Flow intermittency and river styles in tropical non-perennial rivers

This study investigates the parameterization of flow intermittency and river styles in two hydrographic basins in the semi-arid region of Paraíba: the Paraíba and Piranhas rivers. The research adopts an integrated approach combining the Base Flow Index (BFI) and the analysis of river styles (River Styles—RS) to characterize the basins' hydro-geomorphological dynamics and spatial variability.

The results indicated that both rivers exhibit flow perenniality below 5%, with the Paraíba River showing higher intermittency than the Piranhas River. The analysis revealed different patterns of intermittency, classified into subclasses based on the frequency and duration of zero-flow events. Additionally, river styles were categorized as confined, partially confined, and unconfined, with significant variations in geological controls and morphological characteristics. Among the confined styles, rocky beds associated with high-flow energy and the absence of floodplains were highlighted. Conversely, unconfined styles exhibited extensive depositional areas and greater connectivity.

The analysis of river styles employed tools such as remote sensing and fieldwork to map geomorphic units and determine bed material texture. Confined reaches showed high sediment transport competence, whereas partially confined and unconfined reaches demonstrated greater susceptibility to geomorphic adjustments in response to environmental changes and climatic variability. The identified patterns underscore the importance of flow intermittency as a determining factor in the morphodynamics of semi-arid fluvial systems.

The data also revealed that the São Francisco River's transposition directly influences the studied basins' hydrological dynamics. This artificial water input alters the natural flow regimes and contributes to geomorphic processes and river connectivity changes.

In conclusion, the study contributes to the understanding of intermittent rivers in semi-arid regions, emphasizing the relevance of integrating hydrological and geomorphological aspects into the sustainable management of water resources. The applied methodology provides a robust scientific foundation for future research on the interaction between climate, geomorphology, and hydrology while highlighting gaps in the literature related to fluvial adjustment rates in dry environments.

Keywords: intermittent rivers, semi-arid, river styles, hydro-geomorphology, water resource management.