Scheduling Maintenance Dredging on Single Reach with Uncertainty

Abstract

New methods are suggested for scheduling advance maintenance dredging on isolated reaches of navigation channels based on economic and reliability analysis. For reaches where sedimentation occurs regularly as a result of gradual slumping, quiescent deposition, or regular erosion due to waves and wakes, the problem reduces to a deterministic least-cost replacement problem. Where sedimentation rates are uncertain, the risk of sediment encroachment into the navigational channel becomes a concern. Where sedimentation rates are probabilistic and independently distributed in time, encroachment probabilities and expected dredging costs can be calculated for a variety of dredging schedules. This risk and cost analysis allows explicit specification of risk-cost trade-offs in dredge scheduling. These methods are applied to an example case where existing dredging costs are compared with those estimated using these new dredge scheduling techniques. Extensions of these methods could be applied to multiple-reach dredge scheduling, sizing sediment traps, and scheduling dredging with explicit consideration of environmental impacts.