A river training work is generally required when river is

Explanation:

River Training Works

River training works are constructed for several reasons but the fundamental objective is to restrict the horizontal movement of the river channel along a certain alignment.

The measures are adopted to train the river because rivers in alluvial flood plains are prone to meandering and hence cause a lot of damage to life and property.

Additional Information Meandering

• Meandering is considered a wave phenomenon.
• A meander is formed when moving water in a stream erodes the outer banks and widens its valley and the inner part of the river has less energy and deposits what it is carrying.
• A meandering channel tends to be deeper towards the concave bank and progressively gets shallower towards the convex bank.