The local mayor and councillors, MPs and neighbouring councillors all fronted up to a packed hall of 300 people, but there were two noticeable absences. Despite promising to come, no-one from Melbourne Water, which is responsible for the drainage system across Melbourne, actually turned up. And the state government, which is ultimately responsible for planning, did not send a representative despite numerous requests, including on the floor of parliament.
Whilst much of the meeting was about community and local government responses, I was asked to specifically address what was the elephant in the room: the climate change aspects of the issue. Of course there are reasons why residents don't want to know the problem is going to get worse, but planning and actions can only sensibly proceed with an honest assessment of the problem, both now and it the future. In that sense, the ambivalences at the forum about wanting to understand how climate change will affect coastal communities reflect what is happening right around Australia's coast.
Here's the text of my remarks.
Many factors contribute to the Elwood flood problem. Poor planning in the 19th century means part of Elwood is built on a swamp, and natural drainage is now a concrete canal. Over-development in the catchment in Glen Eira has reduced the capacity of the earth to absorb downpours.
But I have been asked to speak about what will become the predominant influence on inundation and liveability in Elwood, and that is climate change.
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| The map above was drawn in 1886. It shows the ''Elwood Swap'', an area where water from the Elster Creek drained before entering Port Phillip Bay. The red lines show what are now Dickens Street (at the top), Mitford Street (on the right), Glenhuntly Road (at the bottom), and Marine Parade (on the left). In 1888 construction of the Elwood Canal began. It was dug down the centre of the swamp (below). Once the canal was completed the swamp was drained into the canal. Sales of land occupied by the former swap began in 1908, with the final lots being sold in the 1920s. Maps and captions courtesy: http://www.live.org.au/elwood/elwood-1886-a-2012 |
As our climate gets hotter, extreme events will become more common: heat waves, heavier rain, more intense bushfires and severe droughts, extreme melting at the poles.
In the last decade, we have seen an avalanche of extreme events: scientists attribute global warming to making more severe the 2003 summer heatwave which killed 50,000 mainly elderly people in France, the Russian fires in 2010 and the Texas drought, just to name three.
In Australia recently we have witnessed off-the-scale fires in Victoria, the wettest two years on record, record heat waves in Perth this year, extreme flooding events for two summers, and Cyclone Yasi. Last month Mt Buffalo received 525 millimetres of rain in a week. Imagine if that have been 200 kilometres further south, over Elwood!
Extreme events are at the boundary of what is possible with the climate. As the climate changes, those boundaries change. Climate change will be experienced as an escalating series of extreme climate events, until the extreme becomes the new norm.
With global warming, both the atmosphere and the oceans increase in temperature. Warmer air holds more water vapour (7 per cent more for each one-degree Celsius rise), and hence overall more rain and the likelihood of more intense storms, though the patterns will change.
Rising sea temperature drive more intense storms and higher wind speeds. Over the last two years, the Surface Sea Temperature around northern Australia has been at a record high, just as we have record rains and records floods across north and eastern Australia. Tropical rains are being pushed further south over the summer period.
So how will this affect Elwood?
- More intense rain events. As Prof David Karoly of UniMelb says: “Australia has been known for more than a hundred years as a land of droughts and flooding rains, but what climate change means is Australia becomes a land of more droughts and worse flooding rains.’’
A study for Melbourne Water a year ago found that Melbourne should expect more suburbs to be flooded more frequently, that Melbourne's drainage infrastructure will be overwhelmed almost twice as often by 2030, and the area affected by flooding may be 25 per cent larger across most parts of metropolitan area. So the problem is not just Elwood.
The problem is that flood experts say that past events can no longer be regarded as a reliable base for planning for future floods but, to quote Dr Seth Westra: “the identification of an alternative framework for flood estimation remains elusive”. - Higher wind speeds lead to the possibility of bigger storm surges, especially when combined with big tides. Already the modelling for this area, for example as done for the City of Port Phillip, includes 1-in-a-100 year storm surges of one-and-a-half metres, based on a 10 per cent increase in maximum wind speed.
- As the poles melt and seas expand, sea levels rise, currently around 3mm a year, but this will increase. When combined with high tides and strong on shore winds/storm surges, this will at first manifest as inundation "events”.
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| This map done by consultants for a City of Port Port Phillip report in 2007 shows modelling for the Elwood area of sea-level rises and storm surges. The largest blue area (deep blue line) shows a potential storm surge event for an 80cm sea-level rise scenario and 10% increased windspeed on a 1994 event (total for sea-level rise and storm surge is 2.31m) |
The federal government standard says a maximum of just over a metre (1.1 metres), but the most up-to-date science says sea levels rises this century could be up to 2 metres.
Up to 2 metres is what the science says, and you can’t plan on the hope that the worst possibilities won’t happen.
So how did 2 metres become 1.1 metres? The federal government’s 2009 report on “Climate Change Risks to Australia’s Coast” says that “Recent research… projected sea-level rise from 0.75 to 1.90 metres relative to 1990, with 1.1–1.2 metres the midrange”. Climate Minister Wong then told ABC Insiders that “1.1-metre ….is about the upper end of the risk”, and in June last year Minister Combet told ABC News that “The sea level rise of up to 1.1 metre…. is at the high end of the scenarios”.
So what should have been a 2-metre standard got whittled down to just 1.1 metre. In places like Singapore and London, planning is now based on sea level rises this century of 2 metres or more.
And in areas like Elwood, there is significantly reduced drainage capacity with even small sea-level rises. Recent modelling for the City of Port Phillip has shown that a 10-15cm sea level rise is equivalent to a 30 per cent reduction in drainage effectiveness in some parts of the city. And the bigger picture is that the City of Port Phillip has over 9000 addresses within three kilometres of the coastline, and below four metres in elevation.
Two issues stand out as important for local residents:
- Residents need to be fully informed, they deserve the best that can be offered, and they must actively participate in planning their future in Elwood and around the Bay.
- Planning and risk assessments must be based on the most up-to-date knowledge, including on sea levels. There is no point wasting millions of dollars on studies and plans that underestimate the problem, which is what I fear is happening.
David Spratt
26 March 2012
