La Nina is a periodic interaction between the Pacific Ocean and the Earth’s atmosphere, and the annual monsoonal low pressure trough which brings wet weather to the region. La Nina has not only affected Queensland and New South Wales, but it has left a trail of destruction elsewhere: Brazil (more than 270 have died in floods and mudslides) Sri Lanka (32 dead and 900,000 homeless), the Philippines (40 dead and 1.3 million displaced in flooding) Southern Thailand (2 dead and 3000 displaced in flooding), Europe (severe flooding in Koblenz, Cologne and Condron) Northeast USA where blizzards have shutdown airports and Europe mid-December where there was also airport chaos due to heavy snowfalls. In Queensland, the death toll from the December and January floods stands at more than 40, with several people still missing.
The Meteorologists knew that La Nina was on the way as early as April 2010 when she showed off her trademark heavy rains and strong southeast trade winds from April through to the end of 2010. When El Nina arrives the Australian drought is broken.
One of the reasons for the devastating floods this year has been the arrival of La Nina, bringing with her an unusually high amount of rainfall. The higher levels of rainfall from September onwards has meant that the dams in Queensland had reached full capacity, and that the rivers had begun to swell with the flow of water. In the long term this is good for the Murray-Darling basin which had been suffering through the drought caused by El Nino.
The last time that there was a devastating flood was in 1974 when massive flooding in Brisbane killed 14 and 6,000 homes were destroyed or damaged, which was also due to La Nina. Prior to that, in the 1950s the Hunter Valley (Maitland) floods created an inland sea with 25 people being killed. That flood was the subject of a movie called Newsfront.
As a result of the arrival of La Nina there has been an increase in wet and humid conditions. This has led to increased rains in Victoria, as well as other parts of NSW that are not normally affected by La Nina. In late November, early December the rains in NSW and Victoria caused massive flooding. The towns affected included Mudgee, Wagga and Queanbeyan, as well as parts of Victoria. At the present time there are floods in Echuca and Horsham. If we get further heavy rainfalls here in the ACT I would expect that Queanbeyan could face flooding for a second time. The Molonglo river is still very high, and on top of that the lakes around Canberra are at full capacity. The Cotter dam is also at full capacity.
Even though the coming of La Nina explains to some extent the reason why the floods have been so devastating it is not the full story. There are other reasons for the devastating consequences around Ipswich, Toowoomba and Brisbane. It has to be remembered that in a tropical region such as Queensland, that there is only two seasons – wet and dry. The dry normally begins around May-June and lasts until about September when the humidity begins to ramp up again. It is quite normal for flooding in some areas of Queensland during the wet season. It is usually when El Nino is in effect that there is a drop in the normal rains during the wet season, which in turn affects the river systems.
I think that a part of the reason that people were caught off guard and were not ready for the effects of La Nina is that they had believed the big lie of Globull warming. In other words they believed that there would be less, not more, rain and as a result they had begun to do things that had consequences when the big rains came. Yes, La Nina has her influence, but the mistakes that were made by those in authority have also played a big part in why Brisbane was devastatingly flooded and so many people have lost their lives.