CHARACTERIZING STREAM EQUILIBRIUM IN WEST-CENTRAL OHIO: A CASE FOR PASSIVE STREAM RESTORATION AND MANAGEMENT

The purpose of this study was to evaluate recent changes in channel morphology, hydrology, and channel and floodplain stratigraphy of Beaver Creek, a tributary stream of the Mad River in west-central Ohio, in an attempt to determine if changes along the reach, primarily excessive bank erosion and moderate incision, indicated a shift away from or towards equilibrium. We evaluated equilibrium based on relations between discharge and channel and pattern characteristics, relative stability of the floodplain and its flood frequency, and hydrology and sediment transport potential of the bankfull condition using a combination of field methods and map and photo analysis using GIS. Beaver Creek is an underfit stream within a glacial outwash valley draining west from the Scioto lobe of the late Wisconsinan ice margin and is underlain by valley train deposits. In the study reach, it is incised 0-2 meters in glacial till. Former channel positions were delineated from aerial photographs of the study area over the period 1938 to 2002. General channel and pattern changes observed included decreased width, from 30 to 10-15 m during the period, increased sinuosity, and increased rate of meander swing and sweep. Changes in sinuosity, radius of curvature, and meander length between 1938 and 2002 indicate the stream is been moving toward a state of equilibrium along some meanders. The physiographic floodplain is no longer accessible by more frequent flood events (< 5 yr RI) as indicated by landowner observations, soil development on the floodplain, and bankfull approximations of discharge relative to measured annual flood peaks. These changes in channel and pattern morphology and hydrology suggest Beaver Creek is responding to decreased water and sediment yield from the watershed. Reforestation of the riparian corridor, probably due to agricultural early set-aside programs and more recent conservation incentives as well as land use change to rural, low-density residential use, may result in less active land management to the stream’s edge and in-stream channel management. If true, this study has important implications for passive stream restoration and capital outlays for improving quality of stream and riparian habitat.