Constructive waves build beaches. These waves are more common in summer than in winter. Constructive waves predominate in calmer weather conditions when less energy is being transferred to the water. Each wave is low. As the wave breaks it carries material up the beach in its swash. The beach material will then be deposited as the backwash soaks into the sand or slowly drains away. When the next wave breaks its swash will deposit more material without it being ‘captured’ by the backwash of the preceding wave.
Constructive waves have a long wavelength and a low-frequency (8– 10 waves per minute). They have a low wave height (typically under 1 metre). The wavefront is gently sloping and gains a little height, breaks and spills onto the beach. Water spreads a long way up the gently sloping beach.
Constructive waves are typically found in sheltered bays and spits where they build up sandy beaches. The image below shows a sandy beach that has formed in Man of War Bay on the Dorset coast.
Man of War Bay
The video below shows constructive waves at Mappleton, Holderness Coast.