Appendix A: Design Procedure for Riprap Armor
DESIGN PROCEDURE FOR RIPRAP ARMOR
The guidance presented herein is being used by the U.S. Army Corps of Engineers
(EM 1110-2-1601) and applies to riprap design for the following conditions:
Open channels are immediately downstream of stilling basins or other highly
Channel slopes less than 2 percent.
The ability of riprap revetment to resist the erosive forces of channel flow depends on
the interrelation of the following stone and channel factors:
stone shape, size, weight, durability, gradation; riprap layer thickness; and
channel side slopes, roughness, shape, alignment, and invert slope.
The bed material and local scour characteristics determine the design of toe
protection, which is essential for riprap revetment stability. The bank material and
groundwater conditions affect the need for filters between the riprap and underlying material.
Construction quality control of both stone production and riprap placement is essential for
successful bank protection. Riprap protection for flood-control channels and appurtenant
structures should be designed so that any flood that could reasonably be expected to occur
during the service life of the channel or structure would not cause damage exceeding nominal
maintenance. While the procedures presented herein yield definite stone sizes, results should
be used for guidance purposes and revised if appropriate, based on experience with specific