Collective Movement of Sediment in Littoral Environment

Collective movements of sediment occur in the form of sand waves in the nearshore zone and affect beach topography to a significant extent. Bar-type sand waves move only in the onshore direction and account for various accretive profiles on the subaerial beach. When the beach is eroded, these sand waves are simply disintegrated on the subaerial beach, instead of migrating back in the form of sand waves. These characteristics of bar-type sand waves help explain dynamic behavior of beach profiles with respect to profile configuration, sediment storage, and beach width. Cusp-type sand waves are considered to be a product of interaction between longshore currents and an erodible bed. Their presence causes variability in beach profiles along the shore between those containing a prominent bar and those without a bar. Migration of these sand waves may well produce pulsational transfer of material along the shore.