Abstract

Rhomboidal lattice structure is a common feature on sand beaches. It results from the intersection of two sets of small grooves that trend diagonally along the beach slope and forms immediately after or during the last stages of backwash flow.The size of the grooves increases with grain size and proximity to the surf zone. The acute angle of groove intersection is bisected by the direction of beach slope and is variable between about 30° and 45 °depending on a number of factors including: beach width, beach slope, position on beach, and grain size.The grooves are probably the surface expression of planar zones of high shear stress in which the grains become more closely packed that elsewhere in the beach sand.According to this hypothesis, the shear stresses develop due to suction generated as the pore water drains into the sand.

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