A newly-completed city engineering project is designed to regulate high summer water levels in the lower river lagoon, caused by the annual sand buildup that blocks the rivermouth. It will do that by pumping backed-up lagoon water past the blockage and out to the beach through a 24" culvert (top photo) whenever it rises above a certain level. That level is low enough to prevent flooding, but high enough to protect the lagoon habitat for its inhabitants. The outflow water will presumably stop being so rusty once the culvert rinses out.
The lower photo shows the construction scene shortly before completion. The culvert is the bright horizontal line in the middle distance, below the bluffs.
