Long-term hydro-morphological changes in rivers: a case study

Over time, river hydro-morphological changes cause net aggradation or degradation in bed cross-sections. The presence of sediments in the flowing water as suspended or bed loads, as well as modifications to flow characteristics like velocity and discharge, are the main causes of these alterations. This study examined long-term hydro-morphological changes over 21 years (1982-2003) in the third Egyptian Nile River reach using bathymetric and hydrological data together with numerical simulation. The aims were to track the hydro-morphological changes, including aggradation and degradation, check the ability of HEC-RAS to determine the water surface profile, and check sections of different zones for navigation. It was found that most of the reach under study suffered degradation in the 21-year study period, with net volumes ranging between 8 and 779 m(3)/m; the water surface profile calculated using HEC-RAS matched well with the measured one, the zone located between km 526 and km 534 changed from safe to unsafe for navigation, and the zone located between km 397 and km 385 changed from unsafe to safe for navigation.