Dam Removal Boosts River’s

Water Quality and Fish Passage

Removing the Nashville Dam on the Thornapple River in Southwest Michigan has improved fish habitat and water quality, increased fish diversity, and provided more recreational opportunities.

Description

By the 21st century, the Nashville Dam, originally built in 1854 to provide power for a sawmill, no longer served any functional purpose. In fact, the dam blocked fish passage in the Thornapple River and trapped sediment behind it, leading to low oxygen levels in the river. Appropriate levels of oxygen in the water is essential for the health of all fish and aquatic organisms—just like oxygen is necessary for people to live. Low oxygen levels can lead to fish kills.

Removing the dam improved oxygen levels in the river and helped open up 60 miles of unimpeded fish passage and a further 105 tributary miles. The project also helped reconnect five inland lakes to the river system. The associated millpond was drained, leaving approximately 60 acres of new floodplain. Following the removal of the Nashville Dam, the Barry Conservation District and partners worked with many landowners along the floodplain area to install native plants and to enhance habitat by constructing shallow wetland areas.

Resource Challenges Addressed

  • Low dissolved oxygen
  • Fish die-off
  • Barrier to fish passage
  • Aging and hazardous structure
  • Poor aquatic population rates above the dam
  • Heavy sediment build up behind the dam
  • Limited recreation capacity

NASHVILLE DAM REMOVAL AND FLOODPLAIN RESTORATION

The Thornapple River with large boulders replacing the removed dam

The Thornapple River with the Nashville Dam removed. The large boulders in the river provide habitat for a variety of fish and aquatic wildlife. Photo credit: U.S. Fish and Wildlife Service.

Results and Accomplishments

Removing the Nashville Dam provided more than 60 miles of river access to fish and improved Thornapple River’s water quality. Fish such as bass, northern pike, and walleye are returning, providing new fishing opportunities for the public. A survey done two years after the dam removal confirmed that species diversity and abundance had increased. Recreation on the river is improving annually, with more canoe and kayak traffic and improved fishing opportunities above the former dam. The former millpond now provides approximately 60 acres of wildlife habitat along the river corridor, attracting waterfowl, seasonal nesting birds and mammals. The diversity of aquatic wildlife in general has also improved.