This thesis examines the coastal system of Gore Bay, North Canterbury, New Zealand. The coastal environment at Gore Bay has not previously been studied in depth and is poorly understood. Effective management of any coastal area requires a thorough description of the entire system, including processes, sediments and morphology. Wind and wave observations, beach profiles, sedimentary analysis, photographic evidence and archival data were used to investigate these three components and unravel the complex relationships within the Gore Bay coastal system. Gore Bay is approximately four kilometres long and comprises a mixture of both sand and gravel sized sediments. The bay is partially exposed to a high energy swell environment, with the southern end sheltered from the prevailing southerly waves. Two discrete sediment populations were identified in Gore Bay: a pebble mode at around -50 (32mm) and a sand mode at approximately +20 (0.25mm). The proportion of sand generally decreases toward the north of Gore Bay, however there is significant temporal variation in sand distribution. Average beach slope is 3.1° in the south, increasing to 8.8° due to a reduction in beach width and increase in beach height toward the north of the bay. These alongshore variations are related to the degree of exposure to the wave environment, which is more sheltered to the south. The beach in the south is backed by a scarp cut into an ancient dune field, on which the village of Gore Bay has been developed. In the north, the backshore slopes landward onto a washover surface and coastal plain, which has an ancient dune field on its landward side. The morphological response of the beach is dependent on both the characteristics of the wave environment and the distribution of sediments along Gore Bay. The sand and gravel components of the system respond separately to the process environment. Sand moves on- and off- shore as it would on a pure sand beach, while the response of the gravel is dependent upon the permeability of the beach. Beach permeability is affected by grain size, sorting and swash-backwash interactions. Due to the alongshore variation in sedimentary characteristics, the south and north of the bay respond differently to changes in wave conditions. A model of the morphodynamic behaviour of Gore Bay is presented, which takes into account the spatial and temporal variations in beach response. Gore Bay is a transitional sand and gravel beach, which shows significant variation in morphodynamics to the typical mixed sand and gravel beaches described in the published literature. The presence of a wide surf zone and the onshore-offshore cycling of sediment mean that transitional sand and gravel beaches are a discrete beach type. Management of Gore Bay therefore requires site specific investigation rather than the application of "text-book" coastal principles.