Hydrological and geomorphological processes in rivers: context and examples to interpret their response to episodes of high magnitude such as the Gloria storm

Abstract

Many rivers in Catalonia undertook a complete restructuring of its fluvial morphology under the effects of the storm Gloria. High magnitude flows caused profound changes in channel morphology, producing widespread incision and widening, flooding floodplains, and reconnecting abandoned channels. The episode contributed to a profound reactivation of river systems, and channels experienced a degree of metamorphism that had not been seen for decades. The study also shows the role of large dams in modifying flood hydrographs. The Gloria found rivers constrained by long-lasting human activity, with sediment balances in complete disequilibrium, and in clear water and sedimentary disconnection with the upstream river basin. Few hours of heavy rain and the subsequent hydrological response of the basins provided enough energy to exceed many of the physical thresholds to which they were subjected, and change the morphology of the affected river channels and valleys for a long time.

Keywords: magnitude and frequency, changes in soil cover, fluvial metamorphosis, flood hydrographs, morpho-sedimentary adjustments.