Evaluating the Effect of Downstream Channel Width Variation on Hydraulic Performance of Arched Plan Stepped Spillways

Stepped spillways provide effective energy dissipation and increase spillway capacity without taking up additional land compared to other types of spillways. In present study, a 3D physical model with scale of 1:50 was developed based on Germi-Chay dam in Institute of Soil and Watershed Conservation of Iran. This model was used to assess the impact of downstream channel width variation on performance of arched plan Stepped spillway. In this regard, four ratios of downstream channel width to spillway crest width (Wch/W) ranging from 0.214 to 0.286 were considered. Results of the experiments indicated that for all width ratios, the values of the discharge coefficient increased with increasing the values of the upstream head prior to the submergence state occurrence. Furthermore, in this state, the downstream channel width variations had not significant impact on the discharge coefficient. However, with spillway submerging, the impact of width variations on di