Hydromorphological analysis of the middle Sebou river system (Eastern Saïss basin, Morocco): Functioning, morphogenesis, and antecedent controls

Abstract

The hydromorphological characteristics of the Middle Sebou Valley were examined across various scales within a nested fluvial system, including catchment, landscape unit, valley segment, reach, and geomorphic unit. This study aims to explore hydromorphological functioning, morphogenesis of sedimentary forms, and antecedent controls on contemporary hydromorphological processes. The valley spans two distinct landscapes: the tabular plateaus of the Middle Atlas and the hills of the Saïss foreland basin. The valley is divided into three homogeneous reaches based on the landscape unit traversed and the valley setting, including the degree of confinement, the absence or presence of the floodplain, and the channel planform. In the Plateaus landscape unit, the upstream reach R1 is confined to deep gorges and displays a sinuous pattern. In contrast, the middle reach R2 in the rounded hills landscape unit is partially confined, showing a sinuous to slightly sinuous pattern with entrenched meanders and a tendency to braid. Finally, the downstream reach R3 is laterally unconfined and generally meandering, with free meanders. Along these reaches, floodplain pockets are respectively absent, discontinuous, and continuous. Each type of reach is characterized by an assemblage of instream and floodplain units genetically linked by a process-form association and by a different natural capacity for adjustment. The geomorphic river diversity and its behavior along the Middle Sebou catchment are shaped by the imprint of geological, climatic, and anthropic memory, which continues to influence contemporary processes.