New research, based on forest fires in Australia, proves there is a significantly higher risk of large-scale flooding when major deforestation has occurred in catchment areas.
The chance of large-scale flooding in a specific catchment area can increase by as much as 700% if widespread deforestation has occurred.
That is the finding of a new paper by academics who analysed decades of flooding data from regions in Australia which frequently suffer forest fires.
The loss of forest canopy has long been claimed to increase the risk of flooding, but actually proving the direct link has been difficult since the impact of other factors such as changing climate are hard to exclude.
But a team of researchers, led by Professor Ashish Sharma from UNSW Sydney, have now confirmed the correlation and determined there is a very significant increase in the risk of flooding if forest canopies are removed from catchment areas.
“What we have shown is that the probability changes from a one-in-64 year flood event, to a one-in-eight year flood event if there has been deforestation.
“So we can say there is an eight-fold increase in the likelihood of there being a flood,” says Prof. Sharma, from UNSW’s School of Civil and Environmental Engineering.
“Another way of thinking about it is to imagine there being 64 different forested catchments. In any single year, the most extreme climate would cause the highest flood in one of these 64 catchments.
“But according to our analysis of the data, if there was major deforestation, then in the same year, the same flood would be exceeded in eight of the 64 catchments.
“Deforestation and mega forest fires under climate change are happening all around the world, so this is a very important topic.”
Implications for the future
Prof. Sharma hopes the research will be taken on board by anyone involved in the process of man-made deforestation, given the devastating impact flooding can have on human populations who may be living in areas at risk.
“The data is collected from south-east Australia, but we see no reason why the conclusion does not apply in the same way anywhere else where forest canopy is being removed,” he says.
“Our main message is that extensive deforestation has a significant increase in flood risk. If deforestation is happening, then there should be strong consideration for planning rules or regulations regarding habitats downstream to reduce the enhanced danger they will face from flooding.
Read the full report at nature.com.