What does a subdrain primarily collect?

A subdrain is specifically designed to collect groundwater. Its primary function is to relieve excess moisture from the soil by channeling it away, usually to prevent waterlogging and to help manage soil saturation levels. This is particularly important in areas where the water table is high or in soils with poor drainage characteristics.

Unlike surface drainage systems that handle surface runoff or rainwater, subdrains operate below the ground, targeting the movement of water through the soil profile. They effectively help in maintaining the stability of foundations and roadways, as well as improving the overall drainage of a site. This focus on groundwater highlights the unique role subdrains play in drainage and stormwater management systems, differentiating them from other forms of drainage that address direct precipitation or surface water runoff.