Which of the following would generate a longer runoff time (TOC)?

Which of the following would generate a longer runoff time (TOC)?

• A. 300 ft run distance + dense grass + 3% ground slope
• B. 300 ft run distance + dense grass and paved surface + 3% slope
• C. 400 ft run distance + dense grass + 7% slope
• D. 100 ft run distance + poor grass + 1% slope

Answer: (A)

The correct answer involves analyzing the factors that influence runoff time, which include the length of the run distance, surface conditions, and slope. In this scenario, the first option features a 300 ft run distance, dense grass, and a 3% ground slope. Dense grass has a high capacity for absorbing water, which significantly slows down runoff compared to impervious surfaces. The 3% slope is relatively gentle, which further allows for longer retention of water. The combination of these elements creates conditions that promote infiltration and slow down the movement of water across the surface, culminating in a longer runoff time. On the other hand, the other choices vary in ways that decrease runoff times. For instance, the second option includes a paved surface, which is impermeable and speeds up runoff. The third option increases the slope to 7%, which would enhance the speed of water flow. Lastly, the fourth option has a shorter run distance and a more shallow slope, both contributing to shorter runoff times. Thus, the characteristics of dense grass, a moderate slope, and a significant run distance in the first option collectively contribute to the longest runoff time among the choices provided.

The correct answer involves analyzing the factors that influence runoff time, which include the length of the run distance, surface conditions, and slope.

In this scenario, the first option features a 300 ft run distance, dense grass, and a 3% ground slope. Dense grass has a high capacity for absorbing water, which significantly slows down runoff compared to impervious surfaces. The 3% slope is relatively gentle, which further allows for longer retention of water. The combination of these elements creates conditions that promote infiltration and slow down the movement of water across the surface, culminating in a longer runoff time.

On the other hand, the other choices vary in ways that decrease runoff times. For instance, the second option includes a paved surface, which is impermeable and speeds up runoff. The third option increases the slope to 7%, which would enhance the speed of water flow. Lastly, the fourth option has a shorter run distance and a more shallow slope, both contributing to shorter runoff times. Thus, the characteristics of dense grass, a moderate slope, and a significant run distance in the first option collectively contribute to the longest runoff time among the choices provided.