Modelagem da inundação de florestas de várzea do estuário amazônico

Abstract

The Amazon Basin is composed of the most extensive hydrographic basin in the world, producing approximately 20% of global freshwater discharge. Both biodiversity and human livelihoods are affected by water levels in the basin, which vary throughout the year and along the spatial gradient of the river system. Water levels in the Amazon Estuary are affected not only by precipitation levels, but also by semi-diurnal tides. Analysing data from three tidal gauges installed along the estuary at increasing distance from the coast shows that the tidal variations in tributaries of the Amazon estuary are strongly related to predicted tides at the coast, meaning that these predictions could be extrapolated throughout the estuary. Seasonal and tidal effects are apparent in all three tributaries and the tidal ranges are, on average, between 2.1 and 2.4m which identifies the region as one of “meso-tides”. The data show that tidal ranges decrease with increasing distance from the coast, and that the high and low tide peaks occur later further inland. These results have important implications for management of tidal várzea, and for planning of fluvial transport of all types in the Amazon estuary. In order to better understand how the inundations affect human and plant communities in specific regions it is necessary to determine the duration of the period of inundation in this region throughout the year. The second part of this study therefore had the objective of developing a model of inundation, using the spatial modelling platform Dinâmica EGO, to simulate the time for which each area would be flooded, according to its elevation. The inputs to the model include microelevation, information regarding drainage canals, and variation in tidal levels. The model results conform with the findings of chapter one in relation to tidal patterns along the estuary. The results show that in the month of June, chosen to represent the period of highest precipitation, the area flooded is larger and the duration of flooding is longer, in all lunar phases, in comparison with the month of November. Indeed, in November the flooded area was substantially less than in June, and the duration of flooding was also less. Therefore, it was possible to develop a model that represents the realities of várzea forests using the software Dinâmica Ego