1. Preciptation

16. There are two issues to consider here; the peak amount and the time to peak. In case “a”, we need more time for runoff to arrive at the outlet thus compared to “b” it will need more time and thus delay in peak. In case “c”, the outlet drains larger are at a shorter time, which leads to a less time to peak.

20. Assume Runoff Coefficient is 0.42

21. Solution
Storm intensity for a duration of 1.5 hours (time of concentration) and frequency of 50 years, is obtained from the IDF curve as approximately 2.2 mm/hr.
Q= CxIxA
= 0.42 x 2.2 x 71 x 10-3x104= 656 m3/hr

22. Example

25. Homework
Annual measurements of rainfall and runoff for a certain watershed were summarized in the table below. Under this scenario, answer the following:
1- Develop a linear relationship between rainfall and runoff.
2-Find out the minimum annual rainfall necessary to produce runoff for this watershed.
3- What would be the runoff for an annual rainfall of 950 mm?

26. Determine the drainage density of the basin shown below
Determine the drainage density of the basin shown below . Area of the basin is equal to 6400 hectares. All the streams length in kilometers.

27. You have the following four cases of runoff hydrographs for four situations. Justify the different shape-looking hydrographs. Consider “a” versus “b” and “c” versus “d”