Temporal Analysis of Land Use Changes in River Segura Basin using Remote Sensing. Implications on Desertification

Land use change is a dynamic process that affects heavily to different environmental processes. In this work, a GIS application is designed to analyse land use changes from landsat imagery since 1976 to 2007, a period with important socioeconomic and land use changes in River Segura Basin. This work describes the methodology used to obtain a yearly series of land cover maps of the Demarcacion Hidrografica del Segura (River Segura basin in South East Spain). In order to analyze this great amount of information for a large (more than 18,000 km2) and heterogeneous area, a unified methodology has been developed. It has been used a supervised classification improved by a previous not supervised classification using both spectral (4 or 6 landsat solar spectrum bands depending on the sensor available, MSS or TM, ETM) and two textural variables. The last ones were obtained estimating the semivariogram frunction from the albedo and NDVI layers. Having used two images from different seasons, the total number of variables included in the classification is 12 or 16 depending on the year. Preliminary results show a reduction of the surfaces with traditional dry crop uses and the important increase of irrigation lands during the first half of the 1980s decade. The increase in bare soil areas also reflects the abandonment of traditional crops. Finally, it has been observed an increase in urban areas attributable to demographic trends.