Amphan (pronounced as UM-PHUN) which means sky in Thai is the only other “super-cyclone” to have hit northeastern India since Bhola super cyclone in 1971. AMPHAN crossed Digha (West Bengal) and Hatiya Islands (Bangladesh) and went across to the Sundarbans between 16.30 & 18.30 hrs IST of 20th May with a wind speed of 260 kmph. This powerful cyclone prompted an immediate evacuation of 3 million residents from Odisha and West Bengal owing to the vulnerability of the deltas. Assessing the atrocity of the cyclone, it was enlisted as a category 5 cyclone which includes the deadliest ones. Originating from relatively dry air, the inner ring of Amphan which is called an eyewall contained powerful winds, resulting in heavy downpour. The intense kinetic energy of Amphan thrusted huge amounts of water into several creeks and estuaries in the world’s largest delta. The cyclone intensified rapidly within a very short duration, true to the predictions of IMD. This has been argued by many scientists to be caused by global warming.
The cyclone hit at the confluence of India and Bangladesh situated at the apex of Bay of Bengal which has a historical record of deadly storms. The shape of this coastal area and the bathymetric slope of the ocean floor had a catalytic effect resulting in heightened storm surge flood. Amphan with its 15 to 18 feet (five-six meters) storm surge capacity inundated numerous low-lying areas of South and North 24 parganas in the Sundarbans. The damages accrued by the Sundarbans is catastrophic owing to it being an ecological hotspot with diverse flora and fauna. The entire assessment of storm-surge damage is yet to come to the fore front but it has surely pushed flood water extensively into Sundarbans. It has also increased onshore winds because of counterclockwise circulation and forward speed of the storm. So far, only the impacts of wind speed have been felt and witnessed; the impact of storm-surge could be unimaginably deadly. The inundation of Sundarbans and its impacts will be revealed to us gradually only after a considerable lapse of time and intensive research.
The figure given below is an estimation of the inundation extent of the storm-surge height for Amphan conducted by India’s National Centre for Ocean Information Services (INCOIS) at 0030Z (6 am IST) Tuesday, May 19, 2020. The ground reports as well as this estimation makes it clear that most parts of Sundarbans have been inundated which will linger for a week or so. There have also been several reports of collapse of mud embankments due to the storm-surge which also brings about risks of encroaching waters during high tides until the reconstruction of the embankments.
The above hypothetical flood map found that a 5-meter storm surge inundation can submerge more than 75% of the Sundarbans. Further increase in storm surge will have far-reaching socio-economic and ecological implications. Croplands and settlements are likely to be more affected by the incursion of seawater due to storm surge. Likewise, the mixing of seawater with the coastal wetlands will have a deleterious impact on the biodiversity of the Sundarban coast. Nearly 70,000 people have already been displaced due to storm surge impacts in the last 15 years. Some of the farmlands have been left fallow for more than a decade after cyclone Aila in 2009 due to inundation by seawater.
The recent deadliest Tropical Cyclone in Bengal delta
Bengal delta has witnessed extreme tropical cyclones quite regularly damaging livelihood and mangrove plants. The cyclones have a tendency to return after almost two years. Bengal delta is one of the most storm-surge prone areas. 26 out of the 35 world’s total deadliest cyclones occurred in Bay of Bengal. According to the records, 27% of deaths due to tropical cyclones in the world have happened in India in the past two centuries. In the past all cyclonic storms that have hit this densely populated delta have claimed thousands of lives and displaced several thousands. The deadliest storm in world history, the Bhola Cyclone of 1970, killed an estimated 300,000 to 500,000 when it made landfall in Bangladesh, bringing a storm surge estimated at up to 10.4 meters (34 feet) to the coast. The 1991 Bangladesh cyclone, one of the most powerful tropical cyclones ever recorded in the basin, caused a 6.1 m (20 ft) storm surge, which inundated the coastline, causing at least 138,866 deaths. A series of cyclones over the following decades have left thousands dead and caused severe damage to life, both human and nature.
The storm surge height of Aila Cyclone (2009) was 2-3 m above tide levels, experienced along the coasts of West Bengal and the adjoining areas of Bangladesh. In 2015 cyclone Komen was accompanied by a storm surge of 1 to 2 m (3.3 to 6.6 ft) that affected the Sundarbans in Bangladesh. Last year in 2019 tropical cyclones occurred in Bengal delta was about 1-2 metre height above astronomical tide very likely to inundate low-lying areas of South and North 24 Parganas.
Field photographs of inundation of a river Jetty used by the villagers in Brajaballavpur, Sundarban (Source: Author)
Long term Impact of Amphan
Unlike the Indian Ocean which is unlikely to have tropical cyclones, those originating in the shallow, warm waters of Bay of Bengal lead to catastrophic results. This is because of the dearth of outlets for letting out the pent-up intensities of the storm and resulting in tumultuous landfall. Compared to its predecessor Aila (2009), Amphan had its landfall during low tide reducing its impact to some extent; the contrary would have been more disastrous. The Sundarban lying at the apex of the Bay of Bengal is under constant threat of catastrophic storm surge flood. It is characterized by two inflow and outflow tidal water systems and a tidal height range between 3.5 and 5 m. As per the reports of World Bank in 2014 around 2000 deaths occurred in every cyclonic disaster on an average during 1971–2010.
With respect to Amphan a more devastating storm surge hit areas such as Bhangar-1 (block of South 24 Parganas district in West Bengal) with five to six meters high waves inundating up-to 17 kilometers not just from the coast but also from the rivers and creeks that meet the coast. It also inundated Basirhat block of north 24 parganas situated far (more than 25km) from the coast reaching up-to Diamond harbor and Kolkata with a storm-surge height of two -three meters.
In addition to the explicit damages done by the storm, there are some implicit impacts which will be realized in the long-term such as damaged crops, death of marine ecosystems mainly fishes reared in fresh water ponds and infertility of agricultural lands. The ultimate result adds up to a complete economic downfall, lack of self-employment and aggravated poverty. Sundarbans is entirely dependent on agriculture and pisciculture owing to the availability of fresh water. The inclusion of salt water due to storm-surge inundation impacts these two occupations adversely. History bears testimony to this fact with the example of Aila. Agricultural sector has been heavily affected post Alia 2009 and most of the agricultural land is lying fallow till date and led to massive external migration from the deltas. For those who have returned to their homes due to the COVID pandemic. they are now in no-man’s land. Unfortunately, the damage caused by Amphan is so massive that their hopes of survival in their homelands seem futile. Why such inundations occur in the Sundarbans is a matter of grave concern. I see a few reasons behind it. Even after cyclone Aila less attention has been given to construct earthen embankments and those existing small muddy ones is incapable of resisting powerful cyclonic surges. After Aila caused devastation there should have been intense mangrove plantation along the edges of the deltas which however did not happen. Besides, these inundated waters take a long time to recede in absence of proper drainage facilities and damaged embankments. This might also be the root cause for several water borne diseases in the coming days.
Salinity level also increases due to high inundation of the croplands and settlements making agricultural area unproductive. Further, mixing of sea water with the swamp will have deleterious impact on the biodiversity of the region. Long term impacts have been recognized after the occurrence of storm surge in Sundarbans. Fish production has declined significantly rendering many families jobless. All these major effects of storm surge inundation by super cyclone Amphan are likely to increase posing serious threats to the Sundarban community in future.
Historical evidences point to the regular occurrences of tropical cyclone affecting the Sundarbans. Therefore, it becomes imperative to take some precautionary measures to combat such catastrophes in the coming future. Thus, the infrastructural facilities and road network, embankment maintenance are effective management strategies for reducing vulnerability for any further cyclonic storm in this region. It is equally important to establish community infrastructures such as cyclone and flood shelters and improve early warning systems.
Sahana, M., & Sajjad, H. (2019). Vulnerability to storm surge flood using remote sensing and GIS techniques: A study on Sundarban Biosphere Reserve, India. Remote Sensing Applications: Society and Environment, 13, 106-120.
Sahana, M., Rehman, S., Sajjad, H., & Hong, H. (2020). Exploring effectiveness of frequency ratio and support vector machine models in storm surge flood susceptibility assessment: A study of Sundarban Biosphere Reserve, India. Catena, 189, 104450.
This article was compiled by Mehebub Sahana, Research Associate, School of Environment, Education and Development, The University of Manchester, UK.