Quantitative Vulnerability Model of Earth Dam Overtopping and its Application

Dam failure constituted a considerable threat to human life and created corresponding losses. Hence, this paper proposed a quantitative vulnerability evaluation model to estimate the consequences of dam overtopping, including loss assessment and vulnerability degree calculations. A composite normalized function was applied to convert dam overtopping loss to a vulnerability degree ranging from 0 to 1. In addition, many complex factors were simplified in the loss estimation, and the thresholds of various types of losses were proposed and adapted to the national and regional conditions. Then, loss of life, economic loss, social loss and environmental loss were incorporated into the vulnerability degree model based on a comprehensive evaluation method and were further assigned weights. Finally, vulnerability degree grading criteria was divided based on three significant cut-off values, and the corresponding guidelines for vulnerability evaluation were explained in detail. The methodology was applied to Chengbihe Reservoir in China to illustrate the assessment process of flood overtopping loss and to evaluate the vulnerability degree of the area. The results indicated that (1) dam overtopping vulnerability degree of the Chengbihe Reservoir was 0.89, which was within the range of “extremely high vulnerability” and (2) countermeasures were necessary; for example, early flood warning and forecast systems must be developed for the reservoir so that people and property in flooded areas can be safely evacuated during the process of emergencies.