Soil water erosion is a major aspect of landscape degradation in sub-wet to semi-arid Mediterranean environments. This problem has not been dealt with in detail in Algeria although it affects large areas. The objective of this study is to develop a methodology using remote sensing, the digital terrain model (DTM) and geographic information systems (GIS) to map areas with a risk of water erosion within the territory of Saida province and to produce a risk map that can be used as a reference document by the local authority. The presented methodology consists to incorporate three factors controlling the erosion: slope, material friability and land use. The resulting erosion risk map shows five areas of vulnerability to water erosion: very low, low, moderate, high and very high. Areas with high and very high risk of erosion cover more than 20% of the mountainous area and are consistent with our field observations. The methodology presented in this study can be generalized to all areas of the foothills of the Tellian Atlas, where erosion risks pose a threat to urban areas. This model is a tool to help implement a soil conservation plan in order to organise the measures to be applied and ensure sustainable soil management.

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This work aims to better to know the floral richness of Tell region (Saida, western of Algeria) particular orchid flora. This inventory was started in 2017-2022; It’s based on random samples, in spring and autumn. The surveys directly targeted open areas (Northern Saida). This inventory revealed the presence of 11 orchids including 2 species, 6 subspecies and 2 varieties. The 11 taxa belong to 5 genera: Anacamptis, Dactylorhiza, Himanthoglossum, Orchis and Ophrys. Some taxa are rare, endemic and are protected (threatened) by the IUCN Red List as a near threatened species and/or are endemic and protected in Algeria, rare species in the Tell region. A stationary precision made it possible to know the distribution area of each identified taxon. Due to anthropogenic threats, a strategy to protect habitats seems very urgent.