Nearshore-surfzone system limits and the impacts of sand extraction

摘要: Nearshore coastal sand mining may adversely affect development where extractions occur within the active beach-nearshore system. In this paper outer limits of system are reviewed, with inclusion new data from Pakiri, New Zealand. These include interpretation nearshore sedimentology, morphology, bedforms and benthic fauna, theoretical estimates sediment movement, historic evidence morphodynamics, measurement seaward extent riphcad plumes during or following storm wave conditions, stratigraphic indications seabed erosion deposition. There is convergent that for east coast Australian Zealand moderate to high energy beaches, including maximum limit modern occurs around 25 m isobath. Recent interpretations geomorphology Pakiri-Mangawhai system, which shallow marine takes place, re-examined in light results review. The conclusion substantial onshore exchange between inner shelf environments, therefore open inputs, not sustained. investigations bedforms, subtidal facies, morphodynamics transport thresholds, indicates nearshore-inner boundary approximates isobath at Pakiri. Significant does beyond depth over relevant time scales. A re-analysis beach profile records, as well barrier morphostratigraphy, that, contrary most previous interpretations, shows no strong accretionary trend, best stable possibly erosional. We hypothesize weak recovery severe 1978 be a consequence mining. context entails risk affecting processes landforms.