Which of the following best describes a grassed waterway?

A grassed waterway is best described as a natural or constructed channel that is designed to convey water while being reinforced with vegetation, typically grasses. This type of waterway is specifically constructed or modified to manage runoff and reduce soil erosion, thus providing a means for safe drainage of excess water. The resistant vegetation grows in the channel, helping to stabilize the soil and facilitate water flow while minimizing erosion.

In contrast, the other choices do not accurately capture the essential characteristics of a grassed waterway. A concrete channel with vegetation does not reflect the natural element typically involved in grassed waterways, which are usually composed of softer, sustainable materials. An artificial pond with soil absorption emphasizes a different function related to water retention rather than drainage. Lastly, a swale designed for infiltration primarily focuses on capturing water within the landscape rather than conveying it as a grassed waterway does. Thus, the distinguishing feature of a grassed waterway is its combination of water conveyance and reinforcement through vegetation.