What is a 'swale' in the context of stormwater management?

A swale, in the context of stormwater management, is a specifically designed landscape feature that channels and manages stormwater runoff. It is typically a shallow, elongated depression that allows water to flow through and be absorbed into the ground, helping to reduce the volume of runoff and filter pollutants. Swales are often vegetated, which enhances their ability to absorb and treat the water naturally through soil and plant processes. This makes them an effective means of managing stormwater in a manner that promotes infiltration, improves water quality, and reduces the risk of flooding.

The other options do not accurately define what a swale is. For instance, a drainage pipe is a conduit for carrying water away, while a construction material for roads does not relate to stormwater management features at all. A measurement for water levels is more relevant to hydrology but does not describe a physical structure like a swale. Thus, swales represent an essential component of green infrastructure aimed at sustainable stormwater management.