Conditioning Factors of “Terras Caídas” in Lower Solimões River - Brazil

Abstract

The term “Terras Caídas” is used in Amazon to refer to processes of fluvial erosion and mass movements of large and moderate scale. It is a dynamic and complex multi-causal process that involves hydrodynamic, hydrostatic, climatic, neotectonic, lithological and anthropic factors, occurring together or separately. The objective of this work is to understand the conditioning factors of the phenomenon "Terras Caídas" in lower Solimões River - Brazil. For this purpose, the study area was monitored for 2 years (2017-2018) and data from satellite images; water discharge; flow velocity; suspended sediments; water level; precipitation; wind direction; seismic activity were obtained. The hydrodynamic factors and the rain influence the “Terras Caídas” more intensely during the river flood, the processes influenced by the wind direction occur throughout the hydrological year, but with greater intensity during storms. Hydrostatic pressure occurs more frequently in ebb causing landslides. The lithology influences the stability of the banks due to unconsolidated sediments, providing erosion and mass movements. It is observed that neotectonics was not important in increasing the intensity of the "Terras Caídas" in the study area in recent years. Human activity influences destroying riparian forests and the basal erosion caused by waves formed by boats the region.