Criteria for selecting riprap to protect bridge abutments against scour were investigated.
Experiments were conducted with a spill-through abutment under both clear-water and live bed conditions in a laboratory flume.
The riprap size and apron size and extent were varied.
The data were compiled graphically, with dimensionless variables representing riprap size and apron extent on the axes.
A useful relationship was found, with a clear zone of partial failure.
Keywords: bridge scour, riprap, protection, hydraulic modelling, abutment, live bed, mobile bed, riprap apron