Evolution and dynamics of the dune bar of San Cayetano and Tres Arroyos counties, Buenos Aires.

Abstract

The coastal area of San Cayetano and Tres Arroyos counties was analyzed by mean of modern Landsat TM images (1999- 2000) and Corona satellite photographs of the year 1965. Data concerning climatic factors and beach morphology were added in order to understand aeolian dynamics and morphology of coastal dunes. The most important feature recognized was the reduction in volume of the dunes recognized as semi-fixed and fixed in 1965 mainly due to an increase in environmental moisture and a probable reduction of the sediment supply. A variation in wind direction from the north (1951-1960) towards the northwest (1951-1990) was evidenced, which modified the orientation of crests and propitiated the transition from barjanoids transverse dunes to parabolic dunes. Wind intensity in the SW sector during the analyzed period was the responsible for the maintenance of the dunes at the expense of a continuous degradation. The detailed analysis of some sectors by means of aerial photographs (year 1984) allowed the discrimination of morphological features in the evolution of parabolic and transverse dunes, which are of importance to discern the location, paleoclimatic events and migration of dunes. The antropic effect has been centered in the planting of arboreal species with the purpose of fixing dunes as well as tourist development (Claromecó, Orense and San Cayetano) The antropic effect do not alter the littoral drift. An increase in soil moisture (20 % increase in rainfall) probed the role of vegetation in controlling dune fields.