Which combination yields the greatest runoff coefficient?

Which combination yields the greatest runoff coefficient?

• A. paved surface + dense grass
• B. sandy soil + dense grass
• C. paved surface + bare soil
• D. rocky surface + poor grass

Answer: (C)

The combination of a paved surface with bare soil yields the greatest runoff coefficient due to the inherent properties of both surfaces involved. A paved surface is typically impermeable, meaning it does not allow water to infiltrate the ground. As a result, any precipitation that falls on this type of surface is likely to flow over it and contribute to runoff. In contrast, the presence of bare soil provides minimal absorption; it generally cannot hold much water, especially if it is compacted or has little to no vegetation cover. Without plant roots and ground cover, the bare soil is less effective at absorbing moisture, leading to higher runoff. This combination creates an environment where nearly all precipitation results in runoff, maximizing the runoff coefficient, which is a measure of how effectively an area can drain. Other combinations like a paved surface with dense grass or sandy soil with dense grass would not yield as high a runoff coefficient, as vegetation can slow down and absorb some water, while sandy soils may facilitate infiltration, reducing the overall runoff.

The combination of a paved surface with bare soil yields the greatest runoff coefficient due to the inherent properties of both surfaces involved. A paved surface is typically impermeable, meaning it does not allow water to infiltrate the ground. As a result, any precipitation that falls on this type of surface is likely to flow over it and contribute to runoff.

In contrast, the presence of bare soil provides minimal absorption; it generally cannot hold much water, especially if it is compacted or has little to no vegetation cover. Without plant roots and ground cover, the bare soil is less effective at absorbing moisture, leading to higher runoff.

This combination creates an environment where nearly all precipitation results in runoff, maximizing the runoff coefficient, which is a measure of how effectively an area can drain. Other combinations like a paved surface with dense grass or sandy soil with dense grass would not yield as high a runoff coefficient, as vegetation can slow down and absorb some water, while sandy soils may facilitate infiltration, reducing the overall runoff.