Reinforced Rockfill for Construction Flood Control

The technique of using downstream zones of reinforced rockfill to enable the passage of major construction floods over a partly completed enbankment dam has great economic attraction. Three dams have been constructed in southern Africa using this approach, but their performance was less than satisfactory. The methods used in designing the rockfill reinforcement are outlined and the problems experienced at the three sites are covered with emphasis being placed on the major failure that occurred at the Xonxa dam. It is concluded that this construction technique can be employed successfully provided care is taken to prevent undermining of the downstream flanks and damage to the mesh by debris carried by the flood waters.