The objectives of this research were to analyze and evaluate the effect of releasing flow discharges
on river meandering in addition to estimating the local scour at 13 bridge piers distributed on 3
bridges located on Rosetta branch. The meandering length was 3.5 Km (from km 145.00 to km
148.50) D.S of El-Roda Gauge at Kafr El-Zayat City. Several sorts of data were collected including
site maps, velocity measurements, bed samples, hydrographic survey data, water levels and
discharges at several years and seasons, as well as visual inspection photos to be used in the
current study. The configurations in bed level, the thalwege line, and the scour holes were
determined by comparing the surveyed entire reach at years 1982, 1998, 2003 and 2006.
Study area was simulated four times by 2-D mathematical model “SMS” using a survey reach at
years 1982, 1998, 2003 and 2006. This was done to estimate the velocities and the water levels for
different discharges at the entire reach. The flow was used as upstream boundary condition and the
water level was used as downstream boundary condition. The model was calibrated and verified
using the field measured velocities.
Two proposed alternatives were suggested and numerically simulated separately. The first
alternative, the outer bends were filled with layers of filter and riprap to level -5.00 m MSL. The second alternative included filling the scour regions to level -5.0 m MSL in additional to dredging the
inner sides of the bends where sedimentation regions were located to level -3.00 m MSL. The two
alternatives were numerically tested under maximum and emergence flows. The results analysis
proved that flow conditions were enhanced and improved under the second alternative when
compared to the first one. Based on the results, layers of filter and riprap were designed to fill the
scour holes. |
