given in the direction of natural slope of ground

given in the direction opposite to natural slope of ground

zero

steeper than 1 in 20

equal to dry weather flow (DWF)

2xDWF

3 x DWF

6xDWF

equal to rainfall

rainfall + DWF

rainfall + 2 DWF

rainfall + 6 DWF

15 cm and 100 cm

15 cm and 300 cm

30 cm and 450 cm

60 cm and 300cm

less strength

difficulty in construction

difficulty in transportation due to heavy weight

less life