Breakwater Stability Study, Imperial Beach, California; Hydraulic Model Model Investigation.

A hydraulic model investigation was conducted at a geometrically undistorted scale of 1:16, model to prototype, to design stable rubble-mound breakwater sections to protect a beach nourishment area at Imperial Beach, California. Both the -5.0 ft mllw contour (shallow-water location) and -10.0 ft mllw contour (deeper water location) were given as proposed construction sites. Twenty-one plans were tested, resulting in two adequate breakwater designs for each of the two proposed sites. A constant high-sill structure, using 3-ton graded armor stone, and an alternating high- and low-sill structure, using 5- and 0.5-ton armor stone, were stable for the design conditions at the shallow-water location. Two alternating high- and low-sill structures proved adequate for the design condition at the deeper wate location. One used 5- and 3-ton graded armor stone on the breakwater trunks and 7-ton capstone on the ends of the breakwater system on 1V-on-3H side slopes while the other design used truck sections of 7- and 5-ton graded armor stone on 1V-on-2H side slopes and 7-ton capstone on the head section with 1V-on-3H side slopes. (Author)