Stream channel development in the southern parts of the High Atlas Mountains, Morocco

Abstract

The aim of this study is to review current knowledge on channels development in mountain basins in arid zones. The research was intended to describe the main triggering factors responsible for the development of ephemeral river channels in such areas. A detailed study was made of the Upper Dades basin located on the southern slopes of the High Atlas Mountains (Morocco). In this paper we analyse the morphometry of channels of different orders in three small basins chosen for a thorough study in order to present the details of channel characteristics.The results show that the development of stream channels of the same order may vary greatly. This is mainly due to variation between the basins in lithology, vegetation cover, precipitation amounts and hillslope sediment supply. We prove however that the key agents of stream channel development are the energy of water and associated mass gravity movements in the period when water is absent. The morphological component provides strong evidence for this conclusion. The results show that runoff energy generally compensates for the low amount of water in 2nd and 3rd order channels where erosion is dominant. The 4th order channels are therefore better adapted to evacuate significant discharges (weak slope, large channel) which therefore decreases the erosive capacity of their stream flows. In this paper we also discuss whether the impact of the limited hillslope vegetation and the supply of coarse-grained sediment in the channels are important in the development of channels in mountain basins in arid regions. We conclude that intense rainfall-runoff events that lead to short-lived but high-energy flash floods have a more significant impact in contemporary channel development. Channels, especially those of 3rd and higher order, tend to be very unstable during large floods. We show that channels located in small basins in mountains in arid zones are in a state of almost permanent non-equilibrium.

Which DEM is best for analyzing fluvial landscape development in mountainous terrains?

“…Superimposed onto the high relief caused by this tectonic uplift are sedimentation and erosion patterns, such as river terrace sequences, linked to Quaternary climatic fluctuations and the underlying strength of the bedrock lithology (Stokes et al, 2017). At the present time the area is characterised by a semiarid climate with altitudinal zonation, where annual precipitation varies from ~150 mm/a in the basin to 200 mm/a in the headwaters (Schulz et al, 2008;Dłużewski et al, 2013).…”

Bedrock structural control on catchment-scale connectivity and alluvial fan processes, High Atlas Mountains, Morocco

“…Precipitation in the upper elevation of the catchment ranges from 200mm pa upstream (M'smerir, Fig. 1c) to 150mm pa downstream (Boulmalne du Dadès, Fig 1c) (Schulz et al 2008;Dłużewski et al 2013). The tributary fans that form the focus of this study are ephemeral tributary catchments developed within the lower elevation, more arid zones.…”

Simultaneous growth releases and reductions among Populus alba as an indicator for floods in dry mountains (Morocco)

“…The sub-catchment area of alluvial fan at DAD1 site is 22.73 km 2 with the gradient of 0.08. The sub-catchment of the fan at DAD2 site is much smaller: 2.95 km 2 and steeper with 0.28 gradient (Dłużewski et al, 2013;Rojan, 2019).…”