CETN IV-18
March 1999
Example 1: Scour at Ventura Harbor, California. During storm conditions, longshore
currents flowing through a narrow gap between the North Jetty and Detached Breakwater at
Ventura Harbor caused a scour hole with maximum depth of 9.5 m below mean lower low water
(mllw). Figure 4 shows a plan view of the navigation structures. The scour hole was filled with
quarrystone and protected with a stone sill having top elevation at -4.5 m mllw (Hughes and
Schwichtenberg 1998). The sand in the vicinity is quartz with a median grain size near de =
0.2 mm (or de = 0.0002 m).
Figure 4. Ventura Harbor, California, navigation structures
An estimate of the equilibrium discharge per unit width corresponding to a scour depth of 9.5 m
is determined from Equation 6 using a grain size of 0.2 mm, i.e.,
[(
) (2.65 - 1)] (0.0002 m ) (9.5 m )
1/ 2
3/8
9/8
q e = 5.12 9.807 m / s 2
= 10.63 m 2 / s
8
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