Etude De Surcreusement Des Pistes Rurales Ou Forestières, Sur Le Plateau Des Cataractes: Cas Des Routes Koubola - Kibossi Et Koubola – Bissinza (République Du Congo)

This article investigates the track overdeepening, a rare type of degradation that turns roads into trenches. He carried on two rural tracks south of Brazzaville, in the Pool Department, in the Republic of Congo, quantifying the phenomenon by the cubing method; describes the processes of formation and evolution through in situ observations; Highlights the vulnerability of the environment through the quantification of some variables representing its physical characteristics and, with the ArcGis 10.1 software, maps the phenomenon for a geo-referenced location of the main forms. Estimated at 13,724 tons of land loss on the first axis and 14,424 tons on the second road, the overcrowding is one of the forms of dramatic erosion of agricultural or forest tracks in the study area. Triggered by the bad treatment of the ruts, the processes of installation and evolution of this type of gully are favored by the sensitivity of the tracks themselves marked by apparent densities which vary between 1.7 and 1.8 g / centimeter cubic, with an average porosity (about 30%) and that of the geological formations in the clayey-clay ensemble with a high clay content (over 30%) which favors the process of overdeepening marked by the verticality or almost of the boundary walls. The mean of the erosivity index R is estimated at 6000 MJ.mm/ha.h.an, with an average annual height of 1400 mm characterizing the climatic aggressiveness of the zone and the slopes which reach and exceed the 25% , Are all aggravating factors. The prediction of this phenomenon requires a change in the method of treatment of the ruts and the stabilization of the forms already constituted and active, by that of the rolling surface and especially the walls by bio-mechanical methods

Etude Des Facteurs De Risques De Dégradation Par L’érosion Hydrique Du Tronçon Routier Dolisie/Pointe-Noire Au Sud Du Congo Brazzaville Et Évaluation Des Aménagements Antiérosifs

Située dans l’extrême sud-ouest du Congo, la route nationale Pointe- Noire / Brazzaville traverse, dans son tronçon Dolisie- Pointe Noire, long de 164 km, la chaine de montagne du Mayombe et les plateaux côtiers, deux unités géomorphologiques aux caractéristiques morpho-structurales très sensibles qui l’exposent aux risques de dégradation par l’érosion hydrique. La présente étude vise l’identification et l’analyse des facteurs de la vulnérabilité de cet ouvrage et l’évaluation des aménagements antiérosifs. Les observations et mesures de terrain ainsi que les analyses de laboratoire montrent que la vulnérabilité de cet axe routier face aux risques d’érosion est liée, d’une part, à la présence généralisée des fortes pentes, à la texture argileuse du Mayombe, favorable aux ruissellements et sableuse des plateaux côtiers, favorable aux affouillements des roches, à l’érosivité très élevée des pluies et l’érodibilité élevée des formations pédologiques et , d’autre part aux actions anthropiques. 6 ans après sa mise en exploitation, le dispositif antiérosif bien qu’efficace dans son ensemble, affiche par endroits, quelques faiblesses qui exigent un renforcement de l’entretien. La route est déjà affectée par un début de dégradation qui se manifeste par des écroulements, des glissements de terrain, des griffures et rigoles le long des parois abruptes qui bordent la route sur les terrasses et des tranchées. La dégradation se manifeste aussi par des ravinements qui engendrent déjà des grosses pertes en terre. Located in the extreme south-west of the Congo, the 164-km-long national road Pointe-Noire / Brazzaville crosses the Mayombe mountain range and the coastal plateaux, two geomorphological units to the south, in its 164- kilometer Dolisie-Pointe Noire stretch. morpho-structural very sensitive to exposing the risk of degradation by water erosion. The present study on the identification and analysis of the vulnerability factors of this book and the evaluation of the erosion control arrangements. Observations and field measurements as well as laboratory analyzes have also revealed a part, with the widespread presence of steep slopes, the clay texture of Mayombe, favorable to runoff and sandy coastal plateaus, conducive to scouring rocks, the very high erosivity of the rains and the high erodibility of the soil formations and, on the other hand, the anthropogenic actions. 6 years after its start-up, the anti-erosion device of its effectiveness as a whole, displays in places, some weaknesses requiring a strengthening of maintenance. The road is already affected by a beginning of degradation that is manifested by collapses, landslides, scratches and gullies of steep walls that line the road on the terraces and trenches. The degradation is also manifested by the ravages that already generate large losses in soil

Histoire et dynamique actuelle des cirques d'érosion du littoral d'Afrique centrale. Une étude de cas : Les ciques d'érosion du littoral ponténégrin (Congo)

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