THE IMPACT OF MILL DAMS ON STREAMS IN SOUTHWESTERN OHIO

Prior to the early 20^thCentury, mills and mill dams were common features on streams in the eastern United States as water was the main source of power for grinding grain, sawing lumber, and many other industrial applications. Recent studies in the mid-Atlantic region of the US have proposed that mill dams had a profound impact on streams through the trapping of sediments and altering of channel morphology from anabranching to meandering. This research challenged stream restoration projects that assumed that meandering streams were the natural system. Here we assess the impact of four long-standing (>50 years) mills on streams in southwestern Ohio.

The first phase of this research was to use historical atlases and LiDAR data to identify the location of the mill races and therefore pinpoint the locality of the mill dams. Once the location of the dams were determined, we assessed the potential trapping of historic sediments upstream from the dam using ArcGIS and through examination of outcrops in the field. We failed to identify any evidence of historic sediments trapped upstream from the original dam locations. Our initial assessment is that streams were incising in southwestern Ohio during the late 19^th Century. Therefore, these systems were not conducive to the trapping of sediments behind dams that were likely quite ephemeral and blown out by large floods every few years. Additionally, abundant meander scars in Holocene floodplains suggest that streams in southwestern Ohio were, and continue to be, meandering systems.