CIV E 445-APPLIED HYDROLOGY
SPRING 2005
SECOND MIDTERM
APRIL 11, 2005, 1400-1515

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. (30%) An overland flow plane has the following characteristics:

    plane length L = 50 m;
    plane slope So = 0.007;
    Manning's n = 0.06;
    rainfall excess i = 45 mm/hr.

    Determine if the kinematic wave approximation is applicable to this set of overland flow conditions.

  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).

    Effective rainfall (cm/hr):    2.0   3.0
    Total rainfall (cm):              6.0   9.0

  3. (40%) Please answer briefly:

    1. Why is the rational method referred to as "rational"?
    2. What are the five variables in the theoretical time-of-concentration formulas?
    3. What are the four explicit variables (or parameters) in the runoff curve number methodology?
    4. Why does the Snyder synthetic unit hydrograph apply for larger basins than the SCS synthetic unit hydrograph?
    5. What is the standard peak rate factor (PRF) in the SCS unit hydrograph methodology?
    6. Which SCS Type storm is the most intense? Where is it applicable?
    7. Why is the TR-55 method physically consistent?
    8. According to the Gumbel method, what is the return period of the mean annual flood?