Land use/ land cover change detection and quantification : a case study in eastern Sudan

Abstract: Remote sensing with high temporal resolution images has become a very strong tool for monitoring the Land use/Land cover (LULC) changes. Sudan has long been experiencing intense LULC changes. These LULC changes have resulted in widespread land degradation. The conversion of natural woodland and forest is still the main source for agricultural expansion in Sudan. Rainfed mechanized farming (RMF) is not new in Sudan, it started in the early 1940s near Gadarif state the eastern Sudan. The current study examines the temporal and spatial extent of LULC changes from 1972 to 2006 in Gadarif state. This area is famous for its sorghum and sesame production. A periori defined seven LULC classes in the classification scheme were water bodies, RMF, mixed rangeland, irrigated land, dense forest, sparse forest and settlement. Individual classifications were employed using the both supervised and unsupervised classification. Iterative Self Organizing Data Analysis (ISODATA) was used to see the cluster of different classes in the images. Maximum likelihood classifier (MLC) was used in the LULC classification of the individual images. The accuracy assessment of image classification was checked by aerial photographs and high resolution images from Google maps. The overall accuracy of LULC maps for each period (1984 and 2006) range from 86, 88 and kappa statistics are from 0.84 and 0.86 respectively. For change detection post-classification technique was applied. Image pairs of consecutives dates were compared by overlaying the LULC maps and cross- tabulating the LULC statistics. The amount of conversion from sparse forest to mixed range occurred as large as 14247 km2 during the first period (1972-1984) and 1060 km2 during the second period (1984-2006). The conversions to RM have mainly been occurred from mixed range land and sparse forest as large as 4063 km2, 4701 km2 during the first period (1972- 1984) and 18743 km2, 5449 km2 respectively during the second period (1984-2006) of study. Conversions to RMF occurred at high amounts. A total of 29615 km2 area changed from mixed rangeland and sparse forest to RMF. Settlement area increased in the second period from 23 km2 to 123 km2. The LULC change study plays an important role for better understanding of land utilization and sustainable development of the region.