Flooding occurs when water is in excess and can no longer be evacuated normally. The nature of the soil has been identified as one of the major causes of flooding, hence this study aimed is to show the influence of the physico-chemical properties of the soil on the recurrence of flooding in the Mbo plain. Four soil profiles were carried out on the alluviums according to the altitudes. These profiles were described and undisturbed soil samples were taken. Then, measurements of the infiltration rate of water in the soil by the Porchet method were carried out in sixteen sites. Finally, soil samples taken by auger and core sampling were studied in the laboratory. Physico-chemical parameters such as grain size, porosity, moisture, pH, compactness and organic matter were determined. Infiltration tests carried out in situ using the Porchet method revealed a hydraulic conductivity between 10 -5 and 10 -7 m/s, characteristic of a semi-permeable soil. This low value of permeability results from the morpho-structural arrangement and the chemical composition of the soils of the plain. These soils are hydromorphic, which means that they are constantly flooded and temporarily waterlogged.They are more or less sandy-clay on the surface, and very clayey at depth, generally from 25 cm. The very clayey soils at the base considerably slow down infiltration and act as a real barrier layer that prevents water from infiltrating, resulting to intense runoff. These soils are very porous and compact with a fairly high water content of up to 71 %. This work allows us to conclude on the role of intrinsic soil properties on the genesis of floods in lowland areas. As in many plains in Africa and in the world, the nature of the soil in the Mbo plain is a natural predisposing factor to flood risks. The methods used can be applied in areas with the same characteristics as the Mbo Plain.
The Southern Escarpment of the Bamileke Plateaux (SEBP) is an area frequently affected by mass movements. An analysis of the susceptibility of these hazards is important in order to better understand these mountain processes. Field campaigns as well as the exploitation of satellite images in the laboratory have made it possible to inventory all sites subject to mass movements in the region. The region is affected by landslides, block falls and subsidence. Landslides are the most frequent hazard in the region. These hazards are regulated by about 10 natural and anthropogenic factors which include lithology, geomorphology, anthropogenic action, soil, proximity to roads, proximity to watercourses, density of watercourses, slope, direction of slopes, and curvature of slopes. The steepest slopes are between 27 and 90°, the most important slopes are oriented Nord-West. The curvature of the slopes shows zero, convex and concave slopes. The soils in the area are ferralitic, humus-bearing and hydromorphic. The land use shows bare soil and cultivated soil. The geomorphology shows altitudes ˃ 1319m, the highest stream densities range from 183-293m and constitute the significant proximities causing instabilities. In relation to the different classes of river proximity, the highest river proximities are ˃120m. The highest road proximities are ˃ 50m relative to the other road proximity classes. The geological formations that dominate the area are basalts, mylonites, granites gneisses and charnokites. These factors were mapped and the different maps were overlaid to obtain a mass movement susceptibility map of the study area. This map shows that 16.95% represent low probability areas, 43.39% represent moderate probability areas, 29.77% represent high probability areas and 9.89% represent very high probability areas. The majority of mass movements, especially landslides, are located in the high probability areas.
Flooding occurs when water is in excess and can no longer be evacuated normally. The nature of the soil has been identified as one of the major causes of flooding, hence this study aimed is to show the influence of the physico-chemical properties of the soil on the recurrence of flooding in the Mbo plain. Four soil profiles were carried out on the alluviums according to the altitudes. These profiles were described and undisturbed soil samples were taken. Then, measurements of the infiltration rate of water in the soil by the Porchet method were carried out in sixteen sites. Finally, soil samples taken by auger and core sampling were studied in the laboratory. Physico-chemical parameters such as grain size, porosity, moisture, pH, compactness and organic matter were determined. Infiltration tests carried out in situ using the Porchet method revealed a hydraulic conductivity between 10−5 and 10−7 m/s, characteristic of a semi-permeable soil. This low value of permeability results from the morpho-structural arrangement and the chemical composition of the soils of the plain. These soils are hydromorphic, which means that they are constantly flooded and temporarily waterlogged. They are more or less sandy-clay on the surface, and very clayey at depth, generally from 25 cm. The very clayey soils at the base considerably slow down infiltration and act as a real barrier layer that prevents water from infiltrating, resulting to intense runoff. These soils are very porous and compact with a fairly high water content of up to 71%. This work allows us to conclude on the role of intrinsic soil properties on the genesis of floods in lowland areas. As in many plains in Africa and in the world, the nature of the soil in the Mbo plain is a natural predisposing factor to flood risks. The methods used can be applied in areas with the same characteristics as the Mbo Plain.
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