Embankment dam break: Uncertainty of outflow based on fuzzy representation of breach formation parameters

Abstract

The failure of an embankment dam results in an outflow hydrograph with catastrophic consequences to the downstream valley, especially when populations at risk are located close to the dam. The estimation of the outflow from the created breach is the key information for delineating the area at risk and the estimation of the associated potential consequences. This paper studies the uncertainty of breach parameter estimations by using fuzzy set theory and its impact on the outflow from the breach. For simulating the breach formation and the development of outflow hydrograph, a simplified analytical solver, which was recently presented by the authors, is used. The solver is based on the assumptions of prismatic reservoir, the parabolic shape of the breach and the constant rate of vertical erosion. The parameters, which are represented as triangular fuzzy numbers, are: (i) the characteristic parameter of the parabolic shape of the breach and (ii) the rate of vertical erosion. It was concluded that the approach for estimating the outflow differs, depending on the cause of fuzziness. The approach for estimating the outflow differs according to the parameter which exhibits fuzziness in its estimation. In fact, the uncertainty of outflow is to a great extent dependent on the uncertainty of estimation of vertical erosion and to a much lesser extent on the characteristic of the breach shape.