Lining steep ditches
Natural materials are used to line sides and bottoms of steep ditches. Rock used in liners is mixed so the spaces between large rocks are filled with smaller rock. You must take care with rock sizing.
As ditch depth and steepness increase, rock size must also increase. A good technique is to line the bare ditch bottom and sides with non-woven filter fabric to prevent undercutting and washouts. If flows are over 10 feet per second, use rock as a bottom liner, below the larger rock. Rock must be placed along ditch bottom first, then up the sides. Rock layer thickness should be 5 times the average diameter of the largest fourth of the rocks.
Silt check dams are spaced according to the slope of the ditch bottom (see table). Extend the ends of the silt check to the top of the bank to prevent bypassing and side cutting. Keep the middle part lower and relatively flat so overflows aren’t too concentrated and bypasses are prevented.