How Constructive Waves Build Beaches: Sediment Transport & Deposition

Constructive waves—low-energy, long-period waves—build beaches by moving sediment onshore. The process:

1. Oblique approach: Waves arrive at an angle, carrying sand alongshore and onshore.
2. Breaking & suspension: Gentle spilling breakers stir sediment into the water column.
3. Onshore transport: Swash (uprush) pushes sediment up the beach; weak backwash can't pull it all back.
4. Net deposition: Sand accumulates → beach widens, berm builds, profile steepens.
5. Longshore drift contribution: Angled waves also move sediment alongshore, feeding adjacent beaches, spits, bars.

Constructive waves dominate in fair weather; destructive (storm) waves erode. The balance shapes long-term beach morphology.