During storm events, what happens to the grain size on the beach and why?

• A. Increases because finer sand is transported offshore
• B. Decreases because coarser sand is deposited
• C. Remains unchanged
• D. Becomes mixed with heavier minerals

Answer: (A)

Storm energy sorts sediment by size: stronger waves push finer grains away and leave coarser material behind. Finer grains have lower settling velocities and are easier to entrain and transport offshore or into deeper water, while heavier, coarser grains resist movement and stay on the beach. As a result, the surface grain size on the beach becomes coarser on average after a storm. This winnowing effect explains why the beach grain size increases when finer sand is carried offshore. Shorter-term deviations might occur as fines are deposited elsewhere or backwash reworks material, but the dominant pattern during storm events is a coarser beach surface due to selective removal of fines.