Abstract:
This research deals with the morphological analysis of Jamuna river using
finite element method. RMA2, a hydrodynamic model and SED2D, a sediment
transport model, have been used to simulate the morphology of the Jamuna. Models
have been applied using SMS (Surface-water Modeling System) environment, which
gives the pre- and post- processing options for input and output data.
The finite element mesh has been developed using LANDSAT image
of the Iih November 2000. Initial bed elevations for the nodes of the mesh have been
composed from the scattered survey data of April 2001 by BIWT A. Once the mesh
and bathymetry have been obtained, the models are ready thereby to incorporate
boundary conditions, initial conditions and material properties.
The hydrodynamic model developed in this study has been satisfactorily
calibrated and validated against the observed water surface elevations at Aricha for
2001 and 2002, respectively. Sediment model has also been calibrated using measured
bathymetry by BIWTA with the simulated bathymetry of 23rd August 2001. The
model has been validated with the measured bathymetry of November 2002 and
November 2003. Sediment rates at Baruria have been generated from the SED2D
model and compared with the FAP-24 data (FAP, 1996).
Results reveal that erosion takes place in the outer bend of the meandering
Eastern anabranch. In Western ana branch, severe deposition has been observed near
the confluence due to backwater effect of Jamuna-Ganges flow. Velocity reduction in
the confluence significantly diminishes their sediment transport capacity, and hence
inducing deposition. Three morphological years have shown much similar type of
erosion/deposition patterns, which occur mainly in August and September of each
year. An investigation, using surveyed bathymetries from 1996 to 2003, shows that
the 1998 flood initiates drastic changes in its Western anabranch near Nagarbari,
which indeed may have an impact on the shifting of flow more towards left bank at
Naradaha. These observations of measured data are further substantiated by the results
obtained from the present simulation models.
To find a suitable location for ferry ghat and also for a sustainable navigable
channel, three options have been investigated. Existence of a deep pocket near
Naradaha motivates this study to take those options and among them Option 2, which
is a dredging option in the upstream channel connecting upper segment of the deep
pocket, has appear to show very little deposition compared to other options. Thus the
option in question presents a prospective alternative for developing a sustainable ferry
route.
