General Principles of Erosion Protection
appears that the toe section is launching more than expected, it can be reinforced simply by
placing additional material at the riverward edge of the remaining section.
With either approach, stone is often chosen for the toe protection material, even if
another technique is selected for the remainder of the armor or structure, because stone toe
protection can be precisely and confidently designed for almost any application.
6.3.2 SPECIFIC GUIDANCE FOR VARIOUS TECHNIQUES
Application of the basic approaches to specific types of work is discussed in the
following paragraphs.
6.3.2.1 Stone Armor
Guidance can be found in Section 7.1.1.
6.3.2.2 Other Self-adjusting Armor
Either dig it in, or use the self-launching technique. The required toe volume for self-
launching can be computed the same way as for stone armor. If the self-launching approach
is to be used where predicted scour is more than a few feet, then stone is recommended for
the toe material.
6.3.2.3 Rigid Armor
Rigid armor should either extend to the predicted scour depth, be combined with a
self-launching technique with required toe volume computed the same way as for stone
armor, or incorporate a flexible mattress at the toe.
6.3.2.4 Flexible Mattress
Similarly, a flexible mattress can be installed to the predicted scour depth, or extended
riverward of the toe of the bank by a horizontal distance at least twice the predicted depth of
scour. Where appropriate, these guidelines may be superseded by the manufacturer's
recommendations. If more than a few feet of scour is predicted, then the use of a
self-launching stone toe should be considered, particularly if it will not be feasible to monitor
toe scour frequently, or to reinforce the toe if required.
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