Abstract:
A physical model facility has been developed near building for the dept of Water Resources
Engineering, BUET, Dhaka. This was a long felt need of the department for hydraulic
model studies. Previously this facility was available only at River Research Institute (RRI),
Faridpur. The model studies at RRI concentrate on field problems and are not available for
academic research. After developing the mode~ the aim was to prepare a physical be~
model of Jamuna river for the reach length between Kazirhat and Ganges-Jamuna
confluence to study the morphological response of the river due to groyne. The secondary
purpose of the study was also to get an insight about the suitable location for the ferry ghat
at Natibpur, which is under constant threat of erosion and deposition.
The sand bed in the physical model facility is 45.73m (150 feet) long and 10.67 m (35 feet)
wide. It is filled up with 0.81m (2 feet 8 inch) depth of sand of Dso equal to 0.18mm. Two
Rehbock weirs are incorporated as measuring devices in the system, one at the upstream
end and the other at the re-circulating canal. Three gauge points on the western side to
measure depth of water in the sand bed and one manually operated instrument carriage
made of steel truss are also installed over the bed for data acquisition. The water supply in
the system is developed with a storage pool capacity of 210 m3 with three centrifugal
pumps (total capacity 150 lis) with control valves.
After the completion of physical model facility, the braided channel of Kazirhat- Ganges
Jamuna confluence area, which is about 16 km long and 4 km wide, was represented on
this model. The horizontal and vertical scale ratios are 1:400 and 1:60 respectively. For this
purpose the river charts were collected from BIWT A.
Five representative discharges covering wide ranges of river flow were selected. By
studying the flow lines and the morphological changes (mainly scour and siltation) the
location of one groyne was identified around Natibpur. The model study showed that by
providing a groyne at Natibpur the area dis of the ferry ghat upto 1.5 km could be protected
at moderately high flow. The study also showed that the bank line from Natibpur upto the
Ganges-Jamuna confluence near Aricha could be protected from scour by constructing four
normal groynes in series with a gap of 800m c/c approximately.
