Although floods, or more accurately flash floods occur nowadays in our tiny republic, it is still considered ‘ponding’ in terms of magnitude of flooding as compared to that in other parts of the world. Just earlier this year, the combination of Tropical Cyclone Tasha and La Niña brought heavy rainfall to Queensland, Australia, with many attributing the main culprit of the ensuing floods to La Niña. What happens during La Niña is that the sea surface around the western Pacific (where Australia is situated) reaches record warm temperatures. Warmer oceans produce damper air, thereby leading to more rain. Stronger east to west trade winds that typify La Niña drive the rain clouds onshore, leading to greater rainfall. Even the floods in Singapore were thought to be caused in part by La Niña, in addition to rainfall caused by tropical cyclones and squalls.
In Queensland, continued rainfall occurred over the river catchments, which eventually resulted in rivers breaking their banks and causing widespread flooding. One of the consequences of flooding was that the Brisbane River, which broke its banks, carried along a toxic plume comprised of pesticide and heavy metal-laden sediments. Floodwater that ran over agricultural and industrial areas washed chemicals into the river. According to an estuarine biology expert, Associate Professor Greg Skilleter from the University of Queensland, the storm water run-off from industrial area carried huge amounts of lead, zinc and hydrocarbons. The fear is that this toxic plume could cause enormous damage to the rich marine environment at Moreton Bay where the Brisbane River empties into, and this could take up to two years to recover. Economically, the seafood industry was under threat.
The biggest threat of the floodwater is to human health, so much so that the Australian Medical Association Queensland President Gino Pecoraro urged households to remain careful of the receding floodwaters, which contained potential health hazards like infectious bacteria, poisonous chemicals and ‘traps’ that could cause one to trip and fall.Pecoraro warned the Queensland public:”I’d ask everyone please keep in mind that these waters have passed over farming and industrial areas and could contain toxic chemicals, fertilisers, oil and waste”, and he advised residents involved in the post-floods clean-up to wear appropriate clothing and not take any risks.
Although the magnitude of floods in Singapore is nothing like what is experienced in Queensland, there can be similar potential implications in the event of a flood – floodwaters that passed through industrial areas or parks could carry potentially toxic chemicals which will eventually enter our water system, and on a serious note, pose a threat to the health of those who are exposed. An article dated 4th May this year by AsiaOne reported that heavy rains caused flash floods in Bishan and Ang Mo Kio. Eyewitnesses spotted floods in Nanyang Polytechnic, Ang Mo Kio Avenue 5 and Ang Mo Kio Industrial Park.
Ideally, we would rather prefer our drainage system setup to be adequate enough to drain off the excess rain water. However, in recent times when what many speculate to be the impact of climate change, levels of rainfall could rise. And this year, countries close to the Pacific Ocean such as Philippines and Australia were caught out by a brief La Niña episode. For countries that were affected by floods brought on by La Niña, it will be more prudent to begin planning of the drainage system to pre-empt an abrupt rise in rainfall as a result of such episodes. The last La Niña episodes took place in 1988/1989 and 1999/2000, and such occur in cyclical patterns. Pertaining to climate change, a warmer world not only leads to more intense droughts, but it could also lead to more intense monsoon rains and floods. However, it is still any body’s guess whether climate change could intensify effects of El Nino and La Niña. Regardless of the causes, if floods ever occur, there must be ample preparations for their eventuality to minimise the level of damage.
Such a preparation for the eventuality of a flood will require an integrated approach with our meteorological services, authorities and operators of industrial estates that are likely to experience floods working together. Operators from industrial areas and parks must realise the dangers posed by certain chemicals they may have in their possession either as products, precursors or those used in certain processes and effluents if they leak out in the event of a flood, and enter the waterways or pose health risks to the public. The meteorological service constantly monitors rainfall patterns and should warn of the likelihood of a flood, and the authorities should give impending warning of a flood. Such flood warnings should be issued early to operators of industrial estates, so that they can store such chemicals in a way that makes them unlikely to be exposed to the floodwaters and leak out. Authorities may assist operators with the safe storage of such chemicals in the event of a flood.
Lastly, the onus is also on the general public to ensure that they keep dry and away from floodwaters as much as possible especially if they do not know if such waters contain chemicals, oil or other heavy metals in run offs from industrial estates and other places. If they cannot avoid the floodwaters, it will be best if they can protect their skins with some waterproof materials. Besides chemicals, even something as little as a scratch from a sharp object in the skin can lead to infection from bacteria carried in the water. And it is very easy to suffer a cut if the water is murky and one accidentally steps on a sharp object.