Today, many wealthy countries are able to mitigate, to some degree, their risk of delta flooding through vulnerability-reducing investments, but a new model suggests that this mitigation may not be sustainable in the long-term.
Ultimately, wealthy countries could be feeling the strain of floods to a similar degree as developing countries.
To calculate a given delta population's risk of flooding, Zachary Tessler and colleagues accounted for the population's probability of a damage-producing event, how the population's exposure to these hazards may change over time due to changing climate variables, and the population's vulnerability to these adverse events; this latter factor, the authors argue, is strongly influenced by the wealth of the delta's country since high GDP is a good proxy for financial capacity to mitigate the impact of flooding, from household to region-wide scales.
The researchers applied these calculations to 48 major coastal deltas, spanning a range of climate and socioeconomic contexts, with a total estimated current population of more than 340 million. Even though deltas in wealthier countries, such as the Mississippi and Rhine deltas, had similar probability of flooding events and rates of exposure over time compared to some other deltas, their resulting risk levels were much more stable, with risk trends among the lowest of all the deltas in the study.
Four decades of coastal land and wetland loss in the Mississippi River Delta, as observed by Landsat (USGS/NASA Landsat Program). Credit: Zachary Tessler. Data: USGS/NASA Landsat Program
However, when the researchers re-calculated the risks over time taking into account long-term rising infrastructure costs, these deltas had the greatest increases in vulnerability. The authors say investments that manage the drivers behind human-caused delta degradation, rather than its symptoms, will be necessary to sustain deltas in the long-term.
Citation: "Profiling risk and sustainability in coastal deltas of the world," Z.D. Tessler, C.J. Vörösmarty, C.J. Vörösmarty, M. Grossberg, I. Gladkova, H. Aizenman, J. Syvitski, E. Foufoula-Georgiou, Science