Changes on barriers and spits enclosing coastal lagoons

Coastal lagoons have formed where marine inlets or embayments have become partly or wholly enclosed by depositional spits and barriers, built up as a sequel to the world-wide Holocene marine transgression. Spits and barriers consist of sediment (sand, shingle) derived from the sea floor or carrier alongshore from river mouth or eroding cliff sources; they have been shaped primarily by wave action, some migrating landward while others have remained in position or prograded seaward. A modern prevalence of erosion on barrier coastlines, recession resulting from net losses of sediment offshore, alongshore, or landward has been deomonstrated. This is the outcome partly of rising sea level and partly of diminishing sediment supply. Often the consequence of man's impacts on coastal environments. Examples are given of changes that have resulted from the cutting of artificial entrances through barriers to the building of barriers across tidal inlets to exclude marine penetration

Regional sea level, Southern Oscillation and beach change, New South Wales, Australia

Coastal erosion is a problem of increasing concern that affects 60% of the world\u27s sandy coastline. This erosion has been attributed to increased storminess, tectonic subsidence, eustatic sea-level rise, decreased shoreward sediment movement from the shelf, permanent longshore leakage of sediment from beach compartments, shifts in global pressure belts resulting in changes in the directional component of wave climates, and human interference. No one explanation has worldwide applicability because all factors vary in importance regionally. Evaluation of factors is complicated by a lack of accurate, continuous, long-term erosional data. Historical map evidence spanning 100-1,000 yr has been used in a few isolated areas; however, temporal resolution has not been sufficient to evaluate the effect of climatic variables. Air photographic evidence is restricted to the past 40 yr, and often suffers from insufficient ground control for accurate mapping over time. Ground surveying of beaches was rarely carried out before 1960 and is often discontinuous in time and space. I have resolved the problems of temporal and spatial continuity by studying change for the whole of Stanwell Park beach, New South Wales, Australia for the period 1895-1980 (Fig. 1). I report here that using the average high-tide wave run-up position measured accurate to ±2.5 m from oblique and vertical photographs, changes could be linked to regional sea-level variation and a globally significant climatic variable, the Southern Oscillation (SO)