The role of historical sources in the functional representation of a river in the New World. The case of the argentinan Paraná
Résumé
How can we understand and construct a New World with European benchmarks that do not necessarily apply in this environment? In order to discover and appropriate a territory, its nature must be touched. Therefore, the body of the Paranà river has changed, with the scars of territorial colonisation remaining today. How do different cartographies represent the fluvial dynamics of a New World river? How do the maps lead to the identification of this change? By adopting a global framework across the Argentinian Paraná, we seek to identify changes in river dynamics. The geohistorical approach using old maps gives a new representation of the Paraná. Our archive research allowed us to collect 43 maps depicting a period covering the fifteenth to the twentieth century. The scales of analysis also vary: the maps show the Paraná from its regional integration (1/100,000) up to a continental scale (1/18,500,000). The validation of the cartography is performed by comparing the representations with descriptions of the river found in texts dating from the same period. The methodology used is a map-to-map comparison, following the theory of river systems (Schumm, 1977). Therefore, sandbanks, islands and river planforms are considered to be markers of the river dynamics. The maps thus provide an answer: it is possible to trace the causes from the results. The causes are themselves related to the spatial and climatic phenomena. Early maps show a braided planform in the upper reach of the Paraná and a Paraguay channel free of deposits. The current dynamics indicate an inversion in sedimentary transportation and deposit. The deforestation mechanisms in the Misiones territory and their abandonment could lead to a shift in the sediment load. This hypothesis will be demonstrated through analysis of the maps, its validation by texts and the results of a field study.