CIV E 445 - APPLIED HYDROLOGY
SPRING 2014
LAB No. 5 SOLUTION

    • The major rivers and creeks in San Diego County, draining into the Pacific Ocean, from north to south, are:

      • Santa Margarita

      • San Luis Rey

      • Escondido Creek

      • San Dieguito River

      • Los Penasquitos Creek

      • San Diego River

      • Sweetwater River

      • Otay River

      • Tijuana River.

    • The maximum average annual rainfall in San Diego County is 30 in. It occurs along the highest peaks in the mountains.

    • The minimum average annual rainfall in San Diego County is 3 in. It occurs in the eastern desert, in the Salton Sea basin.

    • From Fig. 3-1: 3.35 in/hr. From the Equation: 3.32 in/hr.

    • From Table 3-1, for soil type C and 80% imperviousness: C = 0.78.

    • From Fig. 3-3, for a watercourse distance of 100 ft, slope 1%, and C = 0.55, the overland flow time is 10 minutes. From the formula, the overland flow time is 9.9 minutes.

    • From the formula: Tc = 0.56 hr = 33.8 minutes. From the chart (Fig. 3-4): Tc = 33 minutes. From the calculator: Tc = 33.77 minutes.

    • From Fig. 3-6: flow depth y = 0.4 ft; flow velocity V = 4fps.

  2. The theoretical peak outflow is:

    Qp = I A = 2 cm/hr × 18 ha × 10,000 m2/ha × 0.01 m/cm / (3,600 s/hr) = 1 m3s

    Table 1 shows the results of time of concentration.

    Slope
    (planes and channel)         		Tc
    (hr)
    0.01 2
    0.005 3
    0.002 4
    0.001 5
    0.0005 8

    It is concluded that the time of concentration is inversely proportional to the slope.