Last night a column of smoke rose from Mullumbimby at an alarming rate and several people called 000 – the recent fires on the Far North Coast causing loss of life and livelihood, have left people a bit jumpy – and rightfully so.
The plume of smoke was caused by a cane fire – the fire had a permit and the farmer was doing the right thing, but how do you know when it’s an emergency?
Inspector Angela Daly from the Byron Local Government Area – Far North Coast branch of the Rural Fire Service, said there were calls from Billnudgel to Myocum. ‘The fire was near King’s Creek at Mullumbimby and I sent out appliances from the Mullum and Billinudgel brigades to take a look,’ she said. ‘Everything was in order – farmers are usually pretty good and burn off late in the day and early evening.
‘In this case and in most cane fires, there was a big puff smoke which disappeared really quickly.’
Inspector Daly said that fire permits have been suspended for several weeks, but certain folk can light fires. ‘The Far North Coast Bushfires Risk Management Committee met quite a few weeks ago,’ she said. ‘They decided to suspend fire permits for this year. This means that no-one can light a fire but there are exemptions for essential agricultural activities, such as burning sugar cane.’
The Keetch-Byram drought index
Ms Daly said the problem is people lighting fires when they shouldn’t – the mistake often made is thinking when there are a few mils of rain, things are wet enough to light fires. ‘It’s more about the soil,’ she said. ‘Through the Bureau of Meteorology (BoM), we have access to the Keetch-Byram drought index and this lets us know how dry things actually are then we make decisions about permits based on that.’
Wikipedia tells us that the Keetch–Byram drought index (KBDI), was created by John Keetch and George Byram in 1968 for the United States Department of Agriculture’s Forest Service. It is a measure of drought conditions and is commonly used for the purpose of predicting the likelihood and severity of wildfire.
The index calculates rainfall and air temperature among other factors. The KBDI is an estimate of the soil moisture deficit, which is the amount of water necessary to bring the soil moisture to its full capacity.
A high soil moisture deficit means there is little water available for evaporation or plant transpiration This occurs in conditions of extended drought and has significant effects on fire behaviour.
In Australia it is expressed from 0 to 200, referring to millimetres.
We need a lot of rain to make it safe
Ms Daly says that often people make the mistake when we have a downpour that delivers 20, 50 or even 100 mils of water. ‘Just because we’ve had some rain it doesn’t mean the fire danger is gone,’ she said. ‘As an example today’s Keetch–Byram drought index tells us that today Ballina is 168, Murwillumbah is 165 and Cape Byron is 127. When the scale only goes to 200, those figures are a pretty scary indication of the current fire danger situation.
‘In laymen’s terms on a scale from 0-200 (0 = completely saturated soil, 200 = Associated with severe drought and extreme fire behaviour) it effectively means anything over 100 is extreme. If you are sitting on 100 you need a 100 mils to bring soil back saturation.
‘That means we’d need 168 (Ballina), 165 (Murwillumbah) and 127 mils (Cape Byron) of rain to saturate the soil in those areas and therefore make them safe, or at least safer.’
Ms Daly says that the BoM monitor this all the time. ’It’s just another one of the things they do.’
But the best way to keep an eye on conditions is to look at the RFS website. ‘The Fire Danger Ratings on the website look at the drought factor, windspeed and direction and from that, they produce the fire danger rating, an indication of how a fire will burn,’ she said. ‘It’s really important to remember that right now if you want to light a fire you need a permit.’
You can find the Fire Danger Ratings and the Fires Near Me pages on the RFS website at: rtfs.nsw.gov.au.