Amid the Covid-19 pandemic, dealing with floods will prove to be a bigger challenge
While the whole world is currently facing difficulties in managing the spread of Covid-19, the ocean and atmosphere have just observed the probability for an onset of La Niña, which is referred to as the cold phase of El Niño-Southern Oscillation (ENSO) cycle. The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central equatorial Pacific. These deviations from normal sea surface temperatures (SSTs) can have large-scale impacts on ocean processes, global weather, and climate.
Therefore, in the wake of the Covid-19 pandemic, many ENSO-sensitive countries may likely face dual disasters. This article reviews the on-going ENSO (particularly La Niña) from the perspective of intensity, onset/duration, and its impacts on seasonal climate variability in Bangladesh. The objective is to provide a La Niña-based advance seasonal climate outlook for dual-disaster preparedness and response planning.
The official NOAA-Climate Prediction Center (CPC)/IRI consensus forecast which was published on May 14, favours ENSO-neutral conditions through the summer and fall, and slightly tilts toward La Niña at the end of the year (Oct–Dec)(~45% chance). This year will then be a year of transition from El Niño to ENSO-neutral to La Niña (note that 2019 was an El Niño year).
This year’s La Niña is particularly important for the disaster management planners as it may further aggravate health disasters and/or complicate the current Covid-19 recovery efforts. Meeting the challenge of dual disasters will be a serious management effort for many countries in the developing world, particularly in Bangladesh.
Bangladesh is normally flooded during any La Niña year (particularly during strong and moderate events) due to the Ganges-Brahmaputra-Meghna (GBM) basin-wide heavy rainfall and high sea level at the estuaries. Observations from historical data reveal that during any strong La Niña year (eg, 1998, 1988) Bangladesh faces catastrophic flooding and approximately 70–100 thousand sq-km are inundated (eg, in 1998 about 100,000 sq-km area was inundated).
In the case of a moderate event, the range of inundations lies between 40–60 thousands sq-km, while a weak event may inundate roughly 40,000 sq-km, which is slightly higher than the normal median flood affected area in Bangladesh (median flood-affected area is 29,000 sq-km).
Besides floods, the chronology of tropical cyclones, since 1960, shows that most of the major cyclones that hit Bangladesh at different periods were during either an El Niño or La Niña event, or a transitioning period from one to the other.
For example, during the transition from a strong El Niño to ENSO-neutral to La Niña in May 2016, tropical cyclone Roanu hit Bangladesh on May 22. 21 people were killed and half a million residents displaced. Tropical cyclone Amphan made landfall on Wednesday (May 20, 2020) lashing coastal areas in India and Bangladesh with ferocious wind and rain. This was the first super cyclone to form in the Bay of Bengal since 1999 (1999 was a strong La Niña year).
Though the wind of Amphan had weakened by the time it struck, it was still classified as a very severe cyclone. Covid-19 and social-distancing measures made mass evacuations more difficult, with shelters unable to be used to full capacity.
Currently, all indications are favourable for a weak La Niña in Sept–December of 2020. As the year advances, the intensity of the event may slightly change to either direction. However, based on the current oceanic and atmospheric conditions, it is unlikely that this year’s La Niña may turn out to be a stronger one, like that of 1988 or 1998.
It is also important to note that the onset of La Niña will be relatively delayed this year (Sept–Oct as opposed to normal onset in April–June), which means that the La Niña-induced rainfall will not occur during the peak monsoon season. This is, in other words, a positive indication that the probability of any severe flooding (like that 1998 or 1988) is virtually nil this year.
Without Covid-19, the impact of this kind of La Niña would be felt with very minimal life and property damage in Bangladesh. However, the current challenge is how to respond to La Niña disasters while managing the Covid-19 pandemic.
We have already seen that Covid-19 disrupted flood responses in Japan, Canada, and other Pacific countries. Improper response to flooding would therefore spread Covid-19 and increase disaster damage, leading to further human losses and economic damage. If Covid-19 measures are overdone, flood response may be inadequate to decrease damage.
Therefore, local organizations and communities should play an important role in these dual disaster management challenges by utilizing scientific knowledge. As the experience of disaster management shows, various organizations, including health and water, should be coordinated to conduct response and mitigation.
The organizations concerned with disaster management, water, humanitarian assistance, and health should provide guidelines and approaches to respond to the dual disasters of Covid-19 coupled with La Niña-related flooding.
Dr Md Rashed Chowdhury is PEAC-Principal Research Scientist at the Joint Institute for Marine and Atmospheric Research of the University of Hawaii, USA. Email: [email protected]