Global warming is giving rise to accelerated sea-level rise. Sundarban being a subsiding delta such rate of sea-level rise shows compounded effect which is much more than the eustatic average rate. Sundarban delta is facing gradual inundation of islands on one hand and a gradual increase of surface water salinity on the other. Effect of rising salinity has of late became apparent even at the upstream of river Hoogly within the stretch of Kolkata where during last seven years true mangrove species like Sonneratia caseolaris has started appearing along with other back mangals. IPCC findings indicates a higher rate of rise of global average temperature since the year 2000 resulting in greater acceleration of rate of sea level rise. The nature’s signature of such rise in salinity in the tidal Hoogly river is the appearance of mangroves within its Kolkata stretch on both the banks. Further, it is apprehended to jeopardise the ground water of the thickly populated Kolkata city, which calls for immediate massive rainwater harvesting to delay such saline incursion.