How do coastal dunes form behind beaches?

Coastal dunes form immediately landward of the beach through the transport and deposition of sediment by wind. As wind carries sand from the beach in a landward direction, the accumulation process begins whenever an obstruction hinders further transport.1

The development of these dunes typically follows a specific progression:

• Initial Accumulation: Small wind-shadow dunes, known as coppice mounds, form on the backshore of the beach.1
• Growth: If there is a consistent supply of sediment and the mounds are not destroyed by erosion, they evolve into foredunes, which represent the seaward-most line of coastal dunes.1
• Stabilization: Various grasses and vines often colonize the dune surface, helping to stabilize the sand.1

The primary limiting factor in the size and development of these dunes is the available sediment supply. While most coastal dune sand is composed of quartz, it often contains a greater mixture of other minerals compared to dunes found in continental interiors.12