Correlações entre as dinâmicas geomorfológicas e pecuárias na margem esquerda do rio Madeira, município de Autazes (AM)

Abstract

This research analyses the Amazonian geomorphological dynamics in the left bank of the Madeira river in the municipality of Autazes (AM) until the confluence with the Amazon river. The economic structure of this municipality is centered on the primary sector, of which the bubaline livestock activity is responsible for the largest national milk production. The state of Amazonas is subject to an annual rainfall typical seasonality, which determines welldemarcated flood and drainage periods for the region's rivers. The riverine activities are thus controlled by the continuous modifications of the landscape resulting from pluvi-fluviometric seasonality.The energy present in the drainage system of rainwater and fluvial waters causes modifications in the relief resulting from the processes of margin collapse, erosion, transport and deposition of sediments. These processes stand out mainly in whitewater rivers, such as the Solimões / Amazonas / Madeira System. In this context, the present research has as general objective to understand the implications of local livestock activities based on the relationship between natural and anthropic dynamics in the flood plain of the left bank of the Madeira river. To achieve this objective, the following specific objectives were defined: (i) to qualitatively analyze the dynamics of the Madeira river system and the riverine relationship with the seasonal change of the landscape; (ii) to evaluate how river erosion processes and mass gravitational movements interfere with riverine livestock practices; (iii) to perform geomorphological mapping from remotely sensing data and field work, and (iv) to define strategies for the use of flood plains based on the New Brazilian Forest Code. The applied methodology consists in the bibliographical survey, the collection of cartographic data, the execution of field work during the flood and ebb period, interviews on the socioeconomic and landscape aspects resulting from the seasonal change of the landscape and fallen lands and the digital processing and the interpretation of visual and automatic orbital images. The results obtained allow us to verify the intrinsic relationship maintained between riverine populations and the fluvial dynamics, such as the transfer of the flood plain production systems to firm ground, the oscillation in the commercialization of product prices, difficulties in locomotion, mass gravitational movements by rotational sliding and block falls, and the seasonal change of the landscape due to the flood and ebb periods provided by the fluvial dynamics of the Madeira river. Based on these results, it can be verified that the relationship between fluvial geomorphological dynamics and the development of livestock activity is established in a different way according to the purchasing power of the four social classes identified in the study area, as follow: the owners of firm ground (class A); those with pieces of firm ground and lowland (class B); Those that only have plots in the lowland areas (class C) and those without access to the large productive system, the livestock, grouped in class D.The above mentioned classes are established in relief units of average slope (0 to 20%), not exceeding values of 50m of altitude, based on the mapped formations of homogeneous tabular plateau, terraces and fluvial plain, with presence of a dense drainage network of paranás, holes, lowland lakes and adapted to the tectonics, and igarapés of both sub-dendritic and dendritic patterns, and the formation of islands, sediment bars, deltas, sandy cords and river dikes. The awereness of this geomorphological context and of the socioeconomic relationship in the study area evidences the need for specific measures in the environmental context. The Crop- Livestock-Forest Integration System (ILPF) and the Agroforestry System (SAF) are indicated for the maintenance and development of these environments.