Résumé:
The Tell of Oran has always been threatened by erratic rains in stormy character, which combined with deforestation important cause severe erosion. These soils are increasingly degraded and sediment from the erosion contribute to siltation of dams. To determine the rainfall erosivity in time and space and soil erodibility, a methodological approach was used with a sample of 11 rainfall stations that are located throughout the Tell Oran. Three test areas were chosen in clay and marl, to identify areas sensitive substrates to water erosion.
The index values range from 5 to Fournier for the station at 17 for Saida Station Ghazaouet. The index values range from 24 to Arnoldus for the station of El-Aricha and 50 for the station Mostaganem.
The application of the alternative formula for calculating the factor of aggression climate characterized the study sites from 40 to El-Aricha and 70 Mostaganem according Rango-Arnoldus and between 28 and 49 for Relizane and Mostaganem according Roose (1981).
The development cards rainfall erosivity through the Surfer 9.0 software to predict and guide the identification of areas of priority interventions for the conservation of soil against the aggressiveness of rainfall where the risk of erosion is potentially high. It appears spatially, the rainfall erosivity increases from south to north of the Tell of Oran.
Laboratory analysis of soil samples and marl was used to analyze the distribution of the sensitivity of the test areas at risk of erosion. This has led to the identification of substrates most at risk from water erosion.
The correspondence analysis (AFC) has helped us to characterize the sensitivity of samples to the erodibility of the substrate:
- The compact and blue marl soils are brown calcareous Calcimagnesian moderately erodible - The light green marl, yellowish-green of the mouth of Cheliff, gray, brown, light green (Oued Mina watershed), soil isohumic nature and vertic vertic soil isohumic blackened gray are highly erodible. - The blue marl soils and alluvial slightly evolved very erodible. This study is a preliminary step to any development of appropriate erosion control.
