constructive wave

A low-frequency (6-8 per minute) spilling wave, with a long wavelength and a low crest, which runs gently up the slope of the beach. Such waves are thought to deposit material, because the strength of the swash greatly exceeds that of the backwash, which is reduced by percolation. Spilling waves usually occur on gently sloping beaches, and are responsible for the formation of beach ridges and berms.