Evaluation of Parametric Breach Models from Prototype and Historical Embankment Dams under Overtopping Conditions

Abstract

The primary cause of embankment dam failure is the overtopping of the crest, making dam safety a crucial consideration due to the potential for catastrophic consequences. Dam safety regulations and guidelines are increasingly demanding the enhancement of rockfill dams’ resistance to overtopping and leakages. Assessing the breaching of embankments is essential for conducting risk evaluations and hazard studies. Typically, this assessment is carried out using parametric breach models, which are statistically derived equations based on historical dam failure cases. However, these models often overlook important parameters such as material properties, leading to uncertainties in the results. This research focuses on quantifying the accuracy of breach parameters (breach width, failure time, peak outflow) predicted by various parametric breach models found in the literature. Three prototype embankment dams (homogeneous earthfill dam, homogeneous rockfill dam, and zoned rockfill dam), along with five historical failure cases, are considered to evaluate the predictive capability of the parametric breach models. The study compares the measured and estimated breaching parameter values, aiming to identify the most suitable parametric breach model based on the dam design. The results indicate that the performance of the different equations in estimating breach parameters significantly depends on the characteristics of the dam and reservoir. Additionally, a simplified physical model (DLBreach) is employed to estimate breach parameters for the three prototype dams, and a comparison with results from parametric breach models is presented. In conclusion, accurately predicting breach parameters is vital for improving dam safety. This research highlights the influence of dam and reservoir characteristics on the performance of different parametric breach models. By identifying the most suitable breach models for specific dam designs, this study contributes to the understanding and management of embankment dam failures.