Realistic system reliability estimates in design of levee systems

Abstract

Reliability-based design of levee systems requires proper treatment of spatial variability in reliability analysis. In practice, this is often dealt with by standardized factors that represent the typical spatial variability. Such factors are then used to upscale cross-sectional reliability to system reliability. As for instance choices in schematization and definition of parameter distributions influence the exact meaning of a cross-sectional reliability calculation, these choices also determine what factors should be used. For instance, combination of factors aimed at upscaling ﾑrepresentativeﾒ cross-sectional reliability estimates with a cross-section that represents the worst possible cross section results in excessively low estimates of system reliability. In this paper we investigate the treatment of uncertainty in the reinforcement design of a riverine levee that is sensitive to inner slope instability and piping erosion. By integrally looking at the schematization of cross-sections and how this translates to system reliability we determine realistic bounds for system reliability. By iteratively improving consistency in assumptions for different cross sections we substantiate that the envisaged reinforcement will result in a sufficiently reliable levee for the years to come.