Improvement of overtopping risk evaluations using probabilistic concepts for existing dams

Hyun Han Kwon, Young Il Moon

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


Hydrologic risk analysis for dam safety relies on a series of probabilistic analyses of rainfall-runoff and flow routing models, and their associated inputs. This is a complex problem in that the probability distributions of multiple independent and derived random variables need to be estimated in order to evaluate the probability of dam overtopping. Typically, parametric density estimation methods have been applied in this setting, and the exhaustive Monte Carlo simulation (MCS) of models is used to derive some of the distributions. Often, the distributions used to model some of the random variables are inappropriate relative to the expected behaviour of these variables, and as a result, simulations of the system can lead to unrealistic values of extreme rainfall or water surface levels and hence of the probability of dam overtopping. In this paper, three major innovations are introduced to address this situation. The first is the use of nonparametric probability density estimation methods for selected variables, the second is the use of Latin Hypercube sampling to improve the efficiency of MCS driven by the multiple random variables, and the third is the use of Bootstrap resampling to determine initial water surface level. An application to the Soyang Dam in South Korea illustrates how the traditional parametric approach can lead to potentially unrealistic estimates of dam safety, while the proposed approach provides rather reasonable estimates and an assessment of their sensitivity to key parameters.

Original languageEnglish
Pages (from-to)223-237
Number of pages15
JournalStochastic Environmental Research and Risk Assessment
Issue number4
StatePublished - May 2006


  • Bootstrap
  • Dam safety
  • Latin hypercube sampling
  • Nonparametric Monte Carlo simulation
  • Overtopping probability


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