Probabilistic design of sea defences

Designs of dikes and dunes according to current Dutch guidelines, based on a deterministic approach, are not consistent with probabilistic philosophy. This statement is amplified in the present paper as a pilot investigation; a rough outline for a probabilistic method of dune and dike computation is given. Numerical comparison of probabilistic and deterministic methods is hampered due to the fact that the results according to the deterministic approach depend on engineering instincts in the choice of boundary conditions and because the probabilistic approach is not as yet operational. Illustrative computations show differences of a factor 1000 in failure probability, starting from dimensioning according to the same standards, following deterministic guidelines.