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Impact of climate change on river ecosystems

Monday 21 May 2018

Rivers can take decade to recover from storm floods, research study finds.

FLOODING often benefits river estuaries and basins by washing rich sediments downstream.

But frequent storm floods, fuelled by climate change, can impact fragile river ecosystems beyond recovery, according to a study by researchers from Hull, Aberystwyth and Salford.

Research undertaken in South Africa's Kruger National Park by the three universities and AECOM used laser survey technology (LiDAR) from an aircraft to measure the impacts of cyclone-driven extreme floods in 2000 and 2012 on the park’s rivers.

'Rhino' river

Kruger game reserve has global significance for its habitats and wildlife, which includes leopards, civets, eagles, buffalo and both black and white rhinos.

The LiDAR data was used to create accurate digital models of the river bed, and through comparisons with pre-2012 flood data, the researchers were able to map detailed spatial patterns of erosion and deposition.

Dr David Milan,principal investigator from the University of Hull, who worked with Dr Neil Entwistle and Dr George Heritage at the University of Salford, said: "We were primarily interested in trying to understand how these large bedrock-influenced river channels respond to large floods. From comparing 2012 and 2004, we calculated that the 2012 event alone removed almost 1.25 million tonnes of sediment from the river bed.

"We also found that patches of mature riparian (riverbank) forest that survived larger floods in 2000 were removed by the 2012 events. There is a suggestion that the frequency of large flood events is increasing due to climate change and our analysis of river channel morphology for a 50 km length of the Sabie River shows us that these rivers need time span longer than a decade to recover.”


Looking ahead, they conclude that the likelihood of more frequent floods will see sediment and vegetation stripped from the river channel, leaving a more barren environment with less habitat value.

"Continued progressive loss of habitat diversity will fundamentally, and for all intents and purposes irreversibly, alter our riverine landscapes and this will be accompanied by a catastrophic loss of species unable to adapt to the new environments,” they said.

These results have significance for bedrock-influenced rivers in other dryland areas globally, and the team suggest that conservationists need to work alongside geomorphologists to look at ways in which dryland river habitats can be best managed into the future.

The findings were published in the Geological Society of America Bulletin.

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Gareth Hollyman, Senior Press & PR Officer (Science)

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