Lining the channel with concrete provides a smoother surface over which the water can flow, thereby reducing friction and also increasing the velocity of the stream.
(Lining the channel with concrete; provides; a smoother surface over which the water can flow) (the water; can flow; L:a smoother surface)
Lining the channel with concrete the water
provides can flow
a smoother surface over which the water can flow
L:a smoother surface