The plain of Lower Cheliff knows a very active space-time dynamics of land cover and land use. We used Remote-Sensing to detect and study these changes during the three last decades. The digital analysis of the satellite imagery corresponding to the years 1988,1992,2000,2001 and 2005 showed the importance of the seasonal effect on the extension and the density of the vegetable cover which is under the narrow dependence of pluviometry. Other factors also intervene on this vegetation such as; the salinity and the hydromorphy which can constitute according to the zones and the seasons factors that limit the natural or agricultural development of the plant. The extension of the urban areas did not save the arable lands which are often most fertile and the least salted. This evolution was very fast between the years 1988 and 2000 following the massive rural migration of the population which has occurred during this period.