Soil erosion and hydroclimatic hazards in major African port cities: the case study of Tangier

Abstract

Land degradation and soil erosion are becoming increasingly problematic in Africa's rapidly developing urban areas, particularly in Major Port Cities. Uncontrolled expansion and human pressures are hindering planning, adaptation, and conservation efforts. To understand the extent of these issues, this study combined morphometric analysis, soil loss calculation, field monitoring, and remote sensing and GIS tools to assess soil erosion in the Metropolis of Tangier (Morocco) located at the confluence of the Mediterranean Sea and the Atlantic Ocean at the Strait of Gibraltar. The study relied on data from 13 rain gauge stations, official reports, and remote sensing acquisitions, as well as field observations. Results showed an average soil erosion rate of 24.2 t/ha/year, equivalent to an annual soil loss of 588,051 t/year. This high rate was largely due to areas with a high erosion risk (99.8%), covering only 8.3% of the territory, which were characterized by recently burned topsoil, fallow land, and steep slopes. These areas included both uncontrolled neighbourhoods and areas for planned urban and industrial expansion, posing a threat to the landscape's sustainability and socio-economic prospects. The morphometric analysis revealed its high vulnerability to erosion and degradation, with the highest soil loss rates observed in the eastern and western regions. The study also found that flash floods caused by hydroclimatic hazards can lead to significant damage to infrastructure and equipment, particularly in western sub-basins and mountainous regions. In conclusion, the use of remote sensing and GIS technologies provided valuable insights into the physical characteristics and vulnerability of the Tangier Metropolis to land degradation and soil erosion. These findings emphasize the need for effective land management practices and conservation measures to mitigate the impacts of land degradation and soil erosion in the face of climate change. This information is crucial for decision-makers and stakeholders to develop strategies to address these pressing issues.