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2 September, 2019 10:50:15 AM


Dredging must be sustainable and eco-friendly

Both capital and maintenance dredging have undergone improvements in recent times
Syed Mehdi Momin

Bangabandhu Sheikh Mujibur Rahman had a special flair for anecdotes. He had a intensive background of personal experiences deeply rooted in the soil of the delta country.

While talking to relatives in his Dhanmondi Number 32 residence just a year or so before his tragic assassination he was reminiscing about his childhood days.  "When I was a boy, used to play football on the banks of the river with the Britishers from the dredger company. Then the war came, Second World War, and the dredgers were taken away to make barges for the Burma campaign. They never came back. Now there is no river where I used to play, only silt; and we have huge floods every year.” He was deeply worried about this annual phenomenon of flooding and was keen to solve the problems associated with it. The onus is now on the powers that be to deal with the perennial problem of flooding and siltation.
Year after year Bangladesh is forced to spend a huge amount on dredging its main rivers to ensure navigability. If extensive dredging of rivers is regularly carried out  in major rivers, the navigability will obviously increase. How this dredging should be done in a planned way to make it sustainable and environment friendly. People of this riverine delta have learnt to expect annual flooding. Floods are both a boon and a bane. The harmful effects of flooding are quite visible triggering the loss of life and property.

Much like the ancient annual flooding of the Nile River and the Mississippi River Delta siltation in the United States that supported the rich harvests of crop, flooding in Bangladesh also helps the agricultural land to retain and regain its fertility. However an unnaturally large accumulation of silt that stays in that particular area of that river. Rainstorms may also transport these soils into other water sources. Sensitive marine life and freshwater fish may be affected by suspended silt in their native waters. Filter feeders of rivers are literally "choked up" by silt-laden waters. Waterways and irrigation canals could also become affected in their functions by silt accumulations. Other harmful impacts of siltation are human health concerns, the loss of wetlands, coastline alterations, and even changes in fish migratory patterns.

To make dredging more cohesive and strategic, the government has finalised a draft policy on river dredging and the management of dredged materials. Reportedly, dredged materials are often dumped haphazardly resulting in ecological devastation.

Under the draft policy, the departments concerned would have to deposit dredged materials about 300 metres away from the riverbanks. The local administrations would not be able to allow unplanned sand extraction from rivers without proper alignment with the appropriate authority.Siltation as indicated earlier is a double edged sword. When floods take place in the country, silt falls on agricultural lands and enhances soil fertility.

Clay carried by floodwater also plays an important role in building fertile land. The 57 transboundary rivers that flow through Bangladesh carry a huge volume of silt, which replenishes the soil every year and is a key to its fertility. As the rivers flood and erode land along one bank, they deposit silt on the other. Cultivators in this part of the world for eons have known how to benefit from this.

As the leading Bangladeshi water expert Prof. Dr. Ainun Nishat has said in the recent decades floodwaters have been carrying sand rather than silt, leaving behind barren soil and accelerating erosion throughout the year. And irregular sedimentation is rapidly increasing riverbank erosion. The dams that hold back the silt are being built or planned in other countries. So Bangladesh cannot deal with the situation on its own. It needs to convince upstream countries to cooperate more closely on integrated management of common river basins. Silt is also a curse for navigation along the rivers. It also means that riverbeds rise with silt and the rivers flood more easily after heavy rainfall or if a lot of water is released from dams upstream. On increase of sedimentation changes the behaviour and ecology of the river, affecting the lives and livelihoods of local people.

So much concerns for the problems. The solution, many experts have said, is dredging. As a matter of fact dredging is believed to be the ‘only’ solution to bring navigability of waterways, especially in the river channels. Dredging in Bangladesh becomes necessary to protect coastal erosion through raising embankments alongside river banks. Sustainability issues are of growing concern in the world, as the effects of human activities on the planet become more visible. The environmental impact of dredging activities has been a point of discussion for a long period.

Over recent years more emphasis is put on sustainability by different stakeholders in answer to the climate change effects like pollution, shortage of resources, stress on ecosystems and as a result an imbalance in the total system.

The authorities must combine sustainability requirements with the ever increasing demands on dredging applications.

There was a time when dredging of rivers used to be rather simple activity. The procedure was one of simply pumping out the liquid sediments accumulating in riverbeds and releasing the muddy water into other localities. Now, though the process is way more complicated. And capital and maintenance dredging have undergone dynamic improvements in recent times with the introduction of high-tech trailing suction hopper dredgers and the mighty cutter suctions.  However, dredging, though giving the lost current and navigability back to rivers, is now entangled with hazards. At the fore are the adverse environmental impacts including loss of bio-diversity, improper land reclamation and prolonged disruptions to use of waterways. Unplanned or poorly planned and implemented dredging is destroying aquatic life. Ineffectual dredging is the major cause of shrinking of rivers in this country.

Reclaiming of land after dredging is another serious issue. There are vested interest groups who grab land thus reclaimed. Consequently there is little chance of increasing agricultural lands. The authorities must ensure that dredging does not become an exercise in futility.  

The writer is Senior Assistant Editor of The Independent


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Published by the Editor on behalf of Independent Publications Limited at Media Printers, 446/H, Tejgaon I/A, Dhaka-1215.
Editorial, News & Commercial Offices : Beximco Media Complex, 149-150 Tejgaon I/A, Dhaka-1208, Bangladesh. GPO Box No. 934, Dhaka-1000.

Editor : M. Shamsur Rahman
Published by the Editor on behalf of Independent Publications Limited at Media Printers, 446/H, Tejgaon I/A, Dhaka-1215.
Editorial, News & Commercial Offices : Beximco Media Complex, 149-150 Tejgaon I/A, Dhaka-1208, Bangladesh. GPO Box No. 934, Dhaka-1000.

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