Problems With Dams
As dams age, the most common problems are undesirable woody vegetation on the embankment, deteriorated concrete, inoperable gates, and corroded outlet pipes. Over time, water pressure and weathering will slowly break down a dam. Dams need constant maintenance and repairs. If dams are allowed to naturally degrade, they have a greater risk for problems such as sudden breaks during flood conditions. The possibility for loss of life and property make dam maintenance an important issue. Dams left to deteriorate in place can also pose a threat to the life and health of the public using waterways for swimming and boating.
Environmental Impacts of Dams Include:
- Block or inhibit upstream and downstream fish passage
- Increase water temperatures
- Decrease water oxygen levels
- Obstruct the movement of sediment, woody debris and nutrients
- Inundate wildlife
- Alter timing and variation of river flows
- Block or slow river flows
Dams are built to temporarily slow the flow of water and create an artificial impoundment, or lake, just upstream of the dam. Water held by the dam is often warmer than the natural water temperature and attracts different fish and mammal species. Dams prevent native fish from utilizing different stream segments, which can be important seasonally or during different stages in their life. Naturally flowing rivers are often cleaner and clearer in water quality than water held by a dam, since nutrients and sediment can be naturally discharged in flowing water. Impoundments created by dams sometimes need to be dredged to remove sediment build up behind the dam. Beavers and muskrat are also attracted to dams. They can burrow into embankments and compromise the structure’s integrity, creating public safety concerns.
Benefits of Removing Dams
Dam removals are often a necessity caused by the high cost of dam reconstruction and maintenance. Removing a dam also often removes a hazard to swimmers and boaters in the area and those who live downstream.
Environmental Benefits Include:
- Re-connection of important seasonal fish habitat
- Normalized temperature regimes
- Improved water clarity (in most cases)
- Improved dissolved oxygen concentrations
- Normalized sediment and energy transport
- Improved biological diversity
Recent removals of dams have shown a higher water quality and biodiversity after removal. Overall, dam removal benefits riverine fish by: (1) removing obstructions to upstream and downstream migration; (2) restoring natural riverine habitat; (3) restoring natural seasonal flow variations; (4) eliminating siltation of spawning and feeding habitat above the dam; (5) allowing debris, small rocks and nutrients to pass below the dam, creating healthy habitat; (6) eliminating unnatural temperature variations below the dam; and (7) removing turbines that kill fish.
Dam Removal in Northern Michigan
Dam removal is one of the most important river restoration opportunities of the 21st century. Thousands of old, unsafe and uneconomical small dams across the United States have outlived their usefulness and should be considered for selective removal. Tip of the Mitt Watershed Council has experience with small dam removal in Northern Michigan and supports the promotion of small dam removal as a means of river restoration. Removal of dams allow rivers to become once again healthy, thriving babbling brooks in Northern Michigan improving the water quality in the Great Lakes and promoting a healthy population of native fish.
Tannery Creek Dam
The Watershed Council worked to restore Tannery Creek, the third-largest tributary of Little Traverse Bay, to protect the water quality in the Bay and a healthy population of native brook trout. A large, stone wall and a low head dam were originally constructed to prevent erosion and create a water feature on a golf course. This dam was segmenting the brook trout population of Tannery Creek and had deteriorated to the point where it was posing a serious threat of failure.
The dam removal project, after much careful planning and cooperation, took four days and involved diverting the stream flow around the dam, constructing a new stream bed, and reintroducing flowing water. To address the issue of invasive species, an innovative and cost-effective sea lamprey barrier was designed, built, and installed as part of the restoration. The successful removal of the dam has allowed the Tannery Creek to become once again a healthy, thriving babbling brook in Northern Michigan.
Chandler Dam was a lowhead dam spillway on the upper reaches of the Black River in the Cheboygan River Watershed. This dam was non functional and in disrepair. It’s presence on the river was threatening the unique brook trout fishery of the Upper Black River. During times of low-flow, such as in the summer, lowhead dams degrade fisheries habitat and water quality by restricting fish passage and contribute to thermal pollution by impounding water upstream of the dam. During high-flow periods in the winter and spring the accumulated sediments and organic material upstream of the dam are flushed downstream contributing sediment pollution to the river. Much of the Upper Black River is considered a premiere fishery, unique in that it is home to only one species of trout—the prized brook trout. Removal of the dam restored 9.5 miles of this “Blue Ribbon Trout Stream” for fish passage, as well as restored the natural stream bottom, improved sediment transport, and improved aquatic habitat.
For More Information
Michigan Department of Natural Resources Dam Removal Webpage
Dam Management Grant Program
Michigan Department of Natural Resources Dam Management Grant Program
Map of Hydroelectric Dams in Michigan
(Above data adapted from dam removal information compiled by American Rivers, Trout Unlimited, and Wisconsin Department of Natural Resources.)