Application Remote; Sensing; G.I.S.To Monitor ;Land; Cover Basin ;River Atbara –Sudan

Abstract

This study is an attempt to investigate land use and land cover changes along the upper basin of the River Atbara in Sudan and their environmental consequences using remote sensing and the Geographical Information System (GIS) techniques. In order to achieve that, land use and land cover activities are classified into eleven categories (Table 1). Satellite images for the study area, in three different periods, were collected and analyzed to detect the changes in land cover, and accordingly three maps of land use and land cover were produced (Maps No. 9,10 and11), by using the computer soft ware ILWIS (International land and water Information System), as well as three maps of land cover changes were also produced (Maps No. 12,13 and14). The changes in extent and percentage of the different land cover categories were calculated for the different periods (1973,1986 and 1996) in (tables 5,6 and 7). The investigation showed that, the area suffers from wide spread changes of land cover and land use change especially in agricultural areas, forest and, range lands. The mechanized rain-fed agriculture had expanded at the expense of rangelands and forests, that led to land degradation by enhancing the soil erosion and consequently the crop yield declined sharply due to the decreased fertility between 1970-1990 (Tables 13 and 14). The investigation also revealed that, despite the shrinking of the rangelands area, the number of the grazing animals continued to increase. These simultaneous changes enhanced the degradation process in the area. Disappearing of some palatable vegetation species and, appearance 98 of undesired species particularly at the north of the area was a good indication for land degradation. Clearance of natural vegetation (forests) also led to appearance of gully erosion in many parts of the area (plate,3). This geomorpholoical process resulted in siltation at the lake of Khashm el-Girba reservoir, accordingly it’s capacity reduced which consequently led to shortage of irrigation water in New Halfa Agricultural Scheme (NHAS), and lessened the electric generation of the dam (Fig. 17). Karablands (Typical badlands ) which lies along the banks of the River Atbara and its tributaries represent a unique phenomenon in the area, therefore it has been investigated thoroughly well in a separate chapter (Chapter 6). After a geomorphological and pedological studies, it appeared that, the karablands were a former in-land lake formed by the River Atbara which ended at that time (about 7000 years approximately), at Goz Rajab village. The river deposited its load in that lake, by time the River Atbara reached The River Nile and made its way in its former deposits, due to climatic change towards drier periods which enhanced erosional processes that formed the karablands .