MULTIPLE MODEL ANALYSIS OF SEDIMENT TRANSPORT AND CONTAMINANT DISTRIBUTION IN THE CLINCH RIVER WATTS BAR RESERVOIR, TENNESSEE, USA

Three models of sediment transport and contaminant distribution (CHARI MA, HEC-6, and TODAM) are being applied to the Clinch River/Watts Bar Reservoir system as part of a CERCLA remedial investigation. Planned u ses of model results are to identify high deposition areas of the rive r, forecast the effects of various remedial actions and climatic event s on contaminant distribution, and aid in the design of future data co llection efforts. The three models share some similarities but also di ffer in several important details. All three models are one-dimensiona l and include similar processes for sediment deposition and resuspensi on. Differences among the models include steady-state versus unsteady flow, the complexity of the channel network permitted, and the level o f detail of contaminant-related fate processes represented. As part of our multiple model strategy, some aspects of the three models are con figured using common information on the system (e.g., spatial geometry ), while other aspects of the models, including some modeler decisions and calibration methods, are allowed to differ. Comparison of results among the three models can lead to increased confidence in prediction s and in recommendations for future data collection. The general appro ach of using multiple models is described and preliminary results of t he Clinch River/Watts Bar application are presented to illustrate the utility of using a multiple model approach for complex environmental a ssessments.