CIV E 445-APPLIED HYDROLOGY
SPRING 2008
SECOND MIDTERM
APRIL 9, 2008, 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 80-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:

    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, defined at two 3-hr increments (6-hr total event duration).

    Time (hr):                               3      6
    Effective rainfall (cm/hr):          2.0   4.0
    Total rainfall (cm):                   6.0  12.0

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

    1. What distinguishes a small catchment from a midsize catchment from a hydrologic standpoint?
    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 most intense? Where is it applicable?
    6. How does the TR-55 method emulate Creager's formula? Be explicit. Is the Earth as rough as an ping-pong ball or an orange?
    7. What is the return period of the mean annual flood?
    8. What is the range of variation of the correlation coefficient ρ? What does ρ = 0 mean?
    9. What is the range of return periods used in hydrologic design?
    10. How will global warming affect urban drainage design? Be explicit.