What is the function of a pipe slope drain (PSD)?

A pipe slope drain (PSD) serves the essential function of allowing water to flow down a slope while minimizing the risk of erosion. When rainwater or surface runoff travels down a sloped surface, it has the potential to pick up soil particles and accelerate erosion. The design of a pipe slope drain helps to manage this flow by directing water safely and efficiently down the slope, reducing the energy of the flowing water and preventing it from creating channels or rills that can lead to further erosion.

Option A, while it mentions redirecting water, inaccurately implies that the primary function of a PSD is for storage, which is not its purpose. Option C's focus on collecting rainwater for irrigation does not align with the PSD's role in managing runoff flow on slopes. Finally, option D discusses sediment filtration, which is typically the purpose of sediment control measures rather than a function of a pipe slope drain. Therefore, the correct understanding is that the primary role of a pipe slope drain is to facilitate the safe dissipation of water down a slope while preventing soil erosion.