Incidence des grands travaux d’infrastructures sur les milieux naturels : cas du tronçon pk0-pk20 de l’autoroute Yaoundé-Douala

Abstract

The aim of this research is to analyze the implications of construction of the PK0-PK20 section of the Yaoundé-Douala highway on the dynamics of the surrounding natural environment. To achieve this methodology deployed was based on three axes: the description of the initial state of the natural environment, the evaluation of the dynamics of the surrounding natural environments following the implementation of this section and finally the development of mitigation measures. The description of the initial state of the natural environments was developed through documentary research; the evaluation of the dynamics of the environments was mainly done by direct observations in the field and satellite image processing using mapping software such as: Erdas Imagine, Quantum-GIS and ARC-GIS. This assessment includes vegetation, surface runoff, slope and soil dynamics, and wildlife. Vegetation dynamics were obtained by Landsat 2011, 2014, 2020 image processing, and supplemented by field verification campaigns. Surface flow data were obtained during the site explorations and mapped using the Open Street Map database. The description of soil profiles and the installation of sediment traps made it possible to collect soil data. Wildlife data were collected through field transects and surveys. At the end of these analyses, it appears that the earthworks have led to the modification of the initial landscape of the area, the loss of soil by stripping the motorway right-of-way, the accentuation of the phenomenon of erosion of bare surfaces, the upheaval of the soil profile. From a hydrological point of view, we note the deviation of watercourses and the modification of water flows, leading to a variation in the regime of certain rivers. As far as fauna and flora are concerned, the fragmentation of faunal habitat and the extinction of certain species have been noted. Similarly, the construction of this section has led to the loss of a large area of dense forest. We went from 7939.26 ha in 2011 to 6789 ha in 2020, a total decrease of 49.10% in 9 years or 5.45% per year. In the end, several realistic mitigation measures such as the vegetation of embankments, the creation and restoration of habitats for biodiversity, and the regular maintenance of riverbeds and banks were proposed. The aim is to reduce or even compensate for the impacts on the natural environment after the construction of this section.