Abhatoo - Centre Nationale de Documentation

Within the context of climate change and increasing demographic pressures, problems of water resources variability have become particularly crucial. The management of arid watersheds, which are highly exposed to droughts and floods, needs to be supported by a thorough understanding of their susceptibility to these hazards. The watershed of Tensift in Morocco includes a high mountainous area and a large alluvial plain. In the mountainous part, the bedrock has a low permeability and steep slopes, while the main valleys are narrow and deep. The important rainfall events, which are usually short but intense, are favoured by high elevation and good exposure to oceanic disturbances. Furthermore, predictions of climate change consequences on several socio-economical fields in Morocco are very alarming. For example, climate trends and future climate projections at Marrakech show a clear trend towards higher temperatures and lower rainfall. Consequently, surface water resources are directly affected and the flows of Tensift river have fallen significantly. For the extreme events, the conjunction of physical and climatological factors in the mountainous basins, is at the origin of violent floods, which are characterized by the highest velocities and peak flows. The frequency analysis of floods shows that these extreme events are repetitive with a variable intensity. The rising time of floods is very short, and human and material damages can often be substantial. plain's floods are slower, but their water volumes are very important and can submerge wide areas around the rivers as the case of the flooding of November 30, 2014.