Fluvial connectivity in Araripe sedimentary plateau, Brazilian semi-arid

This study aimed to characterize the different settings of fluvial connectivity in a semi-arid watershed, in the northeastern portion of the Araripe sedimentary plateau, to the south of the state of Ceara. The proposed models emphasize morphologies and adjustments in a historical scale, using inherited surface covers, climatic dynamics, lithology and land use transformations as controls, coupled with landscape intrinsic hydrological processes. Fluvial impediments were mapped, followed by their classification, based on the distribution between landscape compartments and connection processes. The first-order tributaries of the Salamanca River rise from the entrenchment of sedimentary deposits at the base of the escarpment or downstream of talus deposits, resulting in different hollow filling configurations and different paleoconectivity evolution scenarios. Gorge valley stretches, downstream, lead to the confinement of the flow, accelerating connectivity, with a predominance of vertical erosion. The most expressive disconnection element of anthropogenic origin in the Salamanca River watershed is an artificial canal, part of the project for transposing the waters of the Sao Francisco River to smaller watersheds in the state of Ceara. The raceway borders the sedimentary plateau, modifying or obstructing the flow of lower order drainages and obliterating the laminar flow hillslopes to their base levels. In the Peripheral Depression (Vale do Cariri), fluvial morphologies alternate sequences of arroyos (channeled stretches) and floodouts (non-channeled stretches), controlled by the "cut and fill" dynamics prevalent in alluvial plains. Among the environmental controls operating in the analyzed scenarios some stand out, such as the lithology of the sedimentary basin, which reflects itself in the high availability of sediments and the spatial distribution of continuous and discontinuous floodplains; the "cut and fill" dynamics associated with the semiarid hydrological regime; and changes in land use, with the replacement of traditional agricultural practices, expansion of urban areas and construction of water works to watershed transposition.