Millions in danger of delta disaster

There are rising fears that  climate change and extreme weather is placing 31 million people across the world in danger of facing a real threat of devastating flooding.

Researchers from Indiana University have issued a study which warns the world’s deltas are becoming a major cause for concern with no real data ion just how many millions are now living on these deltas.

The researchers warn that the threat from flooding, cyclones, and climate change is growing but the study is the first which has attempted to identify not only the threat but also the level of resilience.

The team, from the university’s Department of Earth and Atmospheric Sciences’, analysis shows that river deltas occupy 0.5 percent of the earth’s land surface, yet they contain 4.5 percent of the global population—a total of 339 million people. Because river deltas form at the ocean at or below sea level, they are highly prone to storm surges, which are expected to occur more frequently due to climate change-fuelled sea-level rise and coastal flooding.

In the study, IU researchers analysed these geographic regions, which include cities like New Orleans, Bangkok, and Shanghai, using a new global dataset to determine how many people live on river deltas, how many are vulnerable to a 100-year storm surge event, and the ability of the deltas to naturally mitigate impacts of climate change.

“River deltas present special challenges for predicting coastal floods that deserve more attention in discussions about the future impacts of climate change,” said IU Distinguished Professor of Anthropology Eduardo Brondizio, a co-author of the study who has been working with rural and urban communities in the Amazon delta for 3 decades. “Our estimates are likely a minimum because the storm surge and flooding models do not account for the compound interactions of the climate impacts, deficient infrastructure, and high population density.”

“To date, no one has successfully quantified the global population on river deltas and assessed the cumulative impacts from climate change,” said Douglas Edmonds, the Malcolm and Sylvia Boyce Chair in the Department of Earth and Atmospheric Sciences and lead author on the study. “Since river deltas have long been recognized as hotspots of population growth, and with increasing impacts from climate change, we realized we needed to properly quantify what the cumulative risks are in river deltas.”

In addition to the threat of flooding, many of the residents in river deltas are low-income and experience water, soil, and air pollution, poor and subnormal housing infrastructure, and limited access to public services. According to the study, of the 339 million people living on deltas throughout the world, 31 million of these people are living in the 100-year storm surge floodplains. To make matters worse, 92 percent of the 31 million live in developing or least-developed economies. As a result, some of the most disadvantaged populations are among the most at-risk to the impacts of climate change.

“These communities are already dealing with health risks, lack of sanitation and services, poverty, and exposure to flooding and other environmental risks. Climate change is exacerbating all of these issues and creating more impacts,”  Mr Brondizio.

To conduct their study, the researchers created a global dataset of delta populations and areas, aggregating 2,174 delta locations. They then cross-referenced the dataset with a land population count to determine how many people were living in the deltas. To determine the natural mitigation capacity of the deltas, researchers looked at the volume of incoming sediment deposited by rivers and other waterways flowing out to sea. The volume of incoming sediment was compared to the relative area of the delta to determine if the delta would be considered sediment starved and thus unable to naturally mitigate flooding.

“To effectively prepare for more intense future coastal flooding, we need to reframe it as a problem that disproportionately impacts people on river deltas in developing and least-developed economies,” added Mr Edmonds. “We need better models for the climate impacts that are capable of stimulating compound flooding in densely populated areas so that exposure and risk can be mapped to more accurately assess risk and vulnerability.”

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