What is typically the maximum runoff coefficient for impervious surfaces like asphalt?

What is typically the maximum runoff coefficient for impervious surfaces like asphalt?

• A. A. 0.85
• B. B. 0.70
• C. C. 0.90
• D. D. 1.00

Answer: (C)

The maximum runoff coefficient for impervious surfaces such as asphalt is often considered to be approximately 0.90. This value indicates a high level of runoff occurring when precipitation falls on such surfaces. Impervious surfaces do not allow water to infiltrate into the ground, leading to most of the rainfall being converted into runoff. A coefficient of 0.90 suggests that 90% of the precipitation contributes to runoff, reflecting the effective nature of these surfaces in channeling water away, which is critical for hydrological calculations and flood management. While values slightly lower than 0.90 may be used in certain contexts (such as 0.85), they do not represent the typical maximum for these types of surfaces. A coefficient of 1.00, indicating that all precipitation becomes runoff without any infiltration, is theoretically possible but not realistic for most real-world scenarios since some minimal storage or evaporation might occur. Therefore, the chosen maximum value of 0.90 accurately represents the expected behavior of runoff from impervious surfaces like asphalt.

The maximum runoff coefficient for impervious surfaces such as asphalt is often considered to be approximately 0.90. This value indicates a high level of runoff occurring when precipitation falls on such surfaces. Impervious surfaces do not allow water to infiltrate into the ground, leading to most of the rainfall being converted into runoff. A coefficient of 0.90 suggests that 90% of the precipitation contributes to runoff, reflecting the effective nature of these surfaces in channeling water away, which is critical for hydrological calculations and flood management.

While values slightly lower than 0.90 may be used in certain contexts (such as 0.85), they do not represent the typical maximum for these types of surfaces. A coefficient of 1.00, indicating that all precipitation becomes runoff without any infiltration, is theoretically possible but not realistic for most real-world scenarios since some minimal storage or evaporation might occur. Therefore, the chosen maximum value of 0.90 accurately represents the expected behavior of runoff from impervious surfaces like asphalt.