What must be done to the exposed surface of an embankment?

Seeding the exposed surface of an embankment with perennial grasses is an essential practice for several reasons. This method helps establish vegetation, which plays a crucial role in preventing soil erosion by stabilizing the soil with roots. The vegetation also aids in water absorption, reducing runoff and promoting the infiltration of water into the soil. By growing perennial grasses, you create a protective layer that not only reinforces the embankment structure but also contributes to the overall health of the surrounding ecosystem.

In contrast, paving the surface may not allow for proper drainage and can lead to runoff issues, while leaving the surface bare exposes it to erosion from wind and water. Covering the embankment with gravel could also lead to drainage problems and does not provide the same ecosystem benefits as establishing a layer of grass. Therefore, seeding with perennial grasses is the most effective and environmentally sound choice for managing and protecting an embankment's exposed surface.