Flooding occasions are a main hazard worldwide. According to a 2024 Moody’s report, greater than 2.3 billion persons are uncovered to flooding yearly. In India, greater than 600 million persons are in danger of coastal or inland flooding. However, there’s a lack of complete information on susceptible communities’ flood publicity danger, particularly in the Global South.
A brand new examine has tried to bridge precisely this hole by analysing satellite tv for pc pictures of casual settlements or slum dwellings in 129 low- and middle-income international locations and evaluating them with maps of 343 well-documented large-scale floods.
The examine discovered that India has the world’s largest number of slum dwellers dwelling in susceptible settlements in floodplains — over 158 million, greater than the inhabitants of Russia — with most of them concentrated in the naturally flood-prone delta of the Ganga river.
The largest concentrations and largest numbers of such persons are in South Asian international locations; northern India leads in absolute numbers, adopted by Indonesia, Bangladesh, and Pakistan. Other notable ‘hotspots’ embrace Rwanda and its neighborhood, northern Morocco, and the coastal areas of Rio de Janeiro.
Overall, in the Global South, 33% of casual settlements, making up round 445 million folks dwelling in 908,077 households inside 67,568 clusters, lie in areas which have already been uncovered to floods. Countries like India and Brazil even have a disproportionately excessive number of floodplain settlements regardless of additionally having suffered many massive floods.
The examine, revealed in Nature Cities in July, highlights the dearth of danger administration methods that prioritise susceptible communities, together with people who have already skilled floods, past population-level approaches.
Risk and settlement
The researchers categorized human settlements as rural, suburban, and concrete, and located that Latin America and the Caribbean had excessive charges of urbanisation (80%), and thus greater than 60% of settlements had been in city areas. In distinction, Sub-Saharan Africa had the bottom charges of urbanisation and almost 63% of casual settlements had been rural. In Sierra Leone and Liberia, casual settlements hosted most of the inhabitants.
In India, on the time of the examine, 40% of slum dwellers resided in city and suburban areas.
People settle in, or are compelled to settle in, floodplains as a result of a mix of components together with entry to jobs, social vulnerability, and monetary constraints. In India and Bangladesh, the low mendacity Gangetic delta and the big nationwide inhabitants contribute to the numbers.
The examine additionally highlighted inequities in entry to assets and thus native responses to flooding. These susceptible residents additionally endure the loss of jobs and entry to companies among the many oblique penalties of floods.
Exposed populations’ vulnerability was discovered to depend upon socioeconomic components like schooling degree and institutional components like flood insurance coverage.
The authors of the examine wrote that each slum-dwellers and non-slum residents stay in floodplains around the globe, however for various causes. In wealthier areas like Europe, subsidised flood insurance coverage premiums in excessive danger areas promotes the desirability of floodplain areas like beachfronts and water views.
Infrastructure like levies additionally exist to guard folks and homes. However, in the Global South, flood zones provide cheaper land and housing, pushing low earnings households into extra susceptible areas.
Data reveal that patterns of casual settlements even have a definite bias in the direction of settling in floodplains, with slum dwellers being 32% extra more likely to settle in a floodplain than outdoors as a result of decrease prices, as evidenced in cities like Mumbai and Jakarta. In truth, the upper the chance of flood, the upper the prospect of folks settling there.
“In cities like Bengaluru, there definitely is a very strong correlation between informal settlements and their vulnerability to flood,” Aysha Jennath, local weather mobility researcher and post-doctoral fellow on the Indian Institute for Human Settlements, Bengaluru, mentioned.
“Flood prone localities are not preferred by large builders for gated communities or IT parks, so those areas are available for migrant workers and informal settlements as they are cheaper.”
Informal settlements in such city areas are usually tin-sheet, tent or tarp housing, with lease paid to house owners via land contractors (“thekedars”).
SDG deadline looms
The researchers specified the necessity to act on flood vulnerability danger for poorer populations because the 2030 deadline for the United Nations’ Agenda for Sustainable Development Goals (SDGs) nears. The objectives number 17, together with eliminating poverty and starvation, availing clear water and sanitation, and taking local weather motion. They apply to all of the UN’s member international locations and deal with susceptible communities.
The examine additionally articulated the significance of taking a human-centric method (as a substitute of location-focused) to enhance insufficient infrastructure.
Data present massive concentrations of settlements in smaller areas, indicating gaps in housing, infrastructure, and primary companies. Often, even gated communities gentrify flood-prone areas, pushing susceptible communities to areas of greater danger exacerbated by failing infrastructure and lack of drainage, Jennath mentioned.
“Real estate plays a huge role in how these informal settlements come up.”
Finally, the researchers additionally mentioned the necessity for the federal government to collaborate with communities as a substitute of banking solely on conventional catastrophe preparedness. Skill enchancment in areas like sanitation, waste administration, and putting in drainage methods may improve the resilience to not simply floods but additionally different dangers like infectious illness, whereas offering jobs.
“These data-driven insights highlight the disproportionate flood exposure faced by slum dwellers in the Global South and underscore the need for just and equitable flood adaptation management,” they wrote.
The findings are additionally a proof-of-concept for utilizing machine studying, which might course of massive portions of information, to analyse satellite tv for pc imagery and extract nuanced insights, like socioeconomic information embedded in inhabitants densities. As a follow-up, the authors have mentioned they plan to review timewise processes akin to slum growth, local weather change, and human migration to successfully predict future flood danger.
Sandhya Ramesh is a contract science journalist.
