Tipaimukh dam
Photo: A.M.Ahad / Driknews
There are many earthquakes in this world which were generated due to water load from a manmade reservoir. Moreover this region is one of the seismically active zones of the world (we all are aware if it); any large earthquake would be a big threat to the dam as there are geological evidences that the Shilong Earthquake propelled large boulders even up to Chhatak area. Any seismic failure will cause a sudden onrush of reservoir water through the Surma-Kushiyara valley and will reach up to Meghna floodplain. Interestingly, there are many ground elevations in upper Meghna valley which are just at sea level. This water will be enough to inundate about 25% area of Bangladesh by 5 ft. This volume of water would be capable to submerge the greater Sylhet district under 10-ft of water. The higher gradient runoff would be of extremely high-energy flow at least up to the downstream region of both Surma and Kushiyara rivers. This dam will cause price hike of cement and aggregates (construction stone and sand) in Bangladesh and thus increase the construction cost throughout the country. Because the Surma River (also Kushiyara) will lose its normal navigational draft (required water depth for navigation of river vessels/boats etc.) and bulk transportation of cement from Chatak Cement and Lafarge-Surma Cement factories will be disrupted. There will not be any active water transportation system during the lean period in a few years after construction of the dam if we do not plan for an alternative. The landscape of Surma and Meghna floodplains will be changed and might look like present day Rajshahi region. In the lean period many parts of the greater Sylhet district will turn into semi-desert. The agriculture land will be prone to differential erosion due to unpredictable flood pattern during the monsoon. The Bangladesh Water Board might work out surface water modelling for predicting other unknown affects and work for reduction of associated risks. I believe there are many engineering and technological solutions for assessment and monitoring risks from such a large geo-morphological modification in a complex geological environment. I understand scientists and technologists from both Bangladesh and India are aware of these and experts are thinking on the issue.
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