Beach Ridges as Favored Locales for Human Settlement on Pacific Islands

Abstract

Coastal beach ridges have been favored locales for human habitations on Pacific islands since initial human settlement. Their smooth crests shaped by surf action form sandy substrates that differ in morphology from eolian dunes. Island beach ridges that were accreted to island cores during post‐mid‐Holocene drawdown in regional hydro‐isostatic sea level include coastal spits that partially enclose backbeach wetlands, tombolos that tie previously separate islets together, and cheniers that form elongate elevated tracts on accretionary coastal plains. Some beach ridges were accreted directly to the flanks of bedrock islands, but others grew at varying distances from ancestral bedrock shorelines to trap remnants of offshore lagoons as lakes or swamps and marshes between the beach ridges and exposures of island bedrock. Composite chenier plains formed by the successive lateral accretion of multiple beach ridges over time are prominent locally as broad coastal lowlands. Longshore sand transport driven by prevailing trade winds influences beach ridge evolution but beach dynamics reflected by beach sand textures confirm the dominance of onshore sand movement from wave attack for the morphology of the beach ridges.