Hydraulics of stepped weirs and dam spillways: engineering challenges, labyrinths of research

Abstract

Stepped weirs and dam spillways have been increasingly used for handling flood releases, due to their inherent benefits, particularly those related to energy dissipation. Among the diversity of construction techniques for which a stepped chute turns out to be an attractive solution, the popularity of roller compacted concrete placement on new and rehabilitated dams has prompted interest in researching the hydraulics of stepped spillways, for medium to large unit discharges. In this paper, some main applications of stepped chutes are briefly described, with a particular focus on recent engineering challenges on spillways over concrete gravity or RCC dams, questions raised and some answers proposed. Some peculiar, eventually paradoxical aspects of the non-aerated and self-aerated skimming flows on steeply sloping chutes are addressed, in light of the self-aerated flow on smooth spillways. Later, a brief review of possible future research topics in this captivating field of research is included.