The construction of the Beni-Suef bridge, spanning 550
meters over the Nile River, resulted in sediment accumulation and
hindered navigation. This study investigates the causes of the
morphodynamic changes and explores the impact of dredging as a
mitigation measure through the area which extended
approximately 2.6 kilometers downstream the bridge. A one
dimensional numerical model (HEC-RAS) was employed, utilizing
bathymetric surveyed cross-sections from 1982, 2002, and 2004,
along with discharge data from downstream Assuit Barrage and
water levels from upstream Delta Barrage as boundary inputs. The
model was calibrated and validated using measured water and bed
levels. Sediment properties and bed composition were incorporated
based on samples collected by the Nile Research Institute. Three
distinct sediment load formulas were utilized to identify the most
suitable one for accurately capturing the physical characteristics of
the studied area. After validation, the model was utilized to forecast
cross sections for 10 and 20 years, in case of with and without
dredging scenarios. The dredging approach was aligned with the
navigation requirements in the study region. The study reveals that
the Ackers-White sediment formula showed the closest match with
minimal differences in deposition and erosion compared to other
formulas. Besides, the study area is predominantly experiencing
deposition, which is projected to continue in the future. In addition,
the predicted sediment volumes were concentrated at the beginning
of the study area in both scenarios. The findings indicate also that
most depositions occurred in the initial ten years approaching a
state of morphodynamic equilibrium. Moreover, the results showed
that the dredging reduced rates of sedimentation by 23% and 26%
after 10 and 20 years, respectively, which provide an effective
solution for mitigating sedimentation along the navigation path in
the study area. |
