Landsat ETM + imagery and SRTM data application to hydrological analysis: a case study in the As‑Saquia El Hamra watershed (Saharan Plateau, Morocco)

The As Saquia El Hamra watershed is located in the southern part of Morocco, covers an area of 81 000 km2. Toward the west, the Oued As Saquia El Hamra flows into the Atlantic Ocean. During flood periods (1987, 2003, and 2016), the study area experienced severe flooding, causing in significant material and human damage, especially in Laâyoune city. The physi ographic and geometric characteristics of this watershed basin significantly contribute to the amplification of this natural disaster. Many tools were used to solve the mentioned problem, including spatial Remote Sensing (RS) and Geographic Information System (GIS) techniques. Spatial analysis of the Oued As Saquia El Hamra has provided comprehensive geologi cal, geomorphological, hydrological, and climatic information about the region. This present study aims to investigate the relationship between the drainage network, geomorphology, and geology of the watershed. It seeks to determine the origin, evolution, and extent of this network in relation to various lithological facies and paleo-climatic conditions. As a results, the hydrological Analysis indicate the presence of a main river that spans 400 km. Its exorheic drainage features a dendritic net work, intermittent tributaries, wide riverbeds, and branched, anastomosing or meandering patterns in the riverbed. Regarding the lithology data, it influences the configuration of the drainage network and divides the watershed into two sub-watershed. On the other hand, sea level fluctuations and climate change play a crucial role in reconstructing of the geological history for hydrographic networks and the drainage systems that have developed since the post-Miocene. Additionally, mechanisms such as such as tectonic effects and anthropogenic factors influence the formation of these drainage networks. Thus, digital data and modeling can be used in various areas of geo-prevention, including natural hazard mapping and land use planning.