Bedrock rivers are increasingly becoming of interest due to their significance in controlling upstream
entrenchment by fixing the base level. Longitudinal profiles are dependant not only of discharge but also
on incision capability due to bedload transport thresholds determined by gradient availability. The lower
Guadiana River incises into the large Extremadura-Alentexo planation surface, developing large canyon
carved on extended flat rocky benches with internal channels. Their development cannot be understood
as that of simple hydrodynamic features produced and backwards erosion by lithologic control. In order
to determine drainage network evolution in relation to regional surfaces and tectonics, longitudinal profiles
river profiles from the Guadiana River and its tributaries have been reconstructed and their concavity
index and mathematical fitting curves analysed. Different reaches might be interpreted on a morphostructural
framework, with convex river profiles adjusting to active base level lowering as compared to the more
stable and better evolved upstream rivers. To explain the convexity towards the south, one must consider
the subsidence of the Guadalquivir flexure, which coincides roughly with the Guadiana mouth