HIGHLIGHTS ON HIGH FLOOD EFFECTS ON RIVER NILE

摘要

The flood is a natural phenomenon defined as relatively high flow or stage in a river markedly higher than the usual. It occurs often quite frequently in almost all rivers in the world as a result of a variety of causes. Aswan High Dam (AHD) represents a safeguard for Egypt against high and low floods for more than thirty years. However, Egypt has experienced many high floods during the past few years; examples of them were the floods of 1988, 1998 and 2000. In these floods, the Ministry of Water Resources and Irrigation (MWRI) had to release more discharge downstream the dam to manage the flood and to verify the dam operation restrictions in terms of (water level upstream the dam in the first of Aug. =175.00 m). These releases caused many troubles for human properties and habitations especially in the area of encroachment. In addition, many other side effects on the river behavior, such as aggradations, degradation, bank erosion and many areas were been subjected to inundation. These releases also, indicate some adverse effects on free surface drains. The main purpose of this paper is to introduce the main feature of 1998 flood as an example of high floods. Water surface profiles in critical reaches especially the most downstream reaches are investigated. The reach located between Assiut and Delta Barrages is selected for this investigation. 1 -D Mathematical model (HEC-RAS) is applied to test the effect of increasing the release downstream AHD by applying different scenarios. For each scenario, the water level is predicted, its effect on bank erosion, land inundations, and free drains are analyzed and evaluated. Finally, the study introduces some lessons learned from this flood as well as some recommendations for new flood strategy to manage and limit flood hazards. In addition, some protection and mitigation methods to reduce the potential of floods are also produced.