Experimental Investigation and Application of Soft Computing in the Assessment of Breach and Outflow Hydrograph in the Embankment Dam Break

Determination of the breach parameters and resulting hydrograph of the embankment dam failure due to overtopping and piping erosion has great importance because of the significant injuries and environmental impacts. In this research, by investigations on the erosion mechanisms, the affecting processes on the embankment dam failure are examined, and empirical relationships are presented to determine the peak outflow discharge (Qp), time, and breach characteristics in the overtopping and piping failure cases. Physical models with different heights and technical specifications were constructed and failed in the experimental flume to study the breach expansion rates. In the other part of the research, new empirical relations have been developed to predict the eroded volume (Ver) based on the breach characteristics and the contribution of various resources including historical, experimental, and hypothetical failures of the real embankments. The BREACH mathematical model has been used to obtain the failure parameters related to the hypothetical breach of the recent dams. According to observations, the failure time (tf) is highly dependent on hydraulic and breach characteristics. Therefore, the tf is considered as a function of these characteristics in the proposed formulas. Based on the performance indices, the values of the determination coefficient (R^2) for the newly proposed Qp relations are equal to 0.94 and 0.91, respectively, in the overtopping and piping failures. This coefficient for the development of the Ver relationship is equal to 0.98, and for the development of tf equations are equal to 0.85 and 0.87, respectively. Since the outflow hydrograph of a breached embankment dam is largely depended on the geometry and evolution time of the breach, the failure hydrographs of real embankments are simulated using a combination of regression analysis and evolutionary algorithms as a case study.