Evaluation of Superelevation in Open Channel Bends with Probabilistic Analysis Methods

A probabilistic — and uncertainty analysis for the failure modes of a hydraulic structure is presented in this paper. First, a general approach for such kind of analysis is presented, followed by a case study. The study deals with the Ziaran diversion dam in Iran. Data has been collected during previous studies of this dam. In particular one failure mechanism is investigated in this paper in detail: overtopping by superelevation of the bend flume in the Ziaran Dam. This study focuses on the downstream water surface elevation during the flow considering the flume's actual discharge and roughness. Superelevation in the Ziaran Flume has led to severe erosion of the bank and to undermining of the structure. Therefore, this study aims to cast lights on the cause of overtopping by superelevation. By means of direct observation on the flume's hydraulic performance, during full discharge, and from generalization of the field data, a more reliable prediction method of the magnitude of superelevation has become possible. The probabilistic analysis will show to have several advantages in comparison with deterministic analysis methods.