PERFORMANCE EVALUATION OF DAM FAILURE ANALYSIS MODELS

Abstract

Dam failure analysis is a study conducted by assuming a hypothetical dam break situation to predict the potential flooding conditions that would result downstream of the dam from it's partial or complete (catastrophic) failure. The various best known and widely used mathematical models used for simulating dam failure are the MIKEI 1, HEC-RAS and NWS-DAMBRK softwares. These models show variation in their simulation results as they differ from one another due to varying approaches involved in each of the models in dealing with different components of dam failure, including the numerical schemes followed. Therefore, the performance of these dam failure analysis models were evaluated by comparing the reconstituted flood wave resulted from the failure of Machhu dam II which happened on 11 th August 1979. The maximum stage profile simulated by these models were compared with the high level marks observed along the river reach after the passage of the flood wave which resulted from the failure of Machhu 11 dam. Further, various other pertinent characteristics of the flood hydrographs simulated by these dam failure analysis models were also compared with each other to understand the variation in their relative performances. On the basis of the comparison of the simulated peak stage profile with the observed values, the simulation results of MIKEI 1 are much closer to the observed values along the downstream channel than the other two models. The peak discharge values of the HEC-RAS simulated hydrograph are higher than that of the MIKE] I and DAMBRK models at all points, except at the location immediately below the failed dam. In the location immediately below the dam, the peak discharge value of the DAMBRK simulated hydrograph is higher than those values from the other two models. Even though the breach parameters used in all these models are the same, the breach development is not the same in the three models. DAMBRK shows a high rate of attenuation during the initial portions of the downstream reach of Machhu dam I1. Both the MIKEI 1 and DAMBRK models have the features to represent the results in a user friendly form such as by animation. In DAMBRK model there is a limitation in the use of number of channel locations at which the discharge hydrograph can be obtained which is a maximum of six.