CIV E 445 - APPLIED HYDROLOGY
SPRING 2014
LAB No. 9 SOLUTION

  1. The correlation coefficient of the joint distribution of quarterly flows is:

    rx,y = 0.681.

  2. α = 42.46643; β1 = 0.015533; β2 = -1830.40.

    y = α + β1 x1 + β2 x2

    tc = α + β1 L + β2 S

    tc = 42.46643 + (0.015533 × 2384) - (1830.40 × 0.0011)

    tc = 42.46643 + 37.030672 - 2.01344 = 77.48 minutes.

  3. Running CREAGER, we find that the flood discharge is likely to vary from 193,289 to 644,297 cfs. So the maximum flood discharge is 645,000 cfs. The service spillway capacity is rated at 250,000 cfs (Wikipedia). If the emergency spillway can pass the difference (645,000 - 250,000 = 395,000 cfs), then the spillway system is properly designed.

    Service spillway
    Emergency spillway

  4. The drainage area of Penasquitos Creek is 42.1 sq mi. The mean annual precptation in Poway (from the given map) is 14 in.

    The 100-yr flood discharge according to the USGS flood-frequency 1977 report is:  6,045.72 cfs.

    The 100-yr flood discharge according to the USGS flood-frequency 2012 report is:  6,101.73 cfs.