Uncertainty Analysis of Routed Outflow in Rockfill Dams

Detention rockfill dams are an easy and common tool for f lood control. Due to their coarse pores, the flow in void spaces is turbulent and non-Darcy. Diff erent relationships introduced by researchers are used to define the hydraulics of the f low within the rockf ill materials. The present research is aimed at gaining a better understanding of the diff erence among these relationships and the sources of uncertainty associated with the diff erent parameters of each of the relationships. To examine the importance of various factors on the uncertainty of the outf low hydrograph, sensitivity analysis was conducted. For this purpose, a rockf ill mass was provided, f if teen random samples of the mass selected, and then the physical characteristics of the material were measured or estimated. Also, some flood routing tests have been conducted. In these tests a physical model of a dam was installed and downstream water level was measured for diff erent outflow rates. While the downstream water level was considered as certain variable but other parameters were seen as stochastic (stochastic parameters are considered as random variables) and outf low discharge as an output uncertain parameter. Uncertainty analysis has been conducted for different points of the outflow hydrograph by employing available methods. The results show that the Samani et al. and McCorocoudale et al. relationships have the lowest and highest uncertainty, respectively. The sensitivity analysis demonstrates diff erent levels of sensitivity accompanied each of the relationship parameters which results in diff erent ef - f ects on the total uncertainty of the relationships