A Trial of the Potential Value of Aqualung Diving to Coastal Physiography on British Coasts (original) (raw)
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Sedimentology and Geomorphology of Coasts and Estuaries
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Coastal and nearshore morphology, bedforms and sediment transport pathways at Teignmouth (UK)
Continental shelf …, 2004
The beach and nearshore area of Teignmouth (UK) has been the object of a multidisciplinary research project, COAST3D, carried out by 11 European institutions. This paper emphasises the sedimentological and morphological investigations of the intertidal and nearshore area using a variety of techniques. From the results presented, it is clear that the Teignmouth site is very dynamic. Sediment mobility is high during fair-weather conditions owing to the strong jet-like current flows associated with the presence of the narrow estuary mouth. The beach at Teignmouth can be categorised as composite with a dissipative low-tide terrace and a reflective upper beach. From surficial sediment sampling, selective transport processes were identified, imposed by the high current velocities at the estuary mouth. This process also leads to the formation of characteristic depositional lobes with poorly sorted sediment. From digital sidescan sonar mosaicing, cross-shore and longshore-oriented bedforms could be observed, with their characteristics being dependent on the pre-survey hydro-meteo conditions. Although the nearshore system is dominated by the jet-outflow, littoral drift processes can also be important. They proved to be important for beach morphological changes leading to a rythmic alongshore beach behaviour which was attributed to a reversal of the littoral drift imposed by a period of larger waves. Moreover, the influence of waves and associated longshore currents cannot be neglected as they form the link between different sedimentary environments. From combined side-scan sonar imagery and sediment trend analysis, residual sediment transport directions were identified. These showed that fair-weather and storm-dominated processes are needed to explain the textural and morphological differentiation at this site. Further analysis will be required to identify the different time-scales involved in producing these changes. r
Coastal Morphology, 2018
The coast is shaped by tectonic and structural features, the nature of the rock forming the coast and depositional and erosive activity. The basic type of coast is determined by tectonic and structural factors that have been imprinted during formation of the continents. For example, the Pacific coast of North America has been uplifted, compressed, and received exotic blocks from the sub ducting Pacific Plate. These processes have developed a narrow continental shelf, with mountain ranges blocking river drainage and sediment influx from the continent. In contrast, the Atlantic coast is a divergent margin -the North American crustal plate is moving away from the Atlantic oceanic ridge and the dominant tectonic process has been isotactic subsidence of the continental margin. Greater river discharge carries sediments to the marine environment and a broad coastal plain and wide shelf have resulted.
Tidal Flats, Muddy Seafloors, Sandy Coasts, and Inlets
The long-term goal is to develop field-verified models for the evolution of surface-gravity waves, circulation, sediment transport, and the subsequent morphological response in shallow, coastal waters. OBJECTIVES The objectives of our studies in FY11 were to analyze observations of currents, waves, and bathymetry on tidal flats, and to develop, test, and improve models for tidal-flat processes. Specific goals related to tidal flats were to investigate the relative importance of riverine and tidal flows to the circulation and density stratification. Additional goals in FY11 included developing models for mud-induced dissipation of waves, analyzing waves, currents, and morphological change on sandy beaches, providing ground truth for remote sensing of littoral areas, and planning a study of waves and circulation in the vicinity of a strong, narrow jet of water at an inlet. APPROACH Our approach is to collect field observations to test existing hypotheses, to discover new phenomena, to provide ground truth for remote sensing studies, to initialize and test data assimilative models that invert for bathymetry, and to calibrate, evaluate, and improve models for tidal flat hydrodynamics and morphological evolution and for waves propagating in shallow water across muddy and sandy seafloors.
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Marine Geology, 1999
A set of 125 vibrocores collected on the basis of a dense grid of high and very high resolution seismic coverage over a Ž . tidal sand bank the Middelkerke Bank provides a unique opportunity to reconstruct the stratigraphy and sedimentary facies succession of such a large tidal sand body. Five sedimentary facies are distinguished. They range from clay to pebble and display various types of bedding and lithologies corresponding to different depositional environments. A succession of four Late Quaternary units are defined on the basis of the stratigraphic framework given by the seismic grid. The first unit represents the infill of a palaeovalley system by tidally influenced sedimentary facies. It is followed by extensive and thick lagoonal or sub-tidal deposits. The third unit reveals the development of a landward prograding storm-dominated sand bar. This unit is dominated by clean fine sand. The last unit corresponds to the present-day tidal sand-bank. It shows the typical Ž . offshore tidal sand bank facies cross-bedded sand prograding in an offshore direction. Like other banks located in a more offshore position, the Middelkerke Bank is a composite bank incorporating facies which do not occur in 'classic' tidal sand banks. q . 0025-3227r99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved.