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Archer, L.,
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Hawker, L.,
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Collings, T.,
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Sear, D.
A new study has been published in Environmental Research Letters revealing the population exposed to flood risk across the Small Island Developing States (SIDS). Led by Leanne Archer at the University of Bristol, the research paper was also contributed to by a number of Fathomers including Professor Jeff Neal, Professor Paul Bates, Dr Natalie LordTom Collings and Dr Niall Quinn.
What are SIDS – Small Island Developing States?
The Small Island Developing States (SIDS) are a UN-defined group of island nations and territories widely recognized as particularly at risk of the impacts of climate change, while contributing very little to it. Despite this awareness, the size of the population exposed to flooding had not been calculated. This study, led by the University of Bristol’s Leanne Archer, estimates for the first time the population exposure to coastal and inland flood hazard for current and future climate scenarios across all 57 SIDS.
Climate change is amplifying the risk of flooding across SIDS by influencing the magnitude and/or frequency of extreme precipitation, river flow, and coastal storm surge events. But how many people does this amplified risk impact? In this study, population estimates for all 57 SIDS are calculated for the first time, to provide a consistent methodology for calculating exposure to flood hazard at the 100-year return period, for the present day and in the future against three climate scenarios: SSP1-2.6, SSP2-4.5 and SSP5-8.5. For the first time, this paper also considers both coastal and inland flooding, to provide exposure estimates across all three flood perils – pluvial, fluvial and coastal.
- Present day exposure: 19.5% of the SIDS population, or approximately 8.5 million people, are currently exposed to the 1-in-100 year flood hazard. In three SIDS countries– Guyana, Tuvalu and the Bahamas – more than 60% of their population is exposed to the 100-year flood hazard.
- Inland vs coastal flooding: Due to the tendency for coastal regions to be densely populated, storm surge events pose a significant risk to the SIDS population. However, this research shows that inland flooding is the primary driver, accounting for 81% of the population exposure. Previous studies have only focused on coastal flooding, representing a significant underestimation of exposure.
- Climate change impact: Under future climate change scenarios, flood exposure is projected to increase to 21% under the lower emissions scenario SSP1-2.6 (i.e. an additional 650,000 people) and 23% for the pessimistic high emissions scenario SSP5-8.5 (an additional 1,500,000).
- Consistent exposure: The rank and order of the most exposed populations remains relatively consistent across different climate change scenarios, suggesting the need for adaptation measures for these states, regardless of future climate uncertainties. Populations estimated to experience the biggest rise in flood exposure under SSP5-8.5 include Belize, Turks and Caicos Islands, and the Maldives.
- Lack of correlation: Notably, the flood hazard (i.e. the extent of land inundated) and population exposure are not always strongly correlated.
The analysis was completed using Fathom’s Global Flood Map, a high-resolution global hydrodynamic flood model, overlaid with the WorldPop population dataset with population totals adjusted to 2020 UN estimates. The inclusion of direct measures of flood hazard and exposure is essential to adequately reduce loss and damage from flooding in the SIDS.
Interested in learning more about Fathom’s Global Flood Map?
Read the full research paper, Population exposure to flooding in Small Island Developing States under climate change by Archer et al. in Environmental Research Letters.
The research in this paper has garnered media attention – check it out in: