12.5.4. Bank Protection Banks caving due to wave action or erosive action of river flow can lead to river breach causing large amount of losses in terms of human life, property, agriculture, and other utilities. Bank protection measures are, therefore, important to prevent bank failures.
Bank protection measures provide a shield against erosion of bank material and maintain the alignment of banks. These can be of either direct or indirect type. Indirect bank protection measures, such as spurs are not constructed directly on the bank. But, direct bank protection measures, such as revetment, riprap, etc. are constructed on the bank itself.
For providing direct bank protection, all irregularities on the bank surface are removed, and the bank is graded to an acceptable slope. The value of this slope for banks of alluvial material containing little gravel ranges between 1(V) : 5( H) to 1(V) : 6(H) below low water line and between 1(V) : 3(H) to 1(V) : 4(H) above this line (16). A layer (several centimetres thick) of coarse material, such as gravel or broken stone is spread on this slope and the chosen revetment is laid on this layer.
Revetments are structures aligned parallel to the current and used to protect eroding banks. These revetments can be of different types such as the woven willow mattress, the framed willow mattress, the lumber mattress, the reinforced asphalt mattress, and the articulated concrete mattress. These types of bank protection measures are usually very costly, and have been used mainly in the USA and Europe.
