CIV E 445-APPLIED HYDROLOGY
SPRING 2009
SECOND MIDTERM
APRIL 13, 2009, 0730-0845

Name: _______________________ Red ID _________________ Grade: _______

Instructions: Closed book, closed notes. Use engineering paper. When you are finished, staple your work in sequence (1 to 3), and return this sheet with your work.

  1. (20%) What is the peak discharge for a 60-ha watershed with a rainfall intensity of 30 mm/hr, if the entire watershed is paved. Assume C= 0.95.

  2. (30%) A certain basin has the following 2-hr unit hydrograph (1 cm of rainfall), defined at hourly ordinates:

    Cumulative time (hr)0 1 2 3 4 5 6 7 8 9 10 11 12 0
    Flow (m3/s)0 5 15 30 60 70 60 55 45 35 25 15 5 0

    Calculate the flood hydrograph for the following effective storm pattern:

    Time (hr) 0-33-6
    Effective rainfall (cm/hr)24
    Effective rainfall (cm)612

  3. (50%) Please answer in a brief statement:

    1. What is the upper size limit (in square miles) for a small catchment?
    2. Why is the rational method rational?
    3. What are the four explicit variables (or parameters) in the runoff curve number methodology?
    4. What is the value of PRF (peak rate factor) used in the NRCS unit hydrograph? Where does it come from?
    5. Which NRCS type storm (I, IA, II, or III) is the least intense? Where is it applicable?
    6. According to Gumbel, what is the return period of the mean annual flood?
    7. What caused the June 1983 flood on the Colorado River?
    8. What caused the damage of the Glen Canyon tunnel spillway? How did USBR repaired it?
    9. What are the advantages and disadvantages of levees?
    10. Why is flood control out of fashion?