Beaches and coastal dunes are dynamic geomorphic systems that respond to process forcing over a broad spectrum of spatial and temporal scales. At all scales, there are potential suites of interaction between system forms and processes, and the mechanisms of interaction are stressed in this article. At micro-scales, this interaction is formalized through the concept of morphodynamics, and deterministic and probabilistic approaches are used to model sediment transport and landform development over time scales of hours to months and space scales of metres to kilometres. Meso-scale interactions are conceptualized using a sediment-budget approach. Nine characteristic environments comprise the beach and dune sediment-budget ensemble, representing a classification scheme for reciprocating coastal systems.Beaches and coastal dunes are among the most dynamic of geomorphic environments. Energy expenditures from waves, currents and winds are typically large and applied over relatively small areas. Form changes are frequent, often with dramatic fluctuations over timescales of hours to days, making these environments promising venues for studies of process-form relationships. Form changes also occur over periods of decades and longerimportant timespans for coastal resource management and the study of landscape evolution.Traditionally, the wave-current-dominated beach and the wind-dominated dunes have been examined as distinct and separate systems. During the last decade, however, there has been increased emphasis on 'beach-dune interaction' (e.g., Short and Hesp, 1982;McLachlan, 1990;Psuty, 1988; with the recognition that these two environments are often strongly coupled and mutually adjusted. Sediment exchanges between beach and dune environments are governed by complex feedback mechanisms that may have important repercussions for the evolution of the integrated beach-dune system (Chapman, 1989). Such a holistic perspective has been adopted by coastal resource managers for quite some time (e.g., Walker, 1990), but it is relatively recent to coastal engineering and geomorphology. This article is a review and discussion of literature that pertains to the notion of beach-dune interaction with particular focus on process-form coupling -that is, processes that affect and are affected by local morphology. Downloaded from 414 11 Conceptual framework and scope ~ &dquo;... Our discussion of beach-dune interaction is organized around a conceptual framework (Figure 1) based on Valentin's (1952) classification method. In this scheme, coastal change can be in response to relative displacement of the water-land interface through either horizontal or vertical movement of the water level or the land mass over a spectrum of spatiotemporal scales. Two end-member situations can be identified: (1) unconditionally advancing coasts, where depositional processes and/or emergent trends create a situation where the shoreline migrates seaward; and (2) unconditionally retreating coasts, where erosional processes and/or submergent trends cause shorelin...