Abstract:
Simulation of sediment transport rate at the river Jamuna and variation of bed level
along the river is carried out by using a two dimensional morphological model. Noncohesive
sediment transport module of Delft 3D Flow is used for the simulation. The
upstream boundary of the model is taken at 30 Km upstream of Bangabandhu
Bridge and downstream boundary is taken at 20 Km downstream of Bangabandhu
Bridge.
Simulation period is taken from April 2010 to December 2012. Simulation is carried
out for hydrodynamic calibration and for sediment transport rates. The cross-sections
are taken at the locations which are vulnerable, such as Subaghacha, Sirajganj,
Jamuna Bridge and also in the upstream near Kazipur and downstream near Chauhali
etc. In the Morphology tab, the morphological scale factor has been set to 8.25 which
extend the 121 days hydrodynamics to about 1000 days of morphological change.
Calibration and validation are carried out against field observations (water level) of
2010 and 2011 respectively. Comparisons between simulated and observed water
level are taken at the Sirajgonj station. The results showed satisfactory agreement
with observed values.
For hydrodynamic and morphological computation, a time series discharge data is
used at the upstream boundary and water level data as downstream boundary.
Observed and simulated bed level elevation of 2010 has been compared and the
comparison showed a very good agreement. After calibration of the model, the net
amount of erosion and deposition along the river reach is computed. Finally, crosssectional
variation of bottom level during the monsoon seasons from 2010 to 2012
has been observed.
Results reveal that erosion takes place in the channel bed and the deposition mainly
takes place to the adjacent char areas and increased its width and area. It is also
evident that the channel has been shifted westwards of the reach due to shifting of the
bank line of the river. Many tributary and distributaries have been appeared due to
progressive erosion. In Sirajgonj, the sediment transport capacity seems to be the
xvii
highest due to higher velocity of flow. The zones of higher velocity has higher
sediment transport capacities therefore occurs more erosion
