The HAD impacts, especially the changes to the river hydraulic geometry (width, depth, slope and channel pattern) are the main concern of scientists and engineers. These changes are indirect relation with the imposed discharges and sedimentation processes. In order to understand and predict future changes and responses due to future releases and human intervention, it is necessary to understand the existing changes and development over space and time. This paper evaluates and analysis the measurements of a series of field survey used to investigate morphological changes for the S-shaped reach located downstream of Benha City from Km 69.220 to Km 76.080 downstream of Delta Barrages Damietta Branch of about 6.860 km length, twenty two cross section were studied. These cross sections were selected to illustrate the hydraulic geometry changes as well as aggradations and degradation processes over the studied years. These sections indicate some of the changes that have occurred during these series that may reflect the overall changes to Damietta branch. Different hydraulic parameters such as width, depth and area of these cross sections are calculated under a fixed datum. This datum is defined as the water level corresponding to maximum and minimum discharges of 62.1 and 9.90 Mm³/day respectively. Since the change in the geometrical properties of the curved river parts are non-uniformly distributed over the cross section. Therefore, mean depths of the cross sections are calculated by dividing the effective cross section area under the fixed datum over the corresponding cross section width. The variation iin the mean depth indicates either aggradation or degradation trend. The ability of the main channel to tolerate navigation is also tested. The study concluded that overall aggradations are formed especially at the inner curves of both bends as well as a significant degradation along the outer curves. The study proposed some training structures to strength the main channel |
