Weirs or barrages:
A structure which is built across river to increase water level is known as weir. It is also known as barrage.
The different water levels are increased with respect to time then weir is raised and barrages are constructed.
Gates: are constructed to increase the water level. When it is required to increase the water level the gates are closed and vice versa.
Causes of failure of barrage or weir:
- Damage of floor
- Deterioration of floor due to standing waves
- Scour on upstream and downwards
Classification of weir
Weirs are determined by the types of material.
- Vertical drop weir:
It is made up of masonry which is laid over floor.
- Dry stone slope weir:
It is also known as rock fill weir. It is made up of masonry wall.
- Concrete slope weir:
Such a type of weir which is made up of reinforced cement concrete is known as concrete slope weir.
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