Ditches are moderately sized channels created to intercept surface runoff before it can reach the infrastructure’s location. Generally speaking, ditches have a trapezoidal cross-section, and can be unpaved or paved. They are made to run more or less longitudinally to the axis of the infrastructure, immediately above the head of the structure.

The water flow inside the ditches is determined by the slope of the ditch, which matches that of the earth it is dug into; this flow does not necessary follow the same direction as the gully water.