TM 5-820-3/AFM 88-5, Chap. 3
b. The relative advantage of providing both ver-
reduced considerably if a riprap-lined, preformed
tical and lateral expansion downstream of an outlet
scour hole is provided, instead of a horizontal blan-
ket at an elevation essentially the same as the outlet
turbulence, rather than direct attack of the
invert. Details of a scheme of riprap protection
termed "performed scour hole lined with riprap"
indicates that the required size of stone may be
are shown in figure 5-13.