in this case, a sand spit has formed off the end of this breakwater.wave tank shows how the sand spit built up. the waves strike the breakwater at an angle and bend around it into the harbor. when sand is added, the waves carry it into the harbor, where it builds into a spit behind the breakwater. to prevent the harbor from being sealed off and the beach beyond from being deprived of sand, engineers installed a dredge to pump the sand back into the longshore current by picking it up in the harbor and dumping it further down the coast. not only do beaches change continuously as sand is moved through them by the longshore current, but seasonal changes occur as well. the beaches change from season to season. by summertime, the waves are fairly low and gentle, and that has a tendency to drag sand towards the beach and build up the beach and make it broader, wider, and as it piles up, the sand has a fairly gentle slope. in the wintertime, though, the larger waves, more energetic waves, pick up that sand, tend to move it offshore, and store it in large sand