USING RELATIVE ELEVATION MODELS TO INFORM STREAM RESTORATION PROJECT DESIGN IN THE MIDWEST

In the U.S., stream restoration projects aimed at reestablishing stream function are a billion-dollar industry. However, rarely is the geologic record utilized to help inform stream restoration project design. Recent geological studies in the mid-Atlantic region of the 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? If so, to which form should we restore streams? GIS analysis using a relatively new technique called a Relative Elevation Model (REM) can provide a greater understanding of stream planform prior to European settlement, inform surficial geologic field mapping, and help determine the location of channel migration zones in stream restoration project designs.

Here we report on the initial results of a research project aimed at reconstructing the pre-European settlement stream planform of an 18-km stretch of Four Mile Creek in southwestern Ohio. For the first phase of our research we used new high-resolution LiDAR data to create a REM basemap in ArcGIS. A REM is a technique that is similar to a Digital Elevation Model, but it displays elevation relative to river water level. By eliminating the downstream gradient change, the REM provided clearer visualizations of terraces and past channels in our study area. In this study, we compared different REM methodologies to determine the outcome quality and time-commitment associated with each method. We then compared the REM of our study area with REMs of minimally disturbed reference watersheds of anabranching and meandering streams. We were able to determine which planform our study area most matched, as well as variations in planform spatially throughout the study area. Additionally, the REM provided insights into different mapping units for surficial field mapping.