When a channel is protected on the bed and side with protecting mater said to be in:

Explanation:

A canal with boundaries of easily erodible loose soils is called a Mobile boundary canal

1. Mobile boundary canal: 

• If a channel boundary is composed of loose sedimentary particles moving under the action of flowing water, that type of canal is called a Mobile boundary canal and the channel is called a mobile boundary channel.
• Example: An alluvial canal is a mobile boundary canal transporting the same type of material comprising the channel perimeter.
• Resistance not depend only on the boundary surface but also on the condition of the bank and bed.

2. Rigid boundary canals: 

• Chanal whose bed and banks are made up of non-erodible material is known as rigid boundary canal and the channel is known as rigid boundary channel.
• Eaxmple: Non alluvial canal
• Resistance to water depends only on the nature of the boundary surface.

Non-alluvial canal: 

• Canal that has been lined with some suitable material to provide a rigid bed and banks so as to avoid the problem associated with alluvial boundaries.

Permanent regime canal: 

• A permanent regime canal is one that is fed by a permanent source of supply.
• It is a well-graded channel and is provided with permanent regulation and distribution works.
• This type of channel is not easily scoured and hence chances of change in longitudinal slope is less