CIV E 445-APPLIED HYDROLOGY
FALL 2008
SECOND MIDTERM
NOVEMBER 10, 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 70-ha watershed with a rainfall intensity of 20 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 13
    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 is the kinematic shock?
    4. What are the four explicit variables (or parameters) in the runoff curve number methodology?
    5. What is the value of PRF (peak rate factor) used in the NRCS unit hydrograph? Where does it come from?
    6. Which NRCS type storm (I, IA, II, or III) is the most intense? Where is it applicable?
    7. How does the TR-55 method emulate Creager's formula?
    8. According to Gumbel, what is the return period of the mean annual flood?
    9. What is the range of variation of the correlation coefficient ρ? What does ρ = 0 mean?
    10. What is the range of return periods used in hydrologic design?