Abstract: To study the impact of landslide dam break floods on the risk of a downstream reservoir, a Bayesian network method and Monte Carlo simulations are used to calculate the conditional probability of reservoir dam break under the combined action of natural floods and landslide dam break floods, and the risk of reservoir dam break is evaluated. A case study of the Houziyan reservoir shows that at its normal water stage, the conditional probability of dam break caused only by natural floods is low or the risk is low, while the one caused only by landslide dam break floods is greater than 0.3. And the risk is increased by tens of thousands of times under the combined action of two types of floods.

Key words: natural flood, landslide dam, probability of dam break, Bayesian network, Monte Carlo simulation