Wave Refraction

Wave refraction is the bending of wave crests as they enter water of changing depth, caused by the part of the crest in shallower water slowing while the part in deeper water keeps speed. By the same Snell’s-law geometry as optics, crests turn to become more parallel to the depth contours, so waves approaching a beach at an angle swing toward shore-normal. Refraction concentrates wave energy on headlands and submarine ridges (convergence) and spreads it in bays and over canyons (divergence), setting the alongshore pattern of wave height. The refraction coefficient enters the shoaling calculation that predicts nearshore wave height for design and navigation.