Embankment dam spillways and energy dissipators

For the last fifty years, the design floods of a number of embankment dams were re-evaluated and the revised spillway outflows are often larger than the original design discharges. Several embankment overtopping protection systems were developed for earthfill structures, and the applications range from river dykes to tsunami protections including embankment dams. Well-known designs include timber cribs, sheet-piles, riprap and gabions, reinforced earth, minimum energy loss (MEL) weirs, embankment overflow stepped spillways and the precast concrete block protection systems. In this review, several design techniques are reviewed and discussed based upon prototype experiences. A critical analysis of their performances highlights that a safe operation of embankment dam spillways and associated energy dissipators relies upon a sound design and a good quality of construction, suitable flow conditions, together with regular maintenance.