Coastal sand islands with high dunes usually contain one or more unconfined, unconsolidated sedimentary aquifers, where groundwater is stored and transmitted through inter-granular voids between sand particles. These unconsolidated sedimentary aquifers may be perched due to the presence of low permeability layers within the coastal sand mass (e.g. layers of coffee rock or beach rock). Examples of coastal sand islands with high dunes along the Queensland coast include Fraser, Moreton and North Stradbroke islands.

A wide range of ecosystems may depend on groundwater in these unconsolidated sedimentary aquifers to support their plant and animal communities, ecological processes and delivery of ecosystem services.

• Palustrine (e.g. swamps) and lacustrine (e.g. lakes) wetlands and riverine (e.g. streams and rivers) water bodies on coastal sand masses may depend on the surface expression of groundwater from these unconsolidated sedimentary aquifers. In general, the regional aquifer sustains stream flow in lower parts of the landscape and perched aquifers may supplement streams higher in the landscape.
• Terrestrial vegetation on coastal sand masses, usually in lower parts of the landscape or at low altitudes, may depend on the sub-surface presence of groundwater in these sand mass aquifers where groundwater is typically accessed through the capillary zone above the water table.
• Unconsolidated sedimentary aquifers may also support subterranean ecosystems within the aquifer itself, which sometimes is indicated by the presence of stygofauna.
• Estuarine and near-shore marine ecosystems located adjacent to coastal sand masses may depend on the discharge of groundwater from these unconsolidated sedimentary aquifers.

Pictorial conceptual model PDF

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