Types of weirs are
a) Based on materials of construction
1) Masonry weir
2) Rock-fill weir
3) Concrete weir
b) Based on use and function
1) Storage weir
2) Pick-up weir
3) Diversion weir
4) Waste weir
c) Based on design
1) Gravity weir
2) Non gravity weir
1. Masonry Weir i. It consists of a vertical drop wall or crest wall with or without crest gates and an impervious floor ii. Cut off piles are provided at the upstream and downstream ends of the impervious floor iii. Aprons are also provided at both upstream and downstream side to prevent scouring iv. The raised masonry crest does the most ponding and a small part is done by the crest shutter v. These weirs are suitable on any foundation
2. Rock fill weir i. This weir consists of a body wall and dry stones are laid on the upstream and downstream side ii. It requires large quantity of stones iii. These weirs are unsuitable for soft foundation where difference between weir crest and downstream river bed does not exceed 3m iv. An example of this type of weir is Okhala weir on Yamuna river near Delhi
3. Concrete Weir i. This is comparatively new type of weir ii. When water passes over it, hydraulic jump is formed on the downstream glacis to dissipate energy of flowing water iii. They are exclusively used nowadays, especially on permeable foundations
4. Pick-up Weir i. It is a solid weir with crest gates constructed in concrete or stone masonry ii. It is constructed some distance downstream of dam to form a large reservoir to raise the water level upto FSL of canal iii. Pick-up weirs are constructed under following situations: a) Command area is not near the reservoir b) Canal has to run idle c) The terrain is geographically difficult so that canal alignment is very costly or impossible