Statistical approach of factors controlling drainage network patterns in arid areas. Application to the Eastern Anti Atlas (Morocco)

International audience12 13 Abstract: 14 Several studies have revealed that the complexity in the distribution of drainage network patterns is not 15 random and controlled by major parameters, variable in space but also throughout geological time. Drainage 16 networks in the Eastern Anti-Atlas of Morocco consist of complex spatial arrangements with various types of 17 patterns, such as trellis, angular, dendritic and parallel. The objective was to distinguish, quantify and rank 18 the relationship that may exist between the different drainage networks patterns, geology and 19 geomorphology. A total of 230 basins were extracted from the ASTER-GDEM Elevation Data (USGS), which 20 were assigned 16 parameters reflecting their topography, morphometry, slope and geology. The statistical 21 treatment of the dataset (16 variables x 230 observations) was carried out through principal component 22 analysis (PCA), linear discriminant analysis (LDA) and agglomerative hierarchical clustering (AHC), in order to 23 investigate the complexity of drainage network patterns and their distribution. The PCA showed that the 24 topographical, slope and geological parameters, i.e. primarily the parameter associated with structural 25 control, best explains the variation in the type of the drainage pattern. The LDA made it possible to distinguish 26 between the four types of drainage patterns with a success rate of 90%, using 3 discriminant functions that 27 were better correlated with geological and slope parameters. LDA and AHC statistical treatments show 28 confusion between the parallel, trellis and angular patterns, on the one hand, due to similar factors 29 responsible for their formation, and on the other because of transitions phenomenon from one drainage 30 pattern to another over time or space. Such possible drainage network shifting may be explained by the 31 geological events that have occurred in the Eastern Anti Atlas from Lower Mesozoic to the Quaternary. 32 3