OPTIMAL MAINTENANCE DECISIONS FOR BERM BREAKWATERS

To prevent coastal lines of defence from being affected by severe hydr aulic loads from the sea, berm breakwaters can be used. Although berm breakwaters are dynamically stable in the sense that they allow for so me rock displacement, they can fail due to severe longshore rock trans port. To avoid this type of failure, berm breakwaters have to be inspe cted and, if necessary, have to be repaired. A decision model is prese nted enabling cost-optimal maintenance decisions to be determined whil e taking account of the (possibly large) uncertainties in: (i) the lim iting average rate of occurrence of breaches in the armour layer and ( ii) given a breach has occurred, the limiting average rate of longshor e rock transport. The stochastic process of rock displacement is model led by a modified generalised gamma process, enabling the uncertainty in these limiting averages to be explicitly taken into account. Copyri ght (C) 1996 Elsevier Science Ltd