Riprap sizing at toe of embankment slopes

A pilot study was conducted to evaluate existing rock-sizing techniques for stabilizing transition toes of embankments. The U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers (Campbell) procedures were applied and determined to be conservative in sizing riprap. Embankment-overtopping tests were conducted placing 8.9, 13.0, and 19.8-cm-diameter stones at the slope transition. An alternative method was developed for sizing toe rock based upon the unit discharge, embankment slope, and flow concentration. The results indicate that an embankment toe can be stabilized with a smaller median stone size than previously anticipated. These results were verified for unit discharges of 0.54 m(3)/s/m or less.