Caracterizacao multitemporal de barras e ilhas fluviais no baixo curso Do Rio Jaguaribe, Ceara-Brasil

Abstract

This study provides a characterization, based in a multiple time series, of the bars and river islands along Jaguaribe river's lower course, especially in the segment downstream of Castanhão reservoir's dam, both in years of drought and of heavy rain conditions. The methodology deployed in the study consisted of establishing both dry and rainy standard years and using remote sensing tools, such as aerial photographs, satellite images and geoprocessing software, to map the different typologies of bars and river islands. According to the results obtained, despite the distinctive elements found in the morphological data on the quantity and area of the different typologies of bars and river islands, generally, the formation of these features reflects flow variations occurring in Jaguaribe river's lower course, as evidenced by the data obtained via the Pearson correlation coefficient and the coefficient of determination. Therefore, in dry years, these features were reduced because the flows were not significant enough to effectively transport sediments. On the other hand, in rainy years, there was an increase in river bars mainly due to the cyclical action of erosion and sedimentation processes, which distributed and redistributed sediments along the channel. Furthermore, the bars position in the channel (lateral or central) was found to affect the correlation's scale even more than its form/geometry (headland), the formation of which is directly linked to other geomorphological factors.