Climate outlook, what does a potential La Nina mean for construction?

You may have seen a number of articles recently about the forecast La Nina, which if it eventuates will be the third consecutive year, which according to BoM has been recorded only three times in the past 70 years. For a La Nina weather event to be officially declared, a number of phenomenas must occur, including below average sea temperatures, a negative IOD (Indian Ocean Dipole) and positive SAM (Southern Annular Mode), which are indications of various wind, ocean and atmosphere readings…

Source: BoM Rainfall Outlook (September to November 2022)

What is more certain is the rainfall outlook for the coming Spring period (September to November) is looking like ‘above average’ rainfall for the eastern half of Australia. In addition the first wet season rains are expected to occur earlier than normal for the majority of Queensland and Northern Territory, with inland areas within eastern Australia also looking at a far wetter than normal Spring. Given the past few years you may be wondering what is ‘above average’ rainfall and what is the probability that such events may occur. The following table presents historical median rainfall totals for the period September to November for a range of locations along with the forecast probability that such median rainfall totals may be exceeded.

Source: BoM Climate Outlook (September to November 2022) http://www.bom.gov.au/climate/outlooks/#/rainfall/median/seasonal/0

If you are involved in construction or development whether it be site based or not, you should start planning ahead as to how you can minimise the risk of a potentially wet spring and even summer. Environmental risks for wet conditions are typically related to management of Erosion and Sediment Control (ESC) during the construction phase and minimising water quality impacts. Project risks will include increased financial pressure, possible reduction to site activities and production which will impact time-frames and added challenges for even basic tasks like moving around the site. There are a number of practical ways in which these risks can be reduced onsite through effective planning, adoption of effective ESC measures and appropriate ESC strategies. We will have to wait and see if the predicted wet weather occurs or not over the coming months, however failing to effectively manage and prepare your site for increased rain is certain to increase the likelihood of problems (environmental, financial and timeframes) you will face. Regardless of the size of the rain event it is not an excuse and your defence to non-compliance cannot be solely based on ‘it was just too much rain to be expected to control onsite’, in other words you must be proactive and prepared!