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Rivers are one of the geomorphological agents that most leave their mark on natural landscapes, presenting a dynamic of production, transport and deposition of sediments. The cross-section, the layout and the slope of the channel are characteristics of the fluvial channel that change in a very short time, and these changes may be natural or anthropic. The present study was carried out on the Jaguaribe River, one of the main intermittent river courses in Ceará state, Brazil, whose flow is perpetuated by the Castanhão dam. The objective of this work is to compare the magnitude of the flows with the morphological changes in the cross section of the fluviometric station of Quixeré (period 2006-2019). For that, the return time and the probability of occurrence of the maximum annual flows were determined by Weibull formulas. The study of morphological variation in the cross-section was based on the analysis of topographic profiles using the statistical parameters of Olson-Rutz and Marlow (1992). The results showed that the cross-sectional area, in a period characterized by high flows (2008-2009) and low flows (2016-2019), varied around an average value (1,484 m2), characterizing a condition of equilibrium. Statistical parameters showed that the cross-sectional area, modified by the sum of erosion and deposition during high or low flows, varied in very similar percentages. On the other hand, the magnitude of the predominant erosive or depositional process was greater in periods with high flows than periods with low flows. [ABSTRACT FROM AUTHOR]

Erosion of riverbanks is a natural process that can be intensified by human activities, producing catastrophic effects on the river environment. The understanding of this process is fundamental, for the studies related to fluvial geomorphology, beyond providing environmental imbalances, can cause problems of social and economic order. The present study had the objective of analyzing the dynamics of the riverbank erosion processes in the Jaguaribe river, in its low course, precisely in the municipal of Quixeré. The Jaguaribe River is one of the main springs of the state of Ceará, being a semiarid river and having its flows controlled by dams. For the monitoring of the margins, nine sections were selected along a 10 km section of the river, which were grouped into three types, Conserved Area (CA), Conserved Partially Area (CPA) and Degraded Area (AD). In order to quantify the erosive rates, the methodology of the erosion pins was used. The results obtained show that the degraded areas presented values of retreat 13,5 cm year-1 and eroded volume of 7,77 m3, with the highest values observed, and those that were conserved had retreat values of 3,05 cm year- 1 and volume of 1,39 m3 year-1, accompanied by partially conserved areas that obtained values of retreat of 4,85 cm year-1 and volume of 1,52 m3 year-1. For the period evaluated (June / 2014 to May / 2015), rainfall was the main condition responsible for marginal erosion, even though rainfall was below the historical average. [ABSTRACT FROM AUTHOR]