الاسباب الطبيعية لكوارث نهر القاش : دراسة حالة مدينة كسلا

Abstract

ABSTRACT Flood disasters are considered as major disasters in the Sudan and Kassala city is one of important cities that has been continuously affected by this type of disaster by flood of Gash over it. This study has been carried out for the river and its basin from natural and human perspective; then studying the river, its basin, its length and width sectors and its annual, monthly and daily water discharges and its speed its energy and its deposits represented by the delta and inside the channel, then studying the floods phenomenon, its recurrences its timing and its river and its areas of its effects and its explanation, and the most important factors leading to it. Then the flood irrigation system and its effect on deposits taking place in the river channel. The research concluded that the causes of the disasters are rn Kassala area due to the bad river discharge in the river channel in Kassala city which is caused by the narrow river channel and inability of the river to widen its chamiel or deeper it in order to increase its discharge ability and this is due to the permanent building on the bridge at Kassala city and the continuous increase in the level of the river base in the delta because of the annual deposits on it and the effect of this on increasing deposition in the river channel. Also the increase in deposits and stone chips in the river channel is due to uncontrolled removal of plant cover around the river channel south of Kassala city and quarrying and cutting stones and gypsum which used , to form a level of local base for the river south of Kassala city and its removal lead to hewing or cutting behind the area which lead to the increase of transported materials. The research concluded that the treatment of this phenomenon lies in changing the site of agriculture area in the delta which is to irrigate to the lower party of the delta in order that the base of the river is lowered and also its discharge area; and this will lead to increase of the river ability to discharge the river channel area in Kassala area, by deeping the channel or expanding it and paying attention to and protection it and plant cover in the river's basin area and around it, and reduction of transported material by establishing a local level for the river basin south of Kassala city by rebuilding using strong materials (cement, Gravel) which reduces the cutting ability of the river south of Kassala until the amount of materials causing deposition is reduced.