Surface drainage system is a process that entails the removal of water that collects on the land surface. The system consists of shallow ditches and should embrace land smoothing or land grading. Surface drainage system is proper for all slowly permeable soils and for soils with clay subsoil.
Meanwhile, subsurface drainage system is either natural or artificial. Worth-noting is that it occurs beneath the ground surface. This type of a drainage system is used when the drainage problem is mainly that of shallow water tables. Subsurface field drainage systems are differentiated as regular systems and controlled systems; and horizontal or vertical systems.
Another characteristic of a surface drainage system is that it consists of an outlet channel, lateral ditches, and field ditches. In this system, water is carried to the outlet channel by lateral ditches. These receive water from field ditches or sometimes from the surface of the field. Surface drainage affects the water table by minimising the volume of water entering the soil profile. The system can be classified into Regular Surface Drainage System and Controlled Surface Drainage System.
On the contrary, subsurface drainage systems have horizontal or slightly sloping channels made in the soil. These can be open ditches, trenches, filled with brushwood and a soil cap, filled with stones. They can also be a soil cap, buried pipe drains, tile drains, or mole drains, but they can also consist of a series of wells. The system allows the field drains (or laterals) to release water into the collector or main system either by gravity or by pumping.