The purpose of this study was to determine the flow conditions in the transitions and curves in the supercritical channel, at the confluences with the Fiske Brook and Tophet Brook Channels, at the drop structures, and in the reach where the flow transitions from supercritical to subcritical flow. Particular attention was directed to evaluating the consequences of the channel changes that have occurred since initial construction. These changes are predominately the deposition of sediment in the lower portion of the modeled reach. The study was primarily for the purpose of evaluating various modifications to the lower end as part of a channel restoration project. The model was to determine if restoration alterations would change water surface elevations associated with the design discharge.
The first phase of the study tested the numerical model's ability to reproduce the hydraulic conditions observed in a previously published physical model study. After the numerical model was validated, the as-built conditions were simulated to establish water-surface elevations associated with the initial design and construction. After as-built flow conditions were established, flow conditions produced with the existing conditions of the channel were computed. The existing conditions include large deposits of sediments at various locations within the channel, so there was a question as to how this may change water-surface elevations during flood events. The final phase of the study was the hydraulic evaluation of restoration alternatives to determine their impacts on water surface elevations. More information can be obtained from ERDC/CHL TR-09-17.