Question

what is drainage?
give examples
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Answer 1

Drainage is the natural or artificial removal of a surface's water and sub surface water from an area with excess of water .

Point drainage and channel drainage are some types of drainage

Answer 2

Drainage can be either natural or artificial. Many areas have some natural drainage; this means that excess water flows from the farmers fields to swamps or to lakes and rivers... There are two types of artificial drainage; surface drainage and subsurface drainage