The impact of flooding depends more on societal change than climate change
By Roger Pielke
A fascinating new paper just out by Antonia Sebastian, of Texas A&M University, and colleagues in the journal Environmental Research Letters looks at the relative contributions of urban development and climate change to the massive flooding in Houston caused by Hurricane Harvey in 2017. The international team of authors finds that development since 1900 is far more important to observed flooding than is climate change, leading to important policy implications.
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More generally however, the WMO assessment was less confident that an increase in precipitation in hurricanes has been detected more broadly, concluding, “the author team had low confidence that anthropogenic influence specifically on hurricane precipitation rates has been detected.” This low confidence is consistent with recent empirical research which has not found strong evidence to support claims of an overall increase in hurricane rainfall or flooding due to climate change.
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If we consider the authors estimates of uncertainty, societal change had an independent effect on Hurricane Harvey peak discharge of between ~110% and ~500% greater than climate change, and on overall flood volumes, a 1,200% to 6,800% greater effect. Clearly, these are not small differences. Societal change has a huge impact on how floods change over time.
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The authors explain, “urban development has led to a loss in adaptive capacity in the watershed, decreasing the ability of the region’s watersheds to accommodate increases in extreme rainfall due to climate change, and that even with reservoirs and channel modifications intended to provide regional flood reductions, climate change and urbanization have led to net increases in peak flows.” It is thus not sufficient to focus on climate change to the exclusion of development: “attention should be paid to where development might be expected to occur and the combined effects of both development and climate change should be analyzed.”
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