Stream restoration design using sediment transport modeling and risk assessment

To achieve a successful stream restoration, it is helpful to understand the relationships between channel form and processes, the effect of infrastructure and hard points on channel processes, current and future stream channel conditions, and the uncertainty involved with project design and implementation. Field investigations and long-term alluvial channel modeling were used on a relocation design case study reach to evaluate the effect of rigid in-stream structures on channel processes and verify the current and future stream channel stability. Results were used to identify instances where rigid in-stream structures have a significant impact on channel form and adjustment. Though the use of stability verification methods, changes to initial design characteristics that would have resulted in a more stable, sustainable project are also presented. The use of sediment transport stability verification design alternatives, can involve considerable upfront time and effort; however, application can result in modifications that reduce project uncertainty, and risk. A risk based design approach using Design Failure Modes and Effects Analysis and risk quantification is an efficient means to include uncertainty and decision-making in design. The estimates of risk for several design alternatives for a case study reach are compared to provide justification for selecting a cost effective restoration design. Copyright ASCE 2005.