This series was photographed while a small group of American Avocet searched a large marsh. The water was lower than usual.
Water flow is controlled here by opening, and closing, wooden trunks (water gates). Nearby were parts for new wood frames. I assume the lower water was to make repairs easier.
The trunk system out in this area has been in use for a few hundred years. All along the coast were rice fields, this area must have fed those fields.