Hydraulic Evaluation of River Restoration Using Numerical Modelling Approach

Abstract

It is well recognized that urbanization strongly impacts on the Nile River characteristics. The Nile River has experienced major morphological changes during the past decades. Unplanned human interventions and their activities change the connections between the river channel and its adjacent floodplain as shown at Al Wasta City waterfront which located on the west bank of the Nile River, about 81.50 kilometers south of Cairo, Egypt. The study reach suffered from decreased morphological and ecological diversities resulting from human interventions. The major thrust of this research is the proposition of a new strategic plan for river restoration based on quantitative analysis rather than only qualitative assessment. The main goals of the research are to analyze the historic and present river geomorphic and morphologic characterizations at the study area, develop the hydraulic modeling approach to detect these changes using two dimensional model, and propose and evaluate four restoration alternatives to increase hydraulic efficiency of the river channel. The number of restoration alternatives were identified and were evaluated to find favorable restoration measures to improve the hydrodynamic conditions at the study reach in order to be able to control and sustain the desired water levels, water flow velocity, and hydraulic channel conditions by the removal of sediment deposition (by the dredging process). The two dimensional hydrodynamic model was used to map the flow pattern in the study area and to identify the areas of accelerated sediment deposition. The model results indicated the slight improvement in the values and distribution of water velocities at the western bank of the study reach and secondary channel (khor channel). The third proposal represented the best proposals in terms of the relative efficiency of hydraulic properties. The proposal include the elimination of constraints to river’s natural patterns, and drive river channel to return to the track of natural succession, and keeping a state of hydraulically and morphological balance.