Summary, conclusions and recommendations

The stepped channel design has been used for more than 3,500 years. The Greek and Minoan engineers were probably the first to design an overflow stepped weir and stepped storm waterways respectively. Later, Roman, Moslem, Mughal and Spanish designers used a similar technique. At the end of the 19th century, a significant number of dams were built with overflow stepped spillways (e.g. Schuyler in 1909, Wegmann in 1911 and Kelen in 1933). Since the beginning of the 20th century, stepped chutes have been designed more specifically to dissipate flow energy (e.g. New Croton Dam). The steps increase significantly the rate of energy dissipation taking place on the channel face, reducing the size of the required downstream energy dissipation and the risks of scouring. Recently, new construction materials (e.g. RCC, strengthened gabions) have increased the interest for stepped channels and spillways. The construction of stepped chutes is compatible with the slipforming and placing methods of roller compacted concrete, with the construction techniques of gabion dams and with the precast concrete block system technique.