Rapid retreat rates of sea cliffs exposing glacial material are a widespread problem, especially in Atlantic Canada, and one that will continue. Prediction of retreat rates at specific sites involves many variables, but a factor that has commonly been overlooked in such prediction is the slope of the bedrock surface under the glacial material. A glaciated bedrock platform is generally necessary to establish a stable situation of temporary equilibrium, and as sea- level rises, the bedrock slope determines the location of the new equilib- rium position. An example from Nova Scotia shows that bedrock slope is so low on some coasts that the only long- range limiting factor is kinetic, i.e. how fast hydrodynamic energy can remove glacial material. Prediction of coastal retreat scenarios requires better information on the bedrock surface than is commonly available.