UNDERGRADUATE COURSE FLUME EXPERIMENTS TO DEVELOP PHYSICAL MODELS USEFUL FOR INTERPRETING FIELD STUDIES OF FLUVIAL PROCESS AND CHANNEL EVOLUTION IN RESPONSE TO CLIMATE AND LAND USE CHANGE IN THE SUSQUEHANNA WATERSHED

Field studies in the West Branch Susquehanna River (WBSR) over the past decade have shown that fluvial morphology has been significantly influenced by the legacy of deforestation and Pleistocene breakout floods. The Applied Environmental Geomormophology (GEOL 310 Spring 2014) course at Bucknell University required students to conduct independent team-based field and laboratory research. A 12m x 2.4m tilting, sediment recirculating flume was used to test conceptual models of channel processes and evolution. Flume studies allow students to investigate fluvial response over a variety of scales to changes in variables such as discharge, sediment load, and gradient. Design of the flume experiments were based on historical documentation, dendrogeomorphic dating of logging legacy sediments, flood geomorphic studies, bathymetric/geomorphic mapping of the WBSR valley and channel, and a HEC-RAS model of paleofloods.

The first project focused on channel response in tributaries resulting from changes in sediment load as a consequence of basin-wide deforestation, followed by historic floods. The logging study also included anthropogenic physical changes in the channel such as straightening and berming. This study concluded with a phase of clear water flow simulating reforestation of the watershed. The second project used concrete to represent a bedrock paleochannel and a sediment dam to simulate glacial outburst floods and the evolution of large-scale bedforms and sedimentology in WBSR. This experiment resulted in the formation of islands, terraces, and slackwater deposits known from field studies. Students learned how to plan research projects, organize as teams, design flume experiments, collect and map the geomorphic changes in detail using a laser mapping system, analyze changes over time, and relate their flume observations to field observations. The flume projects proved to be valuable teaching tools for students to visualize channel adjustments to land use, flooding, and large-scale climate change. These studies demonstrated direct linkages between quantitative geomorphic changes in the flume and field observations. With dimensional analysis and scaling, these studies could be extended to develop predictive physical models.