Md. Emdadul Haque Badsha :
Govt. of Bangladesh is spending huge amount of hard-earned money to control flood, river bank erosion and to increase depth of navigational channels but people of this poor country are getting poor benefit . We got a lot of very good experience of increasing depth of river Jamuna-Brahmaputra, the Ganges-Padma, Meghna, Surma and Kushiyara from time immemorial ( from British period) by Bandalling and vessels/ships/steamers could ply safely during dry season in those alluvial and meandering rivers. Bandals are much cheaper method as compared with dredging option to provide required flow depth for safe navigation. Dredging in alluvial rivers like Jamuna-Surma-Kushiyara-Padma/Ganges are not sustainable even for one season. Towards the development of sustainable solution to maintain the navigability, BANDALs or combination of Bandals and dredging may provide the desired solution. Channel depth could be increased 8 to 10 ft by Bandalling.
To minimize these sufferings based on the working principles of BANDALs, an idea is developed so that it can be used to stabilize rivers’ courses for long term basis in a step by step manner. River flows are suddenly disturbed by Spur-dyke-Like structures and consequently their responses are big against such interventions. Therefore water courses cannot be stabilized for long term basis.
The output of the research for the stabilization of river courses can solve the problems of Bangladesh that is more or less inherent due to the complex geographical location at the lower riparian of the catchment. From experimental and theoretical analyses, it is found that BANDALs are capable for flow diversion towards the main channel leading to deep navigational channel formation.
On the other hand flow velocities are reduced near the river bank lines that ensure bank protection. In addition to this, the local scours around these structures are much less than it is the case of impermeable Groins. Therefore Bandals would be less expensive solution over conventional methods. Another important feature of Bandal is that the lateral interventions can be extended gradually that can be possible using conventional structures, such as Groins, Revetments.
IWFM of BUET, IWM of BWDB, RRI, experts of Japan, India and the old experienced Officers of CPD, BIWTA are in the same opinion that to save money and to control flood, river bank erosion and to increase depth of main channels BANDALLING is very essential.
(Md. Emdadul Haque Badsha, River Researcher & former Director of BIWTA; e-mail- emdadulbadsha@ yahoo.com)
