Climate Change

Embankments, seawalls may increase inundation, costs: New study

Shoreline armouring can increase damages by $723 million for a single flood event

By DTE Staff
Published: Thursday 15 July 2021

Sea-level rise due to climate change has threatened millions of lives and exacerbated infrastructure costs in building embankments and seawalls. These flood-protection constructions, however, heighten the risks of flooding and cost greater financial damages, according to a new report.

"Protection of individual shoreline segments (5 to 75 kilometres) can increase flooding in other areas by as much as 36 million cubic metres and damages by $723 million for a single flood event," the study published in Proceedings of the National Academy of Sciences of the United States of America found.

Researchers from The University of Texas at Arlington and the Stanford Natural Capital Project analysed the flow of floodwater depending on the location of the new seawalls along the San Francisco Bay shoreline in California.

They employed complex mathematical tools to find this correlation as well as the additional costs incurred by flooding events.

The team found the strategies that locally reduce flooding "can increase inundation along other shorelines within the same estuary or bay".

The team's findings can also be applied to other coastal estuaries with low-lying, dense development, such as Texas' Galveston Bay and Chesapeake Bay on the East Coast.

The scientists developed various scenarios to gauge the extent of impact of the flood-protection constructions. "The individual shoreline protection scenarios considered in one of the cases can cause as many as 5,900 additional people to be affected by external flooding," according to the report.

The report also predicted that shoreline armouring will become the most prominent method of checking sea-level rise in the United States. "It is forecast to represent nearly 60 per cent of the roughly $500 billion in US adaptation costs by 2100," the authors wrote in the report.


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