Question

short answers

1. T          F          When using the runoff coefficient, c, the Rational Method assumes that land uses are uniformly distributed within a drainage area.

2. What is the overland flow travel time for a hydraulic path 140 ft long through dense grass at an average slope of 1.0%?

1. 1 minute

2. 4 minutes

3. 21 minutes

4. 25 minutes

3. The rational method assumes rainfall duration equal to the time of concentration. If an estimated time of concentration is larger than the actual time of concentration for the drainage area, the peak runoff determined will be (greater than, equal to, less than) the actual peak discharge.

4. T          F          A storm with a return period of 25 years will occur only once every 25 years.

5. A drainage basin’s “time of concentration” means the time

1. the time for the first raindrop to flow down the steepest slope in the area.
2. the time to drain the drainage area after the rain stops.
3. the longest time of flow to the point of interest.
4. the time that is equal to the duration of the rainfall event.

6. (12 pts) The three general types of flow that could occur along the hydraulic path in a drainage area are ______________________________ flow, ______________________________flow, and ______________________________ flow.

7. The average rainfall rate in inches/hour is called the

1. duration.
2. return period.
3. frequency.
4. intensity.

8. A drainage basin is defined as the

1. boundary separating two adjacent rainfall collection basins.
2. surface preventing infiltration of water into the soil.
3. land surface having similar characteristics with a single outflow point.
4. continental divide.

9. What is the shallow concentrated flow travel time for a hydraulic path 540 ft long through average grass at an average slope of 3.4%?

1. 179 minutes
2. 18 minutes
3. 4 minutes
4. 3 minutes

10. What is the channel flow travel time for a hydraulic path 2000 ft long and a velocity of 9.52 ft/sec?

1. 3.5 minutes
2. 5.3 minutes
3. 21 minutes
4. 210 minutes

Answer 1