Diagnosis and Qualitative Estimation of the Hydric Erosion in Watershed of Talangaï (Brazzaville) by the Application of Geographical Information System (GIS)

Abstract

This research work exposes the results of our study about the cartographic and the qualitative estimation of the hydric erosion of the watershed of talangaï (Brazzaville) following the PAP/RAC approach, tele detection’s data and the geographical information system in order to elaborate thematic cards by enlightening erosion phenomenon. In this watershed of talangaï, this phenomenon of erosion became recurrent and causes more and more spectacular and worrings. As a matter of fact, except climatic aspects of the study zone, this watershed is characterized by a large irregularity of precipitations, of steep slope, and a weak vegetable coverage; which renders it very vulnerable to the erosion. Thus, after the analysis and the treatment of collected data, from the geographical information system (GIS), the study shows that 65% of zone of study present a weak and average erodibility and 35% of a high and the highest erodibility. Likewise, the descriptive cartography of different forms of erosions shows that ravine surface and the erosion in table-cloth are the most current. Also, the consolidated card of erosion states shows in a qualitative way that soil loss in the zone of study is in relationship with its geomorphology. In short, after combining different cards of principle erosive states, a synthesis has been done producing the consolidated card of these states (Integration approach). All these unfavorable conditions; slopes; geomorphology; erodibility; friability of soils, vegetal covert …), triggering of the catastrophe about erosive phenomenon are fulfilled. Thus, the obtained results allow to identify zones which are the most concerned, and the most vulnerable to hydric erosions.