Remaining Capacity of Low-Crested Rubble Mounds Damaged by Breaking Waves in Surf Zone

Abstract

The rehabilitation timing of a damaged rubble mound structure depends on the remaining capacity of the deteriorated structure. A laboratory experiment was conducted in a wave flume to measure the remaining capacity of a low-crested rubble mound inside the surf zone on a sand beach. The formation of a bar and trough feature modified wave conditions at the toe of the structure. Wave transmission over and through the structure increased with lowering of the mound crest. The mound with a double armor layer on smaller core stones was exposed to irregular wave action lasting 22.2 h. Some of the core stone was visible through holes of the thinned armor layer but remained in place. Crest lowering reduced the wave action on the damaged mound. On the other hand, the mound with a single armor layer did not stabilize itself because of core stone removal after 7.8 h. The rubble mound structure was resilient as long as the core stone was protected.