservation Fund

There are more than 300 dams in the Saginaw Bay watershed. These structures were originally built for a variety of purposes including timber transportation, hydroelectric power generation, and flood management. Over the years dams have had a host of secondary impacts on river habitat in the watershed and on Great Lakes fisheries. Dams impede fish migration limiting access to the river tributaries where many Great Lakes fish species spawn. Dams also fundamentally change river habitat conditions impacting the volume, temperature, depth, and velocity of water at different points in the river. Dams can even influence dissolved oxygen levels and sediment loads.

Over the past century, as scientists have come to better understand the full impacts of dams on the environment, dam infrastructure has also aged. Today communities across the Saginaw Bay watershed and Michigan struggle with high maintenance and repair costs on dams that in many cases no longer serve their original purpose. However, removing dams entirely can be expensive and communities often have concerns about altering the river profile that landowners and recreational users have grown accustomed to. The potential impact of dam removal on invasive species proliferation is also a concern. Some aquatic invasive species like sea lamprey are prevented from spreading upstream by dams. It is important for any fish passage project to include provisions to prevent invasive species from expanding into new habitat.

While the debate surrounding dams in Michigan is complicated, many communities are finding creative ways to improve fish passage and habitat while also minimizing the potential disadvantages of dam removal. Recently the City of Frankenmuth celebrated the completion of a new rock ramp that opened up more than 73 miles of historic spawning habitat to Saginaw Bay fish species.

A rock ramp is just one method used to help fish breach the barrier of a dam without significantly altering a river’s profile. A rock ramp is essentially a series of manmade rapids leading up to a dam from river level allowing fish to move over the dam without significantly changing water levels upstream (imagine being able to climb a staircase rather than trying to jump over a wall). The end result is significant habitat improvement for a variety of fish species as well as new recreational opportunities for anglers and kayakers. The Frankenmuth rock ramp was officially completed in the fall of 2015 and provides a real success story of several regional collaborators coming together to solve the problem of an aging dam.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

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