Morphological Changes of the Ebb-Tidal Delta of the Eastern Scheldt during Recent Decades
Van den Berg, J.H. 1984 Morphological Changes of the Ebb-Tidal Delta of the Eastern Scheldt during Recent Decades. Geologie & Mijnbouw, 63, 363-375.
The delta consists of a complicated system of shifting channels and shoals. From 1959 onwards detailed soundings of... more The delta consists of a complicated system of shifting channels and shoals. From 1959 onwards detailed soundings of the area have been carried out almost yearly and thus the most important morphological changes in the last 25 yr have been established. An attempt has been made to trace the impact of 'Delta-project' constructions which have already been completed upon the trend of the morphological evolution. Attention is paid to implications of this investigation for the study of fossil examples of ebb-tidal deltas. A main conclusion is that a rather small increase in tidal discharge at the entrance of the Eastern Scheldt basin resulted in a remarkable and rapid expansion of the ebb-tidal delta
Download (.pdf) Variation in Ebb-Tidal delta Geometry along the Coast of the Netherlands and the German Bight
Sha, L.P., and Van den Berg, J.H. 1993 Variation in Ebb-Tidal delta Geometry along the Coast of the Netherlands and the German Bight. Journal of Coastal Research, 9, 730-746.
The morphology of the ebb-tidal deltas along the Dutch and German North Sea coast is examined in relation to wave,... more The morphology of the ebb-tidal deltas along the Dutch and German North Sea coast is examined in relation to wave, offshore and inshore tidal regimes. Remarkable differences exist in the shape of shoals and tidal channels in the ebb-tidal deltas along the coast from the SW Netherlands to the German Bight. The large ebb-tidal deltas along the western Wadden Islands have a seaward protruding shape strongly oriented to the left with respect to the offshore direction (or updrift with respect to the direction of the general regional longshore drift). Ebb channels also turn to the left in their most seaward part. On the other hand the ebb-tidal deltas along the southwestern coast of the Netherlands as present before the tidal inlet closures of Delta Project showed a sharp-edged triangular shape pointing landward. Their ebb channels bifurcated seaward, orienting updrift and down- drift on both sides of the ebb-tidal deltas. It is shown that these variations are due to differences in interaction of offshore tidal currents and inshore tidal currents between the two areas. In the original ebb deltas of the SW Netherlands, the ebb channels bifurcating to the left are more pronounced than the channels bifurcating to the right. This is probably related to a significant decrease in tidal range along the coast to the north. In the Wadden Sea the small tidal deltas, in contrast to the large ebb tidal deltas, protrude downdrift. This is due to the large longshore component of wave energy flux relative to the small tidal prisms through the inlets. A descriptive model of ebb-tidal delta geometry is proposed, which considers the relative influence of waves as compared to tidal currents, wave direction and the interaction of offshore and inshore tidal currents.
Ebb-tidal delta deposits along the west Frisian Islands (The Netherlands): process, facies, architecture, and preservation
L.P. Sha & P.L. de Boer (1991)
Clastic Tidal Sedimentology; Can. Soc. Petrol. Geol. Mem. 16, 199-218
The morphologies of the ebb-tidal deltas of Texel, Terschelling and Ameland inlets and the resulting sand transport... more The morphologies of the ebb-tidal deltas of Texel, Terschelling and Ameland inlets and the resulting sand transport patterns are greatly influenced by the interaction of shore-parallel tidal currents with tidal currents through the inlets. These three inlets and their ebb-tidal deltas are similar in many aspects, and together they differ from North American Atlantic coast examples and from those of the East Frisian Islands. Sedimentary facies and sequences, and sand body geometry of these three inlets/ebb-tidal deltas are strongly controlled by this interaction of offshore tidal currents, tidal currents through the inlets, and waves. The interaction and relative strength of both tidal current systems determine the flow patterns and and orientations of the main ebb channels in the ebb-tidal deltas. Different orientations of (asymmetrical) ebb-tidal deltas as compared to those along the East Frisian Islands and the U.S. east coast, as well as a change of the general orientation of the main ebb channel of the ebb-tidal delta of Texel Inlet since the 16th century, are related to differences and changes in the relative importance of tidal currents and waves. Waves and longshore drift tend to force the ebb-tidal delta into an updrift asymmetry. Under the present regime of waves and longshore drift in this area, the critical boundary between updrift and downdrift asymmetry appears to be at a tidal prism on the order of 500 . 10^6 m^3. The volume of ebb-tidal delta sand bodies is approximately 1 km^3 (Texel), a considerable part of which can be preserved in the fossil record. Holocene deposits off the West Frisian Islands indeed show that preservation of ebb-tidal delta deposits during a rise of relative sea level is possible under certain conditions. The strength of tidal influence is of great importance for for determining both the basal boundary and the seaward extent of the ebb-tidal delta systems. Thus, it is inferred that preservation potential of ebb-tidal delta deposits can be positively correlated with the relative dominance of ebb-tides during their formation.
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