Semi‐arid river dynamics from the internal geometry of river deposits

This article contributes to studies of river geomorphology through the application of Ground Penetrating Radar (GPR) to reconstruct the morphostratigraphy of river aggradation forms in drylands based on a case study in the semi‐arid region of the Brazilian Northeast. Four stratigraphic sections were created based on the interpretation of radargrams generated during geophysical prospecting, using a GPR with a 200 MHz antenna and a topographic survey in transects across the Riacho Grande Creek valley bottom. Radargram profiles were crucial for understanding fluvial dynamics from floodplain deposits, with the predominance of flat to slightly channelled reflectors being observed, representing the dynamics of cutting and filling of floodplains. However, the granulometry of the river sediments influenced the visualisation of the deposits’ depth and the detailing of the radar facies. The predominantly sandy deposits allowed a detailed recognition of the stratigraphy and reconstruction of the associated morphogenesis. The study was enhanced by a comprehensive qualitative analysis of local climatological series spanning the past three decades. The objective was to investigate the relationship between extreme precipitation events and river dynamics, particularly focusing on the morphological responses such as the development of depositional features along river channels. The radargram responses obtained from the four detailed profiles successfully delineated the dominant depositional styles within the alluvial plains. The application of GPR should be further promoted, particularly in arid and semi‐arid regions, where there is a pressing need to assess the water storage potential of fluvial deposits.