A series of flume experiments was performed as a part of a comprehensive study of rock erosion in spillway channels. The flume provided a controlled environment in which different flow rates and block configurations could be examined. The results of the experiments suggest that there is a strong influence of block orientation with respect to flow direction on the block erodibility threshold. Similarly, increasing flow turbulence intensity and/or increasing block protrusion height were also found to significantly lower the block erodibility threshold.