Of droughts and flooding rains

New climatalogical research from Monash Uni (below) confirms what many "locals" in rural areas already believed - droughts are often followed by floods, and that 'extreme dries' are associated with 'extreme wets'.

This isn't because more rain is falling, however - it's because of the interaction between the rain that does fall and the other environmental conditions...and, I would add, the social and economic conditions.

In 2003, I spent a year or so studying the 1998 floods in the East Gippsland Shire, focusing in particular on the Tambo Valley, a valley just south of Hotham, in the same general area that this research was conducted. I used the concept of 'vulnerability' to examine the economic, social and environmental root causes of flood disasters, and through a historical analysis found that there was a very clear pattern of drought coinciding with low commodity prices, and being followed by severe flooding. Where fires occurred before rain, the effects would be even worse - what little vegetation remained after years of drought would be further stripped away by fire, and as noted, the black soil would have climatological impacts that would worsen floods.

As I noted in a post a few days ago, the history of my study area showed that when drought coincided with a fall in commodity prices, farmers would avoid de-stocking (because of low-prices), which would result in over-stocking and over-grazing. In addition, their financial constraints would limit their ability to do things like keep rabbits down, fertilise etc. So the state of their farm enterprises - both ecologically and financially - would go deteriorate. When rain finally came, it would fall on the steep hills that characterise the area (and are also found in the Alpine Shire) - these hills would be denuded, the soil compacted, and the rain would run straight off.

Climatological research is obviously vital to emergency management, but it fails to address the social and economic dimensions of vulnerability, which are integral to the environmental dimensions of vulnerability. While the Alpine Shire is likely to be environmentally vulnerable to flooding, individuals and communities in the area are also likely to be socially, psychologically and economically vulnerable. Farmers are already strapped-for-cash due to the drought, and this is likely to have associated impacts on relationships within families, couples and communities. When (or, if you look elsewhere in Australia, the appropriate language might be "if") the rain comes, they're not going to be in the best condition to respond to the costs arising from water damage, nor are they going to be socially and psychologically equipped to bounce back with great ease.

This research points to the need for holistic approaches to emergency management - as environmental conditions that shape people's lives change, so too will their economic and social conditions.

Climate Research at Monash University: Drought and fires trigger worse floods

5 December 2006

It has long been argued that Victoria's weather is growing hotter and drier, now research conducted at Monash University has proved it is getting more extreme.

And with more than 50 fires now blazing throughout the state, it also grows more vulnerable to flooding.

Professor Amanda Lynch, from the Monash Climate Program, has been working with a PhD student, Lee Tryhorn, to establish a database on bushfire and flood events in Victoria. The database records where and when fires have occurred and how significant they were. The same applies to flooding.

"There does seem to be an indication that fires are on the rise across Victoria," Professor Lynch says. "Anecdotally, there are more fires and they are worse than they were in the past. Things have definitely grown drier, the weather has grown warmer and it is more conducive to fires."

But the researchers were surprised to find a link between the rising number of bushfires and an increase in heavy rainfalls and the severity of floods.

"It does seem strange, but it's been found in other parts of the world that while rainfall can be going down, they are still experiencing extreme floods. There are more extreme dries but also more extreme wets."

Ms Tryhorn's study focused on serious bushfires in the Victorian Alpine shire in January 2003 that were followed by thunderstorms and flash flooding, which claimed the life of a local woman. The fires burnt for two months, after several years of below average rainfall.

Significantly, she found that the bushfire and drought conditions actually increased the risk of flooding.

"The soil is hydrophobic; it is very dry and won't absorb water," Professor Lynch says. "It is also black, so that heats the surface and the surface heats the atmosphere above it and that makes the thunderstorms more intense."

The finding has implications for handling bushfire emergencies, particularly in the Alpine regions, she says.

"We can say that emergency preparedness should include the potential for flash flooding after fires in alpine regions. That's what we are telling the locals. With an enhanced bushfire season there is always the potential for more of these, but given the drought, there simply may not be enough moisture. The effects of fire last for several months, so if the drought breaks there may be a problem."

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