River Training Works are provided to confine the flow of water in a given cross section and in a particualr alignment i.e., straight and non-twisted approach to bridge structure. These may be Guide Bunds and Spurs.
These are provided for guiding the flow of water in a given cross section and in particular
alignment i.e., straight and non-twisted approach to bridge structure. Guide bunds also
prevent the river cutting into the bridge approaches, causing breaches and forming deep scour at abutments.
These objectives are achieved by giving Guide Bunds of suitable shape, providing adequate length by adding
curved heads and by giving suitable protection to exposed faces against river attack.
Constriction of waterway at bridges is effected by extending the approach banks to cover spill area or part of active channel. Such constriction causes obstruction to flow and Guide bunds are required for guiding flow smoothly through the bridge.
The course of main channel may change on account of progressive movement of meanders or formation and movement of islands in braided rivers. In the process, the stream may directly hit/attack the embankments on bridge approaches. Under such conditions it becomes obligatory to provide guide bunds in order to pass the river discharge axially with as uniform flow through the bridge as possible.
Spurs or groynes are structures constructed in the river transverse to the bank to achieve any of the following objectives. Deflecting spurs are commonly used for protection of riverbank from erosion either in a straight or a curved reach. When navigation channel has inadequate depth, spurs are provided to constrict the channel width so that depth is increased suitably by bed scour. Closure of bye channels may be required to be made in the interest of navigation or as a river training measure. It is possible to achieve this purpose by means of spurs. In the approaches to bridges and water intakes, shifting position of the channel is some times required to be stabilised. Such stabilisation can be effected up providing attracting spurs.