A landslide risk assessment and management considering time effect is proposed. From a statistical point of view

a time-dependent reliability approach for deteriorating slopes is formulated based on about 20-year observed performance of 16 000 soil cut slopes in Hong Kong. The annual probability of failure for new slopes is deduced; and an approach is presented to predict the annual probability of failure for existing slopes within next service time. Risk acceptance criteria in terms of annual risk of fatality are selected. Based on them

a risk based maintenance planning for slopes is obtained. The results indicate that the landslide risk assessment and management considering time effect can be capable of capturing the deteriorating characteristics of slopes effectively. The annual probability of failure for new slopes increases with time. It increases significantly when the service time of slope is longer than a decade. The relationship between the annual probability of failure for existing slopes and service time is approximately linear. In addition

the maintenance planning used in Geoguide 5 can reduce the risk of slope failure to the ALAPR region or the acceptable region effectively.