From: Wilson Da Silva, University of New South Wales
Published August 16, 2017 08:15 AM

Urban floods intensifying, countryside drying up

Drier soils and reduced water flow in rural areas but more intense rainfall that overwhelms infrastructure and causes flooding and stormwater overflow in urban centres. That’s the finding of an exhaustive global analysis of the world’s river systems by UNSW researchers.

The study by engineers at UNSW, which appears in the latest issue of the journal Nature Scientific Reports, explored how rising local temperatures due to climate change might be affecting river flows. It reviewed data collected from more than 43,000 rainfall stations and 5,300 river monitoring sites across 160 countries.

As expected, it found warmer temperatures lead to more intense storms: a warming atmosphere means warmer air, and warmer air can store more moisture. So when the rains do come, there is a lot more water in the air to fall, and rainfall is more intense.

But there has been a growing puzzle: why is flooding not increasing at the same rate as the higher rainfall?

The answer turned out to be the other facet of rising temperatures: more evaporation from moist soils – which are needed in rural areas to sustain vegetation and livestock – is causing them to become drier before any new rain occurs. Meanwhile, in small catchments and urban areas where there are limited expanses of soil to capture and retain moisture, the intense downpours become equally intense floods, overwhelming stormwater infrastructure and disrupting life.

Continue reading at University of New South Wales

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