CIV E 530 - OPEN CHANNEL HYDRAULICS
FALL 2010
FIRST MIDTERM
OCTOBER 4, 2010, 1600-1715

Name: _______________ Red ID _________________ Grade: _________

Instructions: Closed book, closed notes. Use engineering paper. When you are finished, staple your work in sequence (1 to 5), and return this sheet with your work.


  1. (20%) A high overflow spillway has a downstream slope of 0.6 H to 1 V. The friction factor of smooth concrete (1/8 of Darcy-Weisbach) is f = 0.004. What is the prevailing Froude number? [Hint: use So = fF2]

  2. (20%) On July 31, 1976, the Big Thompson river, near Loveland, Colorado, experienced a record flood event. Provide a quick estimate of the flow depth (m) and velocity (m/s). Assume critical flow and q = 50 m2/s.

  3. (20%) The overflow spillway at Turner reservoir, in San Diego County, is 8 ft wide. On February 24, 2005, after several days of heavy rain, the head over the spillway was 3 in. What is your best estimate of the discharge?

  4. (20%) What is the discharge in a rectangular channel of bottom width b = 6 m, bed slope So = 0.003, Manning's n= 0.015, and flow depth y = 1 m?

  5. (20%) Please answer the following questions in a brief statement.

    • Why is unsteady uniform flow not possible in practice?

    • What width/depth ratio will assure hydraulically wide conditions in an open channel?

    • Why is it improper to refer to Manning's n as a constant?

    • What is the minimum value of Froude number to avoid channel clogging with sediment?

    • What is the minimum value of Manning n according to Chow? To what surface material does it correspond?