A chenier is a beach ridge resting on silty deposits which has become isolated from the shore by a band of tidal mudflats. A chenier plain consists of a series of cheniers separated by mudflats.
The Miranda-Kaiaua cheniers are first formed as sand and cockle-shell bars on the foreshore or intertidal flats. The bars are then moved landward by wave action. Eventually the bars attain sufficient height to withstand such wave action. Deposition of fine sediments also occurs in the embayment created on the landward side of the shell ridge. These sediments accumulate to such an elevation that mangroves and other saltmarsh plant species can colonize the area. Their stabilising roots assist in the accumulation of mud and a process of natural reclamation occurs, thus building up the plain.