Influence of Historical Land-Use Change on Contemporary Channel Processes, Form, and Restoration

Abstract

Big Harris Creek, North Carolina, possesses a geomorphic history similar to many drainages in the southern Appalachian piedmont, and was used herein as a representative example of the influence of European settlement on contemporary channel form and processes. The integrated use of historical, dendrogeomorphic, stratigraphic, and cartographic data shows that the conversion of land-cover from a mix of natural conditions and small farms to commercial cotton production in the late 1800s and early 1900s led to significant upland soil erosion, gully formation, and the deposition of legacy sediments on the valley floor. Aggradation was followed by catchment-wide channel incision in the mid-1900s in response to reforestation and the implementation of soil conservation measures. Collectively, the responses form an aggradational-degradational episode (ADE) that produced the geomorphic framework for the contemporary processes operating along the drainage network. Defined, characterized, and mapped process zones (stream reaches of similar form and process) show that the type, intensity, and evolutionary sequence of geomorphic responses varied within the catchment as a function of the position along the drainage network, the erosional resistance of the underlying bedrock, and the valley characteristics (particularly width). Understanding the spatially variable influences of the ADE on contemporary, reach-scale geomorphic processes provides valuable insights for restoration as it helps inform practitioners of the sensitivity and ways in which the reach is likely to respond to future disturbances, the potential impacts of processes on proposed manipulations intended to achieve the project’s restoration goals, and the potential risk(s) involved with channel reconstruction. The latter is strongly controlled by geotechnical differences between erosionally resistant precolonial deposits and easily eroded legacy sediments that locally form the channel banks following the ADE.