Morphological changes using cross-sectional studies in a semi-arid highly dammed river:a case study on the Jaguaribe river in the municipality of Quixeré - Ceará

Abstract

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.