What is a subdrain?

A subdrain refers to a specific component of a drainage system designed to manage groundwater and capture subsurface water. It typically consists of perforated pipes or drains installed below the surface, where gravity flow is not sufficient to carry away water effectively.

In scenarios where natural soil drainage is inadequate or groundwater levels are high, a subdrain plays a crucial role. It collects excess water and redirects it to an appropriate drainage outlet, thus preventing water accumulation and potential damage to structures. This type of system may be used in agricultural fields, around basements, or in areas with heavy clay soils that inhibit surface drainage.

The other options refer to concepts that either involve surface drainage solutions, systems that manage water differently, or do not pertain specifically to the required definition of a subdrain, which focuses on the ability to handle water that cannot flow by gravity alone.