Understanding Temporary Spurs in River Engineering

Temporary spurs are structures built into a river or stream channel, usually perpendicular or at an angle to the bank. Their primary purpose is river training, which involves guiding the flow of water, protecting the banks from erosion, and controlling sedimentation. These structures are called 'temporary' because they are often constructed for a specific period or purpose, like during a flood season or while permanent measures are being implemented, and are not designed for long-term existence without maintenance.

Exploring the Options

Let's look at the provided options and understand what each term means:

• Weirs: A weir is a barrier built across a river or stream to alter the flow characteristics. Weirs are typically used to raise the water level upstream, measure flow rate, or create a small pond. They are generally considered more permanent structures than temporary spurs.
• Canals: A canal is an artificial waterway constructed for navigation, drainage, or irrigation purposes. Canals are fundamentally different from spurs, which are bank protection or flow diversion structures within a natural or existing channel.
• Bunds: A bund is an embankment or dike, often made of earth, used to retain or divert water. Bunds can be constructed temporarily for flood control, irrigation, or to create enclosed areas of water. Temporary bunds built along a river bank or into the flow serve a similar function to temporary spurs – diverting flow away from the bank, protecting against erosion, or directing water towards a desired channel.
• Barrages: A barrage is a type of low-head dam that consists of a series of gates that can be opened or closed to control the amount of water passing through. Barrages are used for irrigation, diversion, or flood control and are permanent, substantial structures.

Relating Temporary Spurs to Bunds

Based on the definitions, temporary spurs and bunds share functional similarities, especially when bunds are used as temporary embankments along a river to influence flow patterns or protect banks. A temporary spur is essentially a form of temporary embankment or bund projecting into the river.

Therefore, temporary spurs are also known as Bunds, particularly in the context of temporary river training works or protective embankments.

Why Other Options Are Not Synonyms

• Weirs and Barrages are permanent structures used to control water levels or flow differently than spurs.
• Canals are entirely different types of waterways.

The term 'Bunds' is often used interchangeably with temporary spurs, especially when referring to simple, temporary earth embankments built for river bank protection or flow diversion.

Revision Table: River Structures Terminology

Additional Information on River Training Structures

River training works are crucial for managing rivers for various purposes, including flood control, navigation, and preventing erosion. These works can be broadly classified into:

• Guide Banks: Structures built parallel to the river flow to guide it smoothly through structures like bridges or barrages.
• Spurs or Groynes: Structures projecting from the bank into the river flow. They can be attractive (drawing flow towards them), repellent (deflecting flow away), or ordinary. Their design (length, angle, permeability) depends on the specific river conditions and training objective. Spurs can be temporary (like bunds) or permanent (made of stronger materials like concrete, stone, or piles).
• Revetments: Bank protection measures like pitching (laying stones or concrete blocks) or using mattresses (like gabion or Reno mattresses) to prevent erosion.
• Cutoffs: Shortening the river course by cutting through meander loops.

Temporary spurs, or bunds used as temporary spurs, are often the first line of defense or a quick solution employed during critical periods or as part of staged construction of permanent measures.