Development, Validation, and Application of a Two-Dimensional Sediment Transport Model of the North Fork Toutle River, Mount St. Helens Fish Collection Facility

Adaptive hydraulics (AdH) and its sediment transport library were utilized to support the USACE Portland District’s evaluation of the Mount St. Helens Fish Collection Facility (MSH-FCF) modifications. These potential modifications consisted of a modified geometry of the facility, updated design flow withdrawals, and upstream river training structures. Numerical moveable bed models were developed of both the prototype and the 1:12 physical model that was also utilized to support the evaluation of alternatives. The scale physical model provided a more controlled system and ample data resulting in a unique opportunity for the AdH model validation, which this paper focuses on. Overall, the AdH model was able to accurately replicate geomorphic trends that occurred in the physical model, providing confidence in using the model to evaluate alternatives. The model results support the idea that the proposed alternatives can help to reduce the detrimental shoaling issues in front of the intake but do not reduce the sediment loading into the intake; therefore, indicating that additional measures to handle the sediment are needed within the facility.