COASTAL CHANGES MAPPING BY MEAN OF TOPOGRAPHIC MAPS, REMOTE SENSING AND GIS TECHNIQUES IN SAMBOROMBON BAY, BUENOS AIRES, ARGENTINA

A. Lamaro¹, S. Torrusio¹, J. Ulibarrena¹, H. Mugni², C. Bonetto²

1 - Universidad Catolica de La Plata, Instituto para Aplicaciones de la Teleobservacion N. Copernico, La Plata, Argentina

2 - Universida Nacional de La Plata, Instituto de Limnologia R. Ringuelet, La Plata, Argentina

storrusio@copernico.ucalp.edu.ar

The study area is the Samborombón Bay in the Atlantic Ocean (Argentine Sea portion), at the outlet of the Río de la Plata (west coast) in Buenos Aires Province, Argentina. The bay is 135 km long and stretches from Point Piedras (35°27′ S - 56° 45′W) to Point Rasa (36°22′ S - 56° 35′W).

The bay receives the Salado and Samborombón rivers, as well as other minor streams and canals.

The region is one of the most extensive, rich and important wetland of Argentina. The Samborombón bay was declared Ramsar Site in 1997, specially as acuatic birds habitat.

The coastal line in this environment experiments important variations by natural and/or antropic actions. These changes can be observed and measured along decades.

The main goal of this study was to develop a methodology to estimate and identify the changes in the coastal line in Samborombón bay by mean of the integration of: historic topographic maps (year 1936/37/38/39/41/68/71), satellite charts (years: 1994/95/96) and multitemporal satellite images of Spot (year 1998), Landsat 5 TM (year: 2005) and SAC-C (year 2005), the Argentinean satellite.

The steps to integrate the data were: 1) the data in analogical format was converted to digital format as the topographic maps and satellite charts; 2) the study area (coastal sector only,) was clipped from the original maps and images; 3) all the clipped material (maps and images) was georeferenced in the following Cartographic System: Transverse Mercator (Gauss Kruger), Ellipsoid: International 1909, Datum: Campo Inchauspe, Zone 6, by Nearest Neighbour algorithm as resampling method with ERDAS Imagine 9 software; 4) the topographic maps and satellite charts were mosaicked; 5) these three sources were integrated and analized in a GIS; 6) the coastal line was digitalized for the three temporal series of data: 1936-71, 1994-96 and 1998-2005 and the changes were estimated.

The results were different along the Samborombón bay: in the north (Point Piedras) the coast presented slight erosion, in the central portion (where the bay receive the main rivers) an important land increase was observed including new small islands, in the south (Point Rasa) an increase of the coastal line also was detected.

The applied methods and the obtained results were very useful to know the coastal changes and to update the cartographic information in this wetland, so important region from environmental point of view.