Corydon Dam Removal

Project Summary

With a growing push to remove low-head dams due to safety concerns and the potential for ecosystem improvement, Corydon, Indiana was approached by The Nature Conservancy to remove two dams owned by the Town. The dams blocked potential habitat for the endangered hellbender salamander, so funding was available from a variety of sources, allowing Corydon to remove their dams at no cost to the Town. Now that the dams have been removed, Corydon has less liability and the health of the river ecosystem can begin to improve.

Two low-head dams in the 1960s were built by Corydon in Big Indian Creek for water storage purposes. The Town’s water supply is no longer Big Indian Creek and the dams were not used for flood control purposes. Low-head dams are notoriously dangerous to people using the waterways for recreation. Several drownings have occurred at one of the dams in recent years. The Town of Corydon owned these dams, and liability was a concern.

Dams also alter fish migration, fragment important ecological functions of stream, and may negatively affect water quality. Big Indian Creek has been evaluated as habitat potentially suitable for hellbender salamanders, an endangered species in Indiana. Currently, in Indiana, hellbenders are only found in the Blue River. Big Indian Creek has been identified as a historical habitat of the hellbender with similar natural qualities as the Blue River. However, the presence of dams has altered the habitat in a way that prevented hellbender migration within the stream. Dams are a barrier that isolates hellbenders and present other negative changes in a river such as lower dissolved oxygen in the artificial pools created behind dams.

In June 2017, the Town of Corydon was approached by The Nature Conservancy. The Corydon Town Council was apprehensive about removing the dams at first due to cost and concerns over increased flooding, so representatives from the Town of Corydon and The Nature Conservancy met with the Indiana Department of Natural Resources and the US Fish and Wildlife Service. Their discussion focused on how dam removal would work and the potential costs and benefits for the Town. This in-person meeting was important as it established a level of trust and allowed for a better flow of information from the researchers to the Town Council.

The Corydon Town Council wanted to know if removing the dams would lead to flooding, so a US Fish and Wildlife Service hydrologist ran a model based on flood insurance maps. The model showed that the dams were not actually controlling flooding, so their removal would not create future flooding issues. If anything, the removal might actually reduce flooding upstream of the dams by a small amount. The removal would also allow for more water flow downstream to Corydon where the streambed often gets low in the summer and has little flow. As more sediment flows in with the additional water, algae on the gravel will be reduced and aquatic plants will be more likely to root, which can reduce erosion and stabilize banks.

The Nature Conservancy presented these findings to the Town Council. The Council then gave approval to begin seeking funds to remove the dams and said they would approve the project once sufficient funding was identified.

The Town of Corydon and The Nature Conservancy began to look into the specifications of the dam and what options were available for removal. They found Ecosystems Connections Institute who had done work on dam removals in the Eel River in northcentral Indiana. Ecosystems Connections Institute navigated the logistics of dam removal and handled the permitting process through the Indiana Departments of Environmental Management, Natural Resources, and State Historic Preservation as well as the US Army Corps of Engineers.

The Nature Conservancy identified grant opportunities. They found the Indiana Department of Natural Resources’ Lake and River Enhancement Program and the National Fish Passage Program through the US Fish and Wildlife Service. The Nature Conservancy and Ecosystems Connections worked with Corydon to write the grants, which were submitted in December 2017. They received notice in January 2018 of the awards for the removal. Some of this funding was available to Corydon because of the potential hellbender habitat.

Beginning in August 2018, Ecosystems Connections Institute began sampling the health of the river and the fish present. They discovered that the area furthest upstream, the pool with the largest area, had the lowest levels of fish. They also determined that wildlife was the healthiest after a third dam further down the river, so removing the two upstream dams would provide the best impact to the ecosystem.

Ecosystems Connections Institute managed the permitting process throughout the project. Permitting can be an impediment to dam removal as the process is cumbersome and not clear-cut as it deals with multiple agencies and people. Working with partners who have gone through the process simplified the project for Corydon. All permits were acquired by July 2019.

In partnership with Ecosystems Connections Institute and The Nature Conservancy, the Town hosted a public meeting in May 2019 to inform residents of the plans for and purpose of dam removal, and to gather feedback from the community. During the meeting, there was little dissent from residents. Likely factors in the low amount of dissent were Corydon not having to pay out-of-pocket because of the grants, habitat restoration, public safety improvement, and the dams not being prominent features people saw on a day-to-day basis.

All relevant parties had approved the dam removal project by the summer of 2019. The project was scheduled for the fall when the creek would be in a lower water stage. The dam removals took place in October 2019 and took around two weeks to complete removal. A contractor was hired to do the actual removal with supervision from Ecosystems Connections Institute.

Funding

The total cost of the removals was $304,000. $95,000 was provided by the Indiana Department of Natural Resources Lake and River Enhancement program. The remainder came from the US Fish and Wildlife’s Fish Passageway Program with matching funds from The Nature Conservancy. There was no financial cost to Corydon.

Timeline

Corydon was approached in June of 2017 by The Nature Conservancy and the dams were removed in October 2019.