To protect the Dutch polders against flooding, more than
2500 km of dikes have been constructed. Due to settlement,
subsoil consolidation, and relative sea-level rise, these
dikes slowly sink “away into the sea” and should
therefore be heightened regularly (at present, every 50
years). In this respect, one is interested in safe and
cost-optimal dike heightenings for which the sum of the
initial cost of investment and the future (discounted)
cost of maintenance is minimal.
For optimization purposes, a maintenance model has been
developed for dikes subject to uncertain crest-level decline.
On the basis of engineering knowledge, crest-level decline
has been modeled as a monotone stochastic process with
expected decline being either linear or nonlinear (i.e.,
linear after transformation) in time. For both models and
for a particular unit time, the increments are distributed
according to mixtures of exponentials.
In a case study, the maintenance decision model has been
applied to the problem of heightening the Dutch