Optimal maintenance decisions for berm breakwaters

To prevent coastal lines of defence from being affected by severe hydraulic loads from the sea, berm breakwaters can be used. Although berm breakwaters are dynamically stable in the sense that they allow for some rock displacement, they can fail due to severe longshore rock transport. To avoid this type of failure, berm breakwaters have to be inspected and, if necessary, have to be repaired. A decision model is presented enabling cost-optimal maintenance decisions to be determined while taking account of the (possibly large) uncertainties in: (i) the limiting average rate of occurrence of breaches in the armour layer and (ii) given a breach has occurred, the limiting average rate of longshore rock transport. The stochastic process of rock displacement is modelled by a modified generalised gamma process, enabling the uncertainty in these limiting averages to be explicitly taken into account. Copyright (C) 1996 Elsevier Science Ltd