Low-head dam removal in Muncie, Indiana: geomorphological substrate change and local fish community response

Abstract

Dams impair riverine ecosystems through multiple documented environmental and ecological problems. Due to this recognition dams worldwide have begun to be removed. In recent years, progression of river restoration programs focused on dam removal has surfaced. However, few studies have quantified substrate change and its impact on local fish communities following dam removal. The purpose of this study was to assess changes in 1) substrate geomorphology and 2) fish communities associated with the 2019 removal of two low-head dams, East Jackson St. dam and McCulloch Park dam, on the West Fork, White River in Muncie, Indiana. Side-scan-sonar was used to map substrates in 2012, 2017, and 2021. Using ArcGIS software, specific substrate types were delineated, and substrate areas were quantified. Fish communities were sampled annually from 2018 to 2021 at sites directly above and below the two low-head dams, in accordance with Muncie Sanitary District’s Bureau of Water Quality annual sampling practices, using standardized electrofishing methods. Major variation occurred in the dominant substrate type and structure of the fish community structure following dam removal. At both dam sites, bedrock substrate increased over other substrate categories, while unidentified substrate had the greatest decreased rate of change, followed closely by sand substrate. Fish species richness shifted from the highest richness below dams prior to dam removal, to highest richness above dams following dam removal. Dominant fish taxa changed following dam removal. These results support continued monitoring and understanding of long-term effects associated with dam removal on the White River, and the use of dam removals as a river restoration tool elsewhere.