FLOOD06940

• County: Statewide
• Basin: Statewide
• Title: Corps of Engineers Riprap Guidance
• Date: 7/1/1970
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Community File

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EM 1110-2-1601
1 July 70

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of riprap revetment should be terminated at the top of the levee or on the

slope at the freeboard level above the design water surface, as shown in end

view in plate 38. Consideration should be given to the economy of termi-

nating the top of the revetment below the levee top or design water surface

plus freeboard when the design flood with moderate velocities will overtop

the revetment only for a short time. The upstream and downstream ends of

riprap revetment should be protected against erosion by increasing the re-

vetment thickness or extending the revetment to areas of noneroding veloci-

ties. The fOllpwing criteria apply to the alternative methods of end protection

illustrated in plate 38.

(1) Method A. For riprap revetments 12 in. thick, the normal riprap

layer should be extended to areas where velocities will not erode the natural

channel banks.

(2) Method B. For riprap revetments exceeding 12 in. in thickness,

one or more reductions in riprap thickness and stone size may be adopted for

a distance ain which velocities decrease to a noneroding natural channel

velocity.

(3) Method C. For all riprap revetm.ents that do not terminate in non-

eroding na.tural channel velocities, the ends of the revetment should be en-

larged, as shown in plate 38. The dimensions a and b should be 3 and 2

times the layer thickness', respectively.

(4) Method D. For riprap revetments exceeding 24 in. in thickness,

consideration should be given to the economy of adopting method D instead of

method C. The stub, with thicknes s T 3 equal to T l' should be placed at the

extremity of the revetment proper and the revetment extended a distance a

with smaller stone size and thickness T2 to a noneroding location. The

depth b should equal 2.5 times T 1 .

1. Riprap Placement. The common methods of riprap placement are

hand placing; machine placing, such as from a skip, dragline, or some form

of bucket; and duznping from trucks and spreading by bulldozer. Hand place-

ment produces the best riprap revetment, but it is the most expensive method

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