River training works is a term used to stabilize a river channel with a certain alignment and certain cross-sections, a river can be trained by diverting its flow into a secondary channel or by performing artificial cutoffs on the main river to reduce flood levels.
It is mainly required for rivers, which flow over fertile pains, it is often known to change its course.
Here we will learn about river training works, types of river training works & much more.
Introduction to river training works:
River training works includes all measures taken to control and regulate river flow and river configuration.
For example: The river Teesta a tributary Ganga, has been shifted more than 150 kilometers to the east.
Another tributary of the Ganges called the Koshi river originates from the Nepal Himalayas and flows in the state of Bihar is known for its frequent changes in its courses.
This causes a huge change for farming and settlements along such rivers.
Objectives of river training works:
- To provide a safe passage for the discharge of water without overflowing the banks, protection of farming, and inhabited areas.
- To prevent the outflow of work, bridges were constructed across the river like weir or aqueduct and the river was put to work in a non-torturous approach.
- Also, protect the river banks from heavy erosion and improve alignment by stabilizing the river channel.
- To drive the river away from the bank on which it can attack.
Types of river training works:
1.High water training:
The disposal of flood water due to such flooding and providing protection from any kind of damage is the main objective.
This is mainly related to the elevation of marginal embankments for the most appropriate alignment and flood disposal.
It is also connected to taking measures for channel improvement for the same purpose.
In short, high water training is training for discharge.
2.Low water training:
The purpose of river training works is to provide sufficient depth of water for inland navigation, during low water seasons i.e. during summers for non-perennial rivers mainly in South India.
This is done by contracting the width of the channel in low water with the help of groynes, so low water training for depth.
Mean water training:
This is mainly carried for the smooth disposal of bed to maintain suspended sediment load and channel size, so that mean water training is training for sediments.
Among all the three types of river, training is the mean water training i.e. training for sediment is the most important task.
Any river training works, water taken to change the cross-section and alignment must be designed that is appropriate for the river phase i.e. the young state.
The stage of maturation and the old age at which the maximum movement of sediments takes place during any period under consideration.
In the young state, i.e., in the high flow state, sediment has a maximum speed but this state remains for a short time only.
In old age, there is a slight movement of sediment in a low state but it persists for a very short time.
Also read: Hydraulic Jump, Canal & Cross Drainage Work
Methods for River Training:
They are earthen constructions built to keep floodwaters within the c/s available between these embankments.
Groynes or Spurs:
It is a structure that is constructed transverse to the flow of the river.
It extends from the bank into the river.
Guide Banks or bonds:
These are earthen embankments to channelize the floodwaters of the river.
In India, this type of bond was first designed by Bell, hence it is known as bell’s bond.
Also read: Open Channel Flow, Culverts & Fish Ladder
A basic function of river training works is to stabilize river channels for moderate flood flow.
A stable channel for medium flood flow is not only necessary to control the flow path of normal and medium flood flow, but also has the positive effect of controlling low flow and high flood flow.