Case History of Risk Evaluation of Earth-Fill Dams Due to Heavy Rain

The present paper describes an assessment method for risks brought on by heavy rain in order to determine the priority of countermeasures for small earth-fill dams. To evaluate the failure risks of an earth-fill dam, defined as the product of failure probability and damage costs, an unsaturated seepage flow analysis is carried out based on the measured rainfall conditions. The damage costs are calculated using the correlation between the results of a flood analysis after breaching and land use and asset data. Subsequently, an evaluation to prioritize the countermeasures is conducted based on the failure risks. The larger of the two comparative failure probabilities—namely, the probability of overflow and the probability of slip failure—will showcase the dominant factor in the failure of small earth-fill dams, and the failure risk evaluation will determine the priority of the countermeasures for repairing and/or reinforcing decrepit earth-fill dams.