Highways are often located adjacent to streams, lakes, and coastal areas. Channel and shore protection must be provided wherever the need is apparent or the risk is high.
In other circumstances, where the possibility of damage to the roadway or adjacent land is not clear or risk is low, it may be acceptable to delay construction of embankment stabilization measures until a problem actually develops.
There are a number of methods of protecting the roadway from damage due to erosion. The simplest and surest of these is to locate the highway away from the erosive forces. This should always be considered, although it is rarely the most economical alternative. The most common method used to protect the roadway is to line the roadway embankment with a material that is resistant to erosion such as concrete or rock. Another method is to reduce the force of the water that would cause the erosion. Such bank protection structures retard the flow of the water while at the same time allowing a sedimentation buildup to reverse the trend of erosion and replace material that may have been lost. A final method of protection that should be considered is redirecting the eroding force away from the embankment. This may be done by the use of jetties or baffles, or even by creating a new channel.
Any combination of the above methods may be used to achieve the desired protection. The design of the protective features should be commensurate with the importance of the roadway being protected and with the risks involved. (See Highway Drainage Guidelines, Vol. III, Erosion and Sediment Control, AASHTO; “Design of Riprap Revetment,” HEC 11, FHWA; and “Design of Roadside Channels with Flexible Linings,” HEC 15, FHWA.)
