River Training: Types, Components and Advantages | Civil Engineering Optional Notes for UPSC PDF Download

Functions of River Training Works

• Ensuring a straight path for the weir, avoiding unnecessary bends.
• Preventing the weir from being bypassed by the river, maintaining its effectiveness.
• Protecting additional land from being submerged due to water buildup.
• Preventing erosion along the river banks, maintaining stability.
• Promoting a steady and central flow of river water to prevent shifts in the river's course.

Types of River Training Works

1. High Water Training

• High water training is implemented to manage the flow of river water for discharge purposes.
• Purpose: The primary aim of high water training works is to control and redirect floodwaters, thereby preventing catastrophic events. It involves raising the marginal embankments to suitable levels for effective flood management and channel enhancement.
• Actions Taken:
  • Adjustment of embankment elevations for proper alignment and floodwater disposal.
  • Implementation of measures to enhance channel efficiency.

2. Low Water Training

• Low water training focuses on regulating the depth of river water.
• Objective: The primary goal of low water training is to ensure adequate water depth essential for inland navigation, particularly in dry weather conditions, such as during summer.
• Methods:
  • Channel width reduction during low water periods through the use of groynes to achieve the desired depth.

3. Mean Water Training

• Mean water training is a crucial method used for the training of sediments.
• It ensures the smooth disposal of the bed load to maintain the suspended sediment load and the channel size.
• Mean water training stands out as the most significant type of river water training.
• During river training, water levels are adjusted to modify the cross-section and alignment to suit the young river phase.
• Consideration is given to the maturation stage and old age of the river, where maximum sediment movement occurs.
• Even though the highest sediment speed is reached in the young stage, this phase is short-lived.

Components of River Training Works 

River training works consist of various key components that play crucial roles in managing and controlling the flow of rivers. These components are essential for maintaining the stability of riverbanks and protecting surrounding areas from flooding. Let's delve into some of the main elements:

Marginal embankment (dyke or levee)

The marginal embankment, also known as a dyke or levee, is a trapezoidal earthen structure built parallel to the riverbank. Its primary function is to confine floodwaters within its boundaries, thereby reducing the risk of inundation in adjacent areas.
Guide banks are constructed on both sides of a river to safeguard structures from erosion. These embankments, featuring curved heads at their ends, run parallel to the river's flow direction and extend upstream and downstream of hydraulic structure abutments. Originally devised by Bell, they are commonly referred to as Bell's Bund.

• Guide banks protect structures from erosion by directing river flow effectively.
• They ensure the safe passage of water through hydraulic structures without causing damage.
• Bell's Bund, or the Guide bank, serves multiple purposes:
• - It shields barrages from scouring and erosion effects.
• - It facilitates a direct approach to the barrage.
• - It aids in maintaining the river's course without deviation.

Guide banks are instrumental in river training works due to their role in erosion prevention and flow management.

Functions of Guide Banks

Guide banks have dual roles:

• They protect the approach embankment of a bridge from high water discharge.
• The approach embankments run perpendicular from the riverbank to the guide banks in both directions.
• Guide banks aid in directing the river flow in an axial direction.
  

Spurs

• Spurs are temporary permeable structures placed at river bends to safeguard the riverbank from erosion.
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  • These structures extend from the riverbank at an angle of 60 to 75 degrees.
  • The primary function of spurs is to slow down the water flow velocity.
  • They create water pockets upstream where sediments accumulate.

Groynes

• Groynes play a crucial role in river training projects, serving a purpose akin to that of a spur.
• Unlike spurs, groynes are durable, impermeable structures strategically placed along curves to shield river banks from erosion.
• Their primary function is to safeguard the river bank from erosion caused by the water flow.
• Typically, groynes are built at an angle of 60 to 75 degrees with the bank.

Types Of Groynes

• Groynes in river training projects can be oriented either perpendicular to the bank or inclined, pointing upstream or downstream.
• When a groyne points upstream, it is termed as a repelling groyne.
• A repelling groyne is designed to deflect the river flow away from the bank by creating a calm pool at its upstream end.
• This redirection causes the river to veer away from the bank, reducing erosion.
  • A Groyne that points downstream in the river flow is known as an Attracting groyne.
  • This type of Groyne has the characteristic of attracting the river flow towards the bank.
  • A Groyne of shorter length that is perpendicular to the bank is termed as a Deflecting Groyne.
  • A Deflecting Groyne works by deflecting the flow locally.

Functions of Gryones

• Preventing erosion by controlling sediment deposition.
• Stabilizing riverbanks and protecting structures from water flow.
• Redirecting water flow to prevent flooding in certain areas.
• Creating suitable habitats for aquatic life by altering water flow dynamics.

 River Training Works 

• River training structures play a vital role in safeguarding the river banks by controlling the water flow in proximity to the banks.
• They facilitate the formation of calm ponds alongside the banks, aiding in the accumulation of silt in the nearby area.
• Groynes are instrumental in guiding the river along a desired path by attracting, deflecting, or repelling the flow, effectively training the river's course.
• These structures also assist in narrowing the wide river channel to enhance navigational depth.

Advantages of River Training Works 

• Prevention of alterations in the natural course of the river.
• Mitigation of flood risks.
• Protection of river banks against erosion.
• Facilitation of sediment disposal, ensuring a consistent water depth in the flow.

Disadvantages of River Training Works

• River training works can lead to an increase in high flood levels.
• These structures are susceptible to piping failure.
• They can be easily damaged by the force of the river flow.