Sediment Modeling to Develop a Deposition Prediction Model at the Olmsted Locks and Dam Area

The present study focuses on the sediment deposition and consequent dredging issues in Lower Ohio River at the Olmsted Locks and Dam area-river mile (RM)-964.4 during the ongoing in-the-wet construction methodology. The study reach is between locks & dam 53 (RM 962.6) at upstream, and RM 970 at downstream. One dimensional (1D) HEC-RAS numerical modeling in conjunction with Arc-GIS was employed. Streamflow measurements, velocity, incoming sediment concentration, bed gradation, and annual hydrographic survey data acquired from public archives of USGS and USACE Louisville District were used as inputs. The first model applied was the 1D quasi-unsteady HEC-RAS module. Calibration and validation of the hydrodynamic and sediment models were performed using measured water surface elevation, velocity, and sediment loads at measured sections. Post-model calibration and validation, deposition to excavated cross-sections for future dam shells at Olmsted were predicted, validating the need for dredging. Sensitivity analysis for transport capacity functions provided the basis of model validation. Moreover, the capability of 1D-HEC-RAS quasi-unsteady model was assessed in prediction of sediment accumulation in the construction area (dam shells excavation area). A temporal deposition prediction model was developed that could potentially replace the current ad-hoc approach used to determine the dredging schedule. A representative environmental risk associated with sedimentation in the study area was examined. This model could potentially be used as a decision support tool to analyze the long term impact of sedimentation in the vicinity of Olmsted locks and dam if further updates on the river bathymetry and specific field data are supplemented to the model.