Why is sediment supply important for the growth of coastal dunes?

Sediment supply is the primary limiting factor in the development and growth of coastal dunes.1

Dunes form when wind transports sediment from the beach in a landward direction, depositing it wherever an obstruction hinders further movement. The availability of this sediment determines the scale of the dunes; regions with a consistent and abundant supply can support large dune systems, while areas with limited supply often feature only small, isolated accumulations.1

The process of dune growth is essential for the progradation of a coast, meaning the land grows seaward. Small wind-shadow dunes, or coppice mounds, initially form on the backshore of the beach. If the sediment supply remains steady and the dunes are not destroyed by erosion, these mounds can develop into foredunes, which serve as the seaward-most line of coastal dunes. Consequently, the presence of parallel dune ridges on many barrier-island or strand-plain coasts serves as a direct testament to this ongoing process of sediment-driven growth.1