RECONSTRUCTING STREAM MORPHOLOGY AND PLANFORM PRIOR TO EUROPEAN SETTLEMENT, FOUR MILE CREEK, SOUTHWESTERN OHIO

Over the past several hundred years, streams in the U.S. have been significantly and rapidly altered due to the effects of widespread land-use changes and channel modifications. Stream restoration projects aimed at reestablishing stream function are a billion-dollar industry – making project success both financially and ecologically important. But to what form should a stream be restored? Recent studies in the eastern U.S. have proposed that impacts associated with European settlement altered channel planform from anabranching (vegetated multi-thread) to meandering (single-thread). Is this also the case in the Midwest? Here I report on the results of a research project aimed at reconstructing the stream morphology and planform of an 18-km stretch of Four Mile Creek in southwestern Ohio prior to European settlement.

A Relative Elevation Model (REM) was created from high-resolution LiDAR data to identify fluvial terraces and past channels within the Four Mile Creek floodplain. Then, based on the REM, two transects were selected where multi-thread channels may have been preserved in the geologic record. We then excavated trenches along these transects to help determine whether these channels were meandering or anabranching and collected samples for radiocarbon dating. Abundant meander scars seen in aerial imagery as well as the presence of clear lateral accretion surfaces within the channel deposits of one of the excavated trenches indicate a meandering system was present during the early Holocene. Another transect of trenches exposed two contemporaneous (anabranching) channels with radiocarbon ages of ~1,500 cal yr BP that had incised into a unit of ~4,500 cal yr BP channel deposits. The presence of anabranching channels during the late Holocene, prior to European settlement, suggests a more dynamic fluvial system alternating from meandering to anabranching planform over time. The end results of this study will help inform stream restoration efforts in the Midwest by providing a baseline understanding of stream planform prior to European settlement.