Optimal Plans and Costs for Maintenance Dredging Operations

An adaptation of the classical inventory system model of operations research is suggested for planning and scheduling maintenance dredging operations in navigation channels. In the sediment inventory model (SIM) that results, the costs of periodic and advance maintenance dredging are set against the economic and safety implications of sediment encroachment into the channel. Among SIM variations, the situation when sediment rates are constant and dredging costs reasonable to predict, optimal dredging plans, costs and schedules may be determined by mathematical techniques such as differential calculus. Properly formulated, the resulting SIM models yield least-cost solutions and also reveal optimal relations between competing costs and alternative criteria such as safety and navigation efficiencies. When sediment rates are probabilistic and dredging costs uncertain, the stochastic SIM variant may provide useful insights into appropriate dredging policies and risks of encroachment. Through examples, this paper illustrates the results of the basic SIM variants as they apply to maintenance dredging, and suggests extensions and limitations of the model to such complexities as lead-time scheduling of dredging equipment.