Figure 4: Model (upper) and prototype (lower) scour hole contours.
Scour contours measured in the model downstream of the rock sill are shown in
the sketch of Figure 5. Contour values correspond to prototype depths in meters.
The scour hole attained a depth greater than the scour that occurred in the second
calibration test as shown in the upper sketch of Figure 4. Besides being displaced
downstream of the sill, the scour hole was narrower and more elongated than scour
that occurred without the rock sill in place. Where the scour hole impinged on the
breakwater toe, armor stones became unstable and fell into the scour hole.
The model test of the existing Ventura configuration strongly supported the hy-
pothesis that current-induced scour at Ventura Harbor had the potential to undermine
the leeside armor slope along the entire length of the detached breakwater south of
the rock sill. This would cause considerable damage to the leeside armor slope, and
expensive repairs would be needed. Therefore, construction of a protective toe berm
along the detached breakwater was warranted. In the following discussion, all stated
values are in prototype units.