Influência da sazonalidade eco-hidrológicas e biogeomorfológica em rios não perenes

Abstract

This thesis analyzed the influence of eco-hydrological and biogeomorphological seasonality on the morphology of non-perennial rivers in the Riacho do Tigre basin, located in the semi-arid region of Paraíba, Brazil. The main objective was to examine how eco-hydrological and biogeomorphological seasonal dynamics control the morphology of non-perennial rivers, particularly by understanding how seasonal hydrological variations influence vegetation distribution and resilience, as well as channel morphological evolution.The methodology integrated multiscale analyses: at the drainage network scale, using Sentinel-2 NDVI time series (2016–2023) and rainfall data; at the reach scale, through UAV-based monitoring for the production of orthomosaics, digital terrain models (DTMs), and calculation of the VIgreen index; and at the quadrat scale, using permanent plots to monitor ecological succession across different geomorphic units (channel bed, bars, and margins).The results demonstrated a strong positive correlation between NDVI and accumulated precipitation (60–90 days), highlighting the rapid response of vegetation to rainfall pulses. Monitoring with VIgreen revealed marked seasonal dynamics, with increased vegetation biomass during the rainy season and reduction during dry periods. Quadrat monitoring showed that geomorphic units such as pools and margins sustain higher vegetation diversity and stability, whereas bars and active channels exhibit greater species turnover. Morphological analysis identified the instability dynamics of unvegetated sediment bars, in contrast to the stability of vegetated bars, which were only significantly reshaped by extreme hydrological events.It is concluded that the interaction among hydrology, geomorphology, and vegetation constitutes a non-linear system, sensitive to specific hydrological thresholds, with seasonality acting as a key driver of morphodynamics and ecological organization in non-perennial channels. These findings highlight the importance of incorporating eco-hydrological and biogeomorphological approaches in the understanding and management of fluvial systems in semi-arid regions.