Excessive erosion can weaken the sides of the road itself. Ditch lining is the most common way to prevent erosion. Linings can be of natural soil, vegetative, or paved. The material used depends on flow velocity. The following table illustrates the types of lining appropriate for various flow velocities.
Engineers use similar tables when designing waterways.
Road managers can also use it empirically. If a lined, well-maintained ditch is eroding, then crews should apply a lining for a higher flow. If problems persist, the agency should consult a qualified engineer. In addition to minimizing erosion in low-flow ditches, vegetation removes roadway pollutants from runoff water. Here are a few guidelines to remember about vegetation in ditches .