The hydraulic design of a channel or irrigation canal is governed mainly by two factors: (i) quantity of silt in the water carried by the channel and (ii) type of boundary surface of channel. Based on these, we may have three types of channels 1. Alluvial channels 2. Non-alluvial channels 3. Rigid boundary channels or lined channels
Alluvial channels: Alluvial channels are those which are excavated in alluvial soil, such as silt and which carry a lot of silt along with water. The boundary or the perimeter of such a channel is therefore made of silt, commonly known as alluvium. The silt content may increase if the velocity of flow is such that it scours the deb and sides of the canal. Similarly, the silt content of water may decrease if the velocities would be to design for the given discharge.
Non-alluvial channels: Non-alluvial channels are those which are excavated in non-alluvial soil (such as loam, clay, hard soil, rock etc). Such channels generally do not have silting problems as water can flow with non-silting velocities without the fear of scouring of sides and bed of the canal
Rigid boundary channels: Rigid boundary channels are those which have sides and bottom made of rigid material. All lined canals fall under this category.