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Present Day Dune Processes and Dune Morphology on the Łeba Barrier, Polish Coast of the Baltic

Ryszard K. Borówka
Geografiska Annaler. Series A, Physical Geography
Vol. 62, No. 1/2 (1980), pp. 75-82
Published by: Wiley on behalf of the Swedish Society for Anthropology and Geography
DOI: 10.2307/520454
Stable URL: http://www.jstor.org/stable/520454
Page Count: 8
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Present Day Dune Processes and Dune Morphology on the Łeba Barrier, Polish Coast of the Baltic
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Abstract

Relations and interdependence between factors determining the processes of eolian transportation and deposition and results of these processes were studied in the area of the Łeba barrier on the Polish Baltic coast where modern eolian processes are intensive. From quantitative studies of transport intensity it was found that: (1) Transport intensity is approximately proportional to the 4.68 power of wind velocity measured 1 m above the ground, and calculated indices of wind effectiveness showed that storm winds even of short duration are the most significant for creation of the eolian relief. (2) Transport intensity is inversely proportional to air temperature which explains, among other things, the particularly high efficiency of eolian processes in winter and fall periods. (3) Ground moisture does not hinder eolian transportation, especially not at high wind velocities. (4) Increase in transport intensity is inversely proportional to a height element of the surface roughness. Even microforms, e.g. ripple marks, cause a distinct decrease in transportation. Distinct dependencies were found between the character of the surface face and the sand stream structure since it turned out that: (1) The thickness of the sand stream is not only a function of wind velocity, but also depends on surface moisture and roughness. Over a moist and smooth surface the thickness of the sand stream is considerably larger than over a dry rippled surface. (2) The sand stream is denser over the latter rippled bed. The transport studies and observations of microforms and mesoforms made it possible to distinguish a group of factors influencing morphology, structure and texture of depositional forms: (1) In the case of a dune field it is not wind velocity but surface roughness and ground moisture that have a decisive influence on dune morphology. In humid periods, mainly deflation relief is formed, while in dry ones, a whole set of depositional micro and meso forms develops. (2) The size of the smallest depositional forms (ripple marks) in proportional to the average grain size and inversely proportional to the degree of sorting in these forms. (3) Differentiation in graining in the distal slope of a dune depends more on the character of the proximal slope and sand moisture than on wind velocity. (4) Depositional intensity and humidity of the deposited sand have a direct in influence on gravitational motion in the distal slope, and an indirect influence on graining and development of disturbance structures.

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