The construction of sustainable road and highway networks in the world, despite numerous feasibility, pre-feasibility and execution studies, are always confronted with the demands and vagaries of foreseeable and unforeseeable natural disasters. Studying cyclones, earthquakes, fracturing and landslide zones along roads is therefore a challenge for the sustainability of these infrastructures. In many countries around the world, the methods generally used for these studies are not only expensive and time-consuming, but also the results obtained are not always efficient. This work examines whether Landsat 8 (with a high cloud level) and SRTM data can be used in both equatorial and coastal Central Africa zones to produce relevant mapping, locating fracture and landslide zones, in order to contribute not only to a better road layout at lower cost and in a relatively short time, but also to a better prevention of geological disasters that may occur on its network. To this end, a map of the main road network was produced and validated with field data, as well as the maps of the main unstable slopes, faults and fractures zones intersecting the road or highway network. These approaches are useful for sustainable planning, management, monitoring and extension of roads worldwide, especially in Central Africa.

Nowadays, modelling groundwater potential zones (GWPZs) based on scientific principles and modern techniques is a major challenge for scientists around the world. This challenge is even greater in arid and semi-arid areas. Unmanned aerial vehicles (UAVs), geographic information systems (GISs), and multi-criteria decision making (MCDM) are modern techniques that have been applied in various fields, especially in groundwater exploration. This study attempts to apply a workflow for modelling the GWPZs using UAV technology, GIS, and MCDM in semi-arid areas. An aerial survey provided a high-resolution DEM of 4 cm. Six influencing factors, including elevation model, drainage density, lineament density, slope, flood zone, and topographic wetness index, were considered to delineate the GWPZs. Four classes of groundwater potential were identified, namely high (4.64%), moderate (23.74%), low (18.2%), and very low (53.42%). Three validation methods, namely borehole yield data, receiver operating characteristic area under the curve (ROC-AUC), and principal component analysis (PCA), were used and gave accuracies of 82.14%, 65.4%, and 72.49%, respectively. These validations indicate a satisfactory accuracy and justify the effectiveness of the approach. The mapping of GWPZs in semi-arid areas is very important for the availability and planning of water resources management and for sustainable development.

The construction of sustainable road and highway networks in the world, despite numerous feasibility, pre-feasibility and execution studies, are always confronted with the demands and vagaries of foreseeable and unforeseeable natural disasters. Studying cyclones, earthquakes, fracturing and landslide zones along roads is therefore a challenge for the sustainability of these infrastructures. In many countries around the world, the methods generally used for these studies are not only expensive and time-consuming, but the results obtained are not always efficient. This work examines whether Landsat 8 (with a high cloud level) and SRTM data can be used in both equatorial and coastal Central Africa zones to produce relevant mapping, locating fracture and landslide zones, in order to contribute not only to better road layout at lower cost and in a relatively short time, but also to better prevention of geological disasters that may occur on its network. To this end, a map of the main road network was produced and validated with field data, as well as the maps of the main unstable slopes, faults and fractures zones intersecting the road or highway network. These approaches are useful for sustainable planning, management, monitoring and extension of roads worldwide especially, in Central Africa.

The search for and knowledge of the best conditions for anchoring the foundations of certain structures such as bridges, tunnels and quays in sedimentary estuaries is a challenge, for both scientists in general and engineers in particular. Indeed, wharves are structures that receive a lot of stresses and therefore require anchoring to avoid tilting and to guarantee their stability during service. This work, based on the analysis of data from seismic refraction methods, mechanical soundings and laboratory tests, characterises the terrain of the Wouri estuary in Central Africa. The objective is to determine and present the subsurface layers encountered as well as their characteristics, in order to define the best conditions for anchoring the foundations to ensure the stability of the quays to be built there. The seismic refraction campaign shows that the study area is relatively heterogeneous over the first 25 m, with velocities measured in the range 1520–1750 m/s; modulated in two distinct ranges, between 1520–1580 m/s characteristic of mud and loose sediments (alternating layers of clay, sand, loose silt) and the range 1580–1750 m/s corresponding to the signature of sandy-silty or compact clays. The mechanical tests show sedimentary soils, with alternating layers of sandy clay and clayey sand over the 42 m drilled, loose over the first 30 m in the bank area and over the first 15 m in the canal or dredge area, with a limit pressure of less than 1 MPa. Similarly, the soil samples taken and tested in the laboratory show that the soils are clayey over the first 30 metres, plastic and liquid with respect to their water content, respectively, below and above the liquidity limits, confirming their loose character. The results of seismic refraction, mechanical soundings and laboratory tests show that, in estuarine areas characterised by alternating sandy clay and clayey sand, there are not always hard formations in the first 25 metres of depth but, from a depth of 30 m, the soils become moderately compact and begin to form an anchoring layer sufficient to guarantee the stability of the quays against earth pressure forces.