Hydraulic Design of Stepped Spillways and Downstream Energy Dissipators

Abstract

Stepped channels and spillways have been used for centuries. Recently, new construction materials, (e.g. RCC, gabions) and design techniques (e.g. embankment overtopping protection) have increased the interest in stepped chutes. The steps produce considerable energy dissipation along the chute and reduce the size of the required downstream energy dissipation basin. This paper reviews the characteristics of modern stepped spillways. The basic flow patterns are described. Basic equations are developed, taking into account the free surface aeration in skimming flows. The calculations of the residual energy to be dissipated in the downstream dissipator are discussed. Simple design guidelines for the downstream energy dissipators are provided for use by professionals.