Bioshield Coast Guard For Eco-Sensitive Zones In Bengal
The government of West Bengal plans to develop an ecologically sustainable and robust ‘bioshield’ along the Sunderbans islands and state’s coastline for strengthening the defense of the whole state as well as Kolkata against catastrophic cyclonic storms like Amphan which are envisaged to rise due to climate variations. The aim is to build an embankment on the east which faces the concave coastline, where there is frequent & high erosion and develop a geotextile cover, plant 36 species of strong mangroves & construct earth embankments.
Mamta Banerjee, CM (Chief Minister) of West Bengal suggested a multi-layer vegetation shield as a cover to safeguard against ingress of saline water, erosion, and storms in coastal Bengal. The previous month, she had formed an expert committee of 24 members, led by Kalyan Rudra, a river professional & chairman of the state pollution control board. The final report by the committee explaining the plan details was recently accepted as the ultimate guide for any work centered in that particular eco-sensitive area by H. K. Diwedi, the chief secretary.
Climate variations have been severely affecting the Bengal delta area, where the sea-level rise is the largest in the world. There has been a 3.6mm increase in the global mean sea level annually between 2006 & 2015. Each year there is a 4mm rise in the sea level off the coast of Bengal. The repercussion of the Sunderbans’ sea level rise is additionally exacerbated because of annual slow land subsidence at 2.9mm. This roughly constitutes an annual sea-level rise of over 6.9mm.
The committee has suggested a multi-layer vegetation shield that is climate-resilient: a 2-layered cover along the river embankments and a three-layered cover along the sea coast in the Bengal delta.
Rudra stated that 36 species of green & blue algae and mangrove associates & mangrove were selected based on their tidal influence, salinity resistance, height, propagation ability, and, resilience. He added that invasive species were omitted and despite the concrete embankment, which is capital-intensive, vegetative shield selectively serves as a wave breaker, besides replenishing the beaches.
The waterways and irrigation department has found 378 vulnerable rivers in West Bengal having an overall length of 559km, out of which, 207 rivers with a total length of 324km have been identified as extremely vulnerable. Most of them are facing the concave banks towards the east, where there is high embankment breaching. Another embankment has been proposed in such areas to reduce the effect of erosion and cyclones.
If the former frontal embankment is situated along the high tide area, the buffer zone between the new & old dykes might ideally be 200m, and be announced as no-construction areas according to the Coastal Zone Regulation, 2019.
Rudra mentioned that additionally, the eroded beaches in the Sunderbans and East Midnapore have become so low and narrow that the wave-breaking areas have shifted closer to land. As there is barely any zone along Sagar Island’s southern front in order to build a proper ‘bioshield’, a man-made off-shore reef barrier has been suggested by professionals from IIT-Madras.
Bioshield Coast Guard