Design of stepped-block spillways

This design guide provides a framework within which an experience engineer can consider the use of stepped blocks as a form of spillway construction or protection to embankments subject to overtopping or other drainage structures subject to high velocity flow. It covers the practical design of spillways using stepped blocks for structures with erodible slopes such as dams, irrigation schemes, highways, diversion channels, and river and canal embankments. The emphasis is on the strategic nature of spillways and embankment protection and the guide warns against the uninformed use of apparent ‘low-cost’ protection such as stepped blocks without the full understanding that this guide recommends. The information provided here is the most up-to-date at the time of writing. Several areas of scientific understanding of the processes involved is still incomplete and yet to be improved by future research ad experience. These areas present the limitations, but this guide sets out an approach that is appropriately conservative as well as being generally acceptable to the practising engineer.