De Belgische strand- en duinformaties in het kader van de geomorfologie der zuidoostelijke Noordzeekust
Depuydt, F. (1972). De Belgische strand- en duinformaties in het kader van de geomorfologie der zuidoostelijke Noordzeekust. Koninklijke Academie voor Wetenschappen, Letteren en Schone Kunsten van België: Brussel. 228, 7 maps pp.
|
|
| Keywords |
Coastal dunes
De kust
Earth sciences > Geology > Geomorphology > Coastal morphology
Earth sciences > Geology > Geomorphology > Coastal morphology > Beach morphology
Ecologische geschiedenis > Natuurgebieden
Geschiedenis culturele leven > Wetenschappen
Sociale geschiedenis > Platteland
ANE, Belgium, Belgian Coast [Marine Regions]; Belgium, Het Zwin natuurreservaat
Marine/Coastal; Brackish water |
| Abstract |
The study of "Belgian beach- and dune-formation in the framework of the geomorphology on the south-eastern North Sea coast", tries to find an explanation for the micro- and macro-morphology of the sandcoast in general, and to give an insight in the genesis of the Belgian coast-dunes in particular . The problems (both static and dynamic coastmorphology) are studied with the help of terrain-observations, amplified with map-analysis and the study of historical documents, as well as with the help of sedimentological analyses. Chapter one of the "Morphological analysis of beach and dune" (part I) deals with the micro-forms of the Belgian and northern French coast (north-east of Sangatte -cf. map 1 and 4 in annex) which were then compared with those of the remaining northern coasts up to Skagen (northern-most point of Jutland in Denmark). The startingpoint for this analysis is the beach- and dune-strip of the Westhoek (between De Panne and the French-Belgian border -cf. map 2), which is the most developed dune-strip of the analyzed French-Belgian coast and which was already dealt with in a previous study (F. Depuydt, 1967). Concerning the beach, the ultimate small and large values of its slope and its width are to be found along the Belgian and northern French coast, where the differences in tide are also largest (more than 4 rn). The width of the beach (between low-tide and high-tide) varies from about 200 m to 1500 m and this under a global angle of inclination of 2 % to 0,32 % with an average value that is less than 1 % for northern France. Locally the greatest part of the side-face of the beach has a beach-angle which doesn't even reach 0,15 % (mostly westward of Dunkirk). Due to this fact, extensive beach-pools are preserved (photographs 3, 4 and 5), strangely enough the silt-sediment is very small here ( < 0,3 %). Transport of sand and formation of embryonal dunes are almost absent on these naturally wide beaches, of which the angle of inclination is less than 0,60 %. In Holland, Germany and Denmark, the wide and shelving sandbeaches are rarer, especially on the mainland. The angle of inclination varies between 1 % and 2% (cf. map 4A, 5A and 6A). As the difference in tide decreases in a northerly direction, there is also a decrease in frequency of subsequent active beachwalls; which on the other hand could be noticed along the French-Belgian coast. Typical for Denmark are the stone-beaches, in the vicinity of the moraine-cliffs, and the fossil sea-terraces, which can clearly be distinguished in the present beachcliffs. Going from the south (France) towards the north (Denmark), the quantity of shells and shell-waste gradually diminishes. North of Bergen (northern Holland), the shell-waste even becomes rare. The morphology of the dunes differs quite strongly from one beach-zone to the other. Southwest of Dunkirk, the dunevolume is very small. Only low duneridges follow in succession. In between, there are rather extensive, moist and thickly overgrown dunedepressions. Between Nieuwpoort and the Scheldt-estuary the actual dunelandscape is limited to a narrow, high duneridge. The dunezone between Dunkirk (Aa-estuary) and Nieuwpoort (mouth of the Yzer) reaches the width of 2200 m, and is the only zone of the northern French, Belgian and Dutch coast to have these systematical, wide parabolic dunes (cf. map 2A and 4A). Behind a carved foredune, which reaches the height of 12 m above floodmark, there are even two rings of parabolic dunes in succession and stretching parallel with the coastline between Bray-Dunes and Koksijde. The most southern paraboles (twelve or so) are 500 to 1300 m wide, and their axes indicate the same direction as the resulting wind-vector (N 75°). The southern arms of these parabolic dunes are in a direct line with each other, but the northern arms are mainly covered with a fresh rambling dune. This wandering dune is nothing but the southern arms of the smaller northern paraboli |
|
