Managerial response to sea level rise in the tidal estuaries of the Indian Sundarbans: a geomorphological approach

Abstract

Tidal estuaries constrained by embankments in the Sundarbans have failed to respond to a .1 m sea level rise over the past 100 years since their construction. This paper shows that this has led to a disequilibrium morphology leading to channel erosion that has undermined embankments, causing mass failure, breaching and subsequent flooding during surge events. Predicted future sea level rise will exacerbate this trend and managed realignment of embankments will be needed to accommodate it. Management practices have, however, modified this underlying process of erosion. The increasing practice of severing tributary channels from the main channel using flap sluices to create freshwater storage ponds has, in many cases, reduced tidal flow in the main channels so that they are not only accreting rather than eroding, but capable of accommodating future sea level rise without erosion. In contrast, the rapid spread of salt water aquaculture in the Sundarbans, flooding previous paddy land, has led to an increase in tidal discharge and accelerated erosion of the embankments in estuary channels conveying water to the ponds. This paper concludes that existing management practices may have a more significant impact on flooding in the Sundarban than the predicted sea level rise due to global warming.

Interplay of Physical, Chemical and Biological Components in Estuarine Ecosystem with Special Reference to Sundarbans, India

“…Perhaps the most important data required is for tidal and surge information, however such data are almost entirely absent at the moment (Bhattacharyya et al, 2011 It was observed that tidal range along the Sundarbans estuaries vary from place to place within the estuary. On an average, tidal fluctuation in Sundarbans estuary is around 5 meters depending on the lunar cycle, as is evident from the Figure. 2.…”

Compositional data analysis of Holocene sediments from the West Bengal Sundarbans, India: Geochemical proxies for grain-size variability in a delta environment

“…These channels reflect an almost exclusively tidal-105 driven geomorphology, with sediments and discharge from the main G-B rivers no longer 106 entering the western delta front (Allison, 1998b;Bhattacharyya et al, 2013). 107…”

Managing water-related risks in the West Bengal Sundarbans: policy alternatives and institutions

“…In addition to eustatic SLR, relative SLR in the Indian Sundarbans is influenced primarily by land subsidence, e.g. from auto-compaction, tectonic activity and anthropogenic processes, including groundwater withdrawals (Bhattacharyya et al, 2013). Further information on land subsidence contributing to SLR, as well as challenges resulting from the limited relevant data in the Sundarbans, is given in the supplemental material.…”

“…Some of the technical work performed for the World Bank study has appeared in the peer-reviewed literature (e.g. Bhattacharyya, Pethick, & Sarma, 2013;Biller & Sanchez-Triana, 2013), but most of it has not.…”