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What Are the Risks of an Increase in Mean Sea Level?

Argentina Coast Vulnerability Assessment Built Around GIS

The United Nations Development Program and the United States Global Environmental Facility recently pursued a study of climatic change in Argentina. One of the subprojects, EVANM (by its spelling in Spanish), was to produce a vulnerability assessment of the coasts of Argentina under the risk of an increase in mean sea level by 2100. EVANM was based on preexistent information and data gathered by a team of more than 20 researchers pertaining to eight academic, national, and provincial organizations.

Given the extent of the Argentine coast (more than 5,700 km) and the time constraints (only 18 months), it was decided to work along a stretch of the coast that fulfilled the following requirements:

  • Variable coastal geomorphology representative of all types of coasts in the country
  • Balance between densely populated areas (coastal towns, harbors, piers, jetties, etc.) and uninhabited zones
  • Accessibility in order to carry on fieldwork
  • Availability of preexistent information and data

The coast between Punta Piedras and Punta LaberintoAll these requirements were fulfilled by a sector of the coast of Buenos Aires Province that extends between Punta Piedras and Punta Laberinto. This sector presents wetlands, beaches, sedimentary cliffs, old rock exposures, coastal dunes, and estuaries typical of the Argentine coastline. Although many major resort cities and harbors are located in this part of the coast, extensive uninhabited areas also exist.

On the other hand, taking into account the economic aspects of the area, this sector includes three of the most important harbors of the country, and tourism--which constitutes a major activity in the region--could be affected substantially by changes in the mean sea level. Also, the lands behind the coastal areas--internationally known as the Pampas--are probably the richest in the country for agriculture and cattle ranching.

Once the study area was defined, to assure a correspondence with similar studies carried out in other countries of the world, EVANM adopted a working methodology based on the Common Methodology prepared in 1991 by the Intergovernmental Panel for the Climatic Change and on the Guide for Vulnerability Studies and Adaptation prepared by the U.S. Country Studies Program (1994). This included filming the coast from 100-meter and 300-meter altitudes and field ground control. The methodology also included digitizing available charts, satellite image analysis, data gathering, and database management.

From the beginning of the project it was clear that the most complex task would be the summary of all the information of the socioeconomic aspects and of the physical environment of the region, the interrelation of the different thematic cartographic coverages generated at various scales, and the exchange among the multiple databases.

For this reason, the structure of the project was built around a GIS. The chosen system was ArcInfo, with viewing, handling of the cartographic coverages, and space consultations carried out using ArcView GIS.

Vulnerability Analysis

Overlapping and analysis of the coverages were useful in defining the coastal vulnerability with regard to the level of erosion and accumulation.Overlapping and analysis of the coverages were useful in defining the coastal vulnerability with regard to the level of erosion and accumulation. Three basic criteria were defined: accumulation, weak erosion, and strong erosion. Accumulation areas correspond to places in which there exists a natural net deposition of sediments and, in consequence, a low vulnerability index are indicated.

Areas with weak erosion are associated with uninhabited sectors, while the coastal dunes behave as sediment storage.

Overlapping and analysis of the coverages were useful in defining the coastal vulnerability with regard to the level of erosion and accumulation.Finally, areas with strong erosion and high vulnerability correspond with reaches of shoreline that are distinguished by the absence of coastal dunes, active cliffs, or high modification by humans.

The study showed that two sectors were at high risk should there be a sea level rise between one and two meters. One of them, Bahía Blanca estuary, incorporates numerous islands, islets, channels and tidal flats, and the Colorado River delta and is part of the Provincial Natural Reserve. The main loss here would be linked with flora and fauna populations typical in the region. There are also two beach resorts that may suffer some economic setback.

By far the largest impact would begin at Samborombón Bay since it would suffer important economic losses. About 2,400 kilometers of wetlands and grasslands would be flooded. Considering an estimated cost per hectare of $500, property valued at about $120 million would be covered by water. This area also includes a natural park run by the Argentine chapter of the World Wildlife Fund. Here the foundation is studying an almost extinct species of deer known as deer of the Pampas.

Coastal types and vulnerability to erosive processes are shown.As bad as the Samborombón Bay impact itself would be, a much larger impact would happen inland of the bay along the very flat Salado River basin, which covers about 50 percent of Buenos Aires Province and parts of La Pampa, Santa Fe, and Córdoba provinces. This area is the nucleus of the agricultural production of the country. Even a minimum sea level rise will strongly affect the water discharge of the system both by reducing the runoff and preserving large volumes of water along the basin and flooding the fields. The losses would be incalculable. A preliminary assessment of the possible losses is very difficult since the values are related to seasonal variability in the rainfall and the period in which the agricultural activities occur.

Proposed Strategies

It is evident that in the area of Samborombón Bay, a major strategic management plan for the Salado River basin is required. In the meantime, EVANM proposed strategies for the remainder of the coast that included controlling the extraction of beach sand, managing and reducing urban development near beaches and cliffs, limiting the opening of streets perpendicular to the coast and across the dunes, renourishing beaches, and suspending (or limiting to special cases) jetty and wave breaker construction.

For more information, contact Dr. Gerardo M.E. Perillo, Instituto Argentino de Oceanografía (IADO), P.O. Box 107, Km 7 "La Carrindanga," CP 8000, Bahía Blanca, Argentina (E-mail: perillo@criba.edu.ar). All three authors are affiliated with the Instituto Argentino de Oceanografía. Gerardo M.E. Perillo is also with the Department of Geology, Universidad Nacional del Sur, and Guillermo R. Angeles and M. Cintia Piccolo are also with the Department of Geography, Universidad Nacional del Sur.

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