Freshwater wetlands on coastal floodplains on the Northern Beaches occur in swampy, saline, alluvial soils around the margins of estuaries and coastal lagoons. They are associated with coastal areas subject to periodic flooding and in which standing freshwater persists for at least part or most of the year. These areas are usually landward side of the Saltmarsh community when the two occur together.

These areas may include Estuarine Reedland, Estuarine Paperbark Scrub and Swamp Oak Forest which are dominated by dense reedland including Phragmites australis (Common Reed), Baumea Juncea, Juncus kraussii and samolus repens. Estuarine Paperbark Scrub which mainly occurs at Dee Why Lagoon  is dominated by stands of Melaleuca ericifolia with an understorey of reedland and Swamp Oak Forests occur around the four lagoons, Narrabeen, Dee Why, Manly and Curl Curl and around areas of Pittwater.