It is estimated that roughly Tk10,000cr worth of stones have been looted from along the Goiyan river basin. This figure could be underestimated and likely calculated based on the construction cost of looted river stones and sand which is very rudimentary. I began wondering about the true cost of such environmental destruction but failed because there are too many things to consider.
The hilly tributary which was until recently famous for “shaada pathor” enters Bangladesh from Meghalaya. It is monsoon driven so water levels can vary up to 10 times depending on the season. The river moves nearly 3,000 tons of sediment yearly down its course, although it is moving much more now that the river bed has been destroyed.
In the immediate surroundings, there are at least 15 endangered plant species and haors with over 200 fish species. They are also a haven for many birds. The ecological significance of haors are immense, they are also RAMSAR protected sites and extremely fertile. Tea garden watersheds also exist in the surroundings and account for about 80% of the tea economy of Bangladesh.
There are also several small holder farmers and fisheries in the area. Overall the entire ecosystem and many economic activities in the area depend on this river channel for fresh water, either directly or through the aquifers it recharges.
These shaada Pathor are no ordinary stones; they represent 20-40 million years of Shillong Plateau erosion. Bangladesh therefore is losing this piece of history dating all the way back to the Miocene era forever.
What does that mean for Sylhet and those around the Goiyan river?
It is important to note that these are just estimates and don’t take into account the effects of climate change or look beyond the immediate surroundings of the mines. Rivers flow and any changes made upstream of a river will have a domino effect downstream all the way to the Bay of Bengal with varying effects along the rivers course.
In five years
Channel incision in the Goiyan increases, causing more variation in water flows eroding the river bank unpredictably. This will lead to reduced water quality and will reduce fish spawning habitats and insect habitats as well as affect alluvial deposits to the haors in the region.
This could reduce fish stocks in the haors by up to 60% depending on the sediment load variation. Lastly, it will be an even bigger blow to any ecological tourism aspirations Sylhet has.
In 10 years
The river course would be altered, it would be wider, deeper and cause more unpredictable flooding in an already flood-prone region, not to mention the loss of infrastructure and agricultural land due to a widening and deepening of the river.
A rough analysis shows this erosion risk up to 50 km downstream from the point of illegal stone extraction, by my estimates everywhere from Jaintiapur through Sylhet Sadar all the way to Chhatak Bazar will have a very different river front.
The removal of these boulders increases the risk of river bank collapse up to 70% in some areas. The risk of landslides in the region also increases, not to mention the increased landslide risk from future earthquakes along the very active Dauki fault.
Lastly, agriculture would be severely affected, the loss of top soil brought about by increased rain (due to climate change) and a wider river channel would mean a lot of the fertile top soil would be easily washed away.
In 20 years
The Goiyan river won’t be able to buffer monsoon rain flow from upstream, which also happens to be the rainiest place on Earth. More sedimentation flows downstream will alter the morphology and water quality of the Surma river and all the rivers it connects to.
The river could alter its course up to 3km west, this would drown tea estates and cause nearly 40% loss in agriculture productivity and change land use patterns across the region.
Merely returning the stones will not mitigate these damages as they deposited here over millions of years.
What do we do now?
It is important for us to focus on mitigating the damage caused as the natural architecture of the region has forever changed. We need to model these geomorphic shifts to understand how to minimize downstream infrastructure and agricultural losses as well as environmental damage.
Nauman Zahur Haque is the Founder & CEO: Mrittika Solutions. Email: [email protected]. Mrittika specializes in climate risk mapping to develop tailored climate action and adaptation plans for businesses.
