Impact of Catchments Morphology and Lithology on Stream Channels System in High Mountains of Arid Zone (Example of High Atlas, Morocco)
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Several factors control the morphodynamics of stream channels in high mountains of arid zone. The aim of the paper was to analyze the relation between stream channels system, catchment morphology and lithology based on examples of three small catchments of ephemeral streams that are tributaries of the Dades River (High Atlas, Morocco). The research included analysis of the topographic and the geological maps, LANDSAT, Google Earth images and the geological and geomorphological field survey. The results showed that the drainage density is strongly controlled by lithology. In the catchment built of conglomerates, the density of stream channels is almost one and a half time greater than in catchments built of limestones and almost twice as large if we take into account only initial channels. Tectonics impacts the stream density to a lesser extent. Two catchments built of limestones which are strongly fissured due to joint system and some faults are characterized by much lower drainage density than the catchment built of conglomerates where signs of discontinuous deformation are sparse. The stream channels of high-order formed in conglomerates are wide and low-gradient, whereas the initial and the first-order channels are narrow, deep, and closely spaced. In catchments built of limestone, the relation is reverse.
KeywordsRiver channels system Catchments morphology Catchments lithology High Atlas Arid zone
This work was supported by the Polish National Science Centre, project No. 2011/01/B/ST10/07295.
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