Tracking Morphological Change Trends along River Nile in Egypt Using Hydrological Data Analysis

Document Type : Original Article

Authors

1 Nile Research Institute, National Water Research Center, Ministry of Water Resources and Irrigation

2 Civil Engineering Department, Shoubra Faculty of Engineering, Benha University

Abstract

Riverbed morphological changes occur due to water flows. The flow energy dislocates riverbed sediment particles and transports them downstream. Such transport changes the riverbed shape over time causing unrecognized bed degradation and aggradation. Therefore, this study aims to track morphological change trends along Nile River 4th reach over past 50 years using hydrological data analysis to identify the future trends, especially in light of the constantly repeated annual discharge cycle. The 4th reach starts at Assuit Barrages and ends at Delta barrages. Data of 10 years between 1962 and 2010 of daily discharges and corresponding water stages at eight gage stations along the study reach were collected. Another additional annual flow to the reach amounting to 7.5 % of the original flow was considered. Seventy-five stage-discharge rating curves were established for the gage stations. Regression quadratic polynomial formulae were established for the curves and used to determine the water stage "WS" values at the eight gage stations for discharges of 37, 70, 100, 140, and 181 Mm3/d over the ten years. Considering 1962 as a reference year, the WS profiles due to the discharge cases were computed and compared. The WS rise and fall were interpreted as possible riverbed morphological changes. The study revealed aggradation through the reach upstream segment between Maabda and Sheikh Fadl Gages, then severe degradation at the middle segment between Beba and Bani Sweif, then aggradation at the downstream segment between Koraymat and Leithy. Finally, the results were verified by comparison of past and present bathymetries.

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