How do retaining walls contribute to erosion control?

Retaining walls play a critical role in erosion control by holding soil in place on steep slopes. These structures are designed to support grade changes and prevent the soil behind them from collapsing or sliding down the slope due to gravitational forces or water saturation. By stabilizing the soil, retaining walls help reduce the risk of erosion that can occur from water runoff or natural weathering processes. This stabilization is particularly important in areas where the landscape is inclined, as it ensures that vegetation can establish a root system, enhancing further soil retention and promoting a balanced ecosystem.

The other options do not accurately describe the primary function of retaining walls in the context of erosion control. While excavation of soil is related to some construction activities, it is not a direct benefit of retaining walls concerning erosion prevention. Increasing surface runoff is an undesirable effect that can actually exacerbate erosion rather than prevent it. Aesthetic landscape design is a secondary advantage of retaining walls but does not speak to their critical function in controlling soil erosion. Thus, the primary contribution of retaining walls to erosion control lies in their ability to maintain soil integrity on steep slopes.