Optimal risk-based inspection and dredging scheduling for independent dredge reaches

Channel maintenance dredging is a significant investment, and techniques to improve the decision process are needed. A methodology for determining the least cost schedule for inspecting and dredging a single channel reach is presented in this paper. The methodology determines a control-limit rule, which minimizes the expected cost of maintaining the reach. The approach accounts for the uncertainties in the shoaling rate and in the streamflow. All applicable costs are included in determining the best policy, including the unit dredging cost, mobilization and demobilization cost, and the expected failure cost. A fast-solution algorithm using a policy-iteration scheme allows a range of conditions and sensitivities to be analyzed. The model will be useful for comparison with present maintenance strategies and for examining the potential of advanced maintenance dredging. An application example is shown to demonstrate the model, its results, and costs, which may significantly affect the decision process.