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Better Planning for Extreme Floods Possible: A Note from Stewart Franks

DESPITE increased understanding of a number of different climate processes and their impact on a range of different timescales, this knowledge is not being used to inform planning and decision making. This is because long-term climate risk is often viewed only in statistical terms.

For instance, engineering techniques for estimating flood risk, where records exist, are largely based on simple statistics of their historic occurrence rather than on any real understanding of the processes that actually cause them.

In essence, if we have 100 years of flood record, then the largest flood measured represents, more or less, the hundred year flood level. This hundred year flood level is probably the most important of hydrological statistics in terms of its use in planning management. It is the yardstick by which decisions are made.

The problem with a simple statistical representation of risk is that it implies a static climate – the expected flood risk is equally likely in any year, irrespective of the actual climate processes that may or may not be dominating at that particular time. If this were the case, we would expect to see an equal spread of floods throughout our historical records. In Australia and in fact many other parts of the world, this is not so.

The observed history of Australian flood risk demonstrates that this fundamental assumption is invalid – climate is not static – Australia regularly experiences epochs lasting between 20 to 40 years where extreme floods cluster only to then be succeeded by a similarly long period where droughts dominate and extreme floods are rare occurrences.

In Australia, between 1910 and 1945, long-term and persistent drought dominated the Australian climate – very few floods were experienced – this was largely due to the dominance of El Nino events.

Around 1945, we experienced a major change in climate from this previously El Nino dominated regime to one dominated by La Nina events. This led to as much as a three-fold rise in the average annual maximum flood. The dominance of La Nina and associated southward shift in the location of the Inter-Tropical Convergence Zone meant that rainfall was frequent, and frequently extreme.

Around 1975 we had another major climate shift – a marked change in the Pacific that is associated with a return to El Nino event dominance. Once again, Australia suffered repeated droughts and again very few floods.

Since 2001, we’ve had seven years of drought, initiated and then sustained by El Nino conditions, but more recently, the last couple of years have seen a shift towards marked La Nina activity.

Last summer was a classified La Nina event, whilst this summer we saw a late rush of La Nina activity. Consequently we’ve seen an 18-month period of disastrous storms and floods, including the recent widespread flooding.

This recent La Nina activity has not broken the long-term drought everywhere but has been useful in many places where the impacts of ENSO are strong and largely reliable – typically those with summer dominated rainfall regimes – but also with typically devastating consequences.

The double-edged regional impact of La Nina aside, the recent La Nina activity has not made much of an impression in other parts of Australia, notably Victoria and South Australia. Indeed, the recent tragic bushfires are most likely due in large part to the ongoing impact of the unrelenting drought.

Long-term drought in these regions was the primary cause of the initial high bushfire risk leading to the dreadful bushfires – low rainfall means dry combustible fuel. Soil moisture feedbacks mean that when soil moisture is low, the air temperature is hotter, the humidity is lower and the air column itself is more unstable. These conditions are all amenable to increasing extreme bushfire risk.

And so we find ourselves witnessing the iconic extremes of fire and flood devastating different regions of Australia simultaneously. Dorothea would have wept – she might have seen it before us but we are seeing it worse.

Many might even be tempted to say that the current perverse circumstance of deadly bushfires in one part of Australia and widespread flooding in others is a further sign of CO2-driven climate change.

However, an alternative understanding would be that whilst southern states continue to be in drought with the attendant bushfire risk, other regions of Australia may have started to experience a natural change in climate that would be more consistent with their historical instrumental evidence of flood and drought risk, despite increasing atmospheric CO2 concentrations.

The historical record of climate variability suggests that we should expect a return to a 20-40 year period where La Nina dominates the climate of at least eastern Australia once more. The observation that many regions of Australia routinely experience multi-decadal variability of flood and drought, suggest that we should expect a return to major widespread flooding on a regular inter-annual basis, and for entirely natural reasons.

There are other known climate mechanisms relevant to Australia that also display marked multi-decadal variability that only add to the difficulty of climate prediction in different parts of Australia. It is however increasingly recognised that different observed and studied climate modes appear to have definable interactions.

Further studies of the interactions between climate modes may yield additional insights into the possibilities and limitations of prediction and estimation of risk, both now and into the future. They might also inform us on the true relevance of atmospheric CO2 concentrations in a naturally varying climate.

And yet at present Australia’s historic variability does not figure in typical estimates of climate risk for planning purposes. Nor though should we pay much heed to those that may loosely call themselves climate change scientists and who make alarmist claims for the future climte. They should acknowledge that we never could predict the future climate of 10, 20, 50 or 100 years time, at least not with any credibility. It is no different now that we fear CO2.

If we cannot prevent climate-related disasters we can at least prepare for them. The recent tragedies of both fire and flood have lessons to teach. We should engage ourselves in developing more effective measures to reduce our vulnerability to the extreme vagaries of climate variability. More prescribed burns and more flood infrastructure would seem appropriate.

Whether we can predict climate on multiple timescales usefully or not, we should certainly be preparing ourselves for both ends of the spectrum of climate extremes at all times. I would argue that in a country as vulnerable as Australia, this should be happening irrespective of any consideration of possible impacts of increased CO2.

After all, if we fail to cope with natural climate variability what hope have we for coping with any supposedly catastrophic human-induced climate change?

********************

Stewart Franks is an Associate Professor at Newcastle University.

The text is republished from ABC Unleashed with permission from the author.

Margaret Menzel provided the photograph of the drown cattle taken at Cowan, North Queensland, in February 2009.

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22 Responses to “Better Planning for Extreme Floods Possible: A Note from Stewart Franks”

  1. Comment from: bazza


    Stuart Franks follows on some well known historical observations of bunchy ENSO activity over decadal time scales by fearlessly predicting parts of Australia ( not southern) “may have started to experience a natural change in climate”. Then he wants climate change scientists to “acknowledge that we never could predict the future climate of 10, 20, 50 or 100 years time, at least not with any credibility”. Whats good for the goose……….But maybe he has it back to front. Climate scientists, despite a decade of trying, have been hampered in predicting decadal patterns for want of a mechanism – not so for climate change scenarios.

  2. Comment from: janama


    meanwhile all that water is flowing into lake Eyre. The water will then evaporate and could possibly relieve the southern drought.

    I do hope the scientists are out there measuring it for future reference.

  3. Comment from: Ian Mott


    As far as realistic planning for extreme flood events goes, nothing beats a good Dam.

    On the Herbert River above “little venice”, a.k.a. Ingham Qld, there appears to be only one dam that made it into google earth, a modest 260 megalitre one at the very top of the catchment.

    So not only was all that water in the recent floods completely wasted, it all flowed out onto the Great Barrier Reef where it kills coral. And no, it is not the sediment load that kills the coral. It is the fresh water itself that does the damage.

    Yes, we need flood events to maintain breeding rates of estuarine species. But in this instance that seasonal flush was delivered on day one of the floods. The following three weeks flow was all wasted water.

    And thanks to the ALP’s “wild rivers” legislation, which seeks to outlaw any sort of agricultural development in the Gulf catchments, the past 8 weeks of flows in those catchments have also been wasted. And will continue to be wasted for as long as these bogans remain in power.

    Dams on all these rivers are justified on damage minimisation grounds alone. That does not mean that all water must be captured. But it does mean that there are numerous “fiscal stimulus” projects out there that will actually produce long term economic benefits.

    But what do we get instead? Sleazy, grande mall, vote buying that maintains all the economic froth that has contributed to our current economic problems.

  4. Comment from: Luke


    Of course realistic planning for extreme bulldust nothing beats a quick shower.

    Strange that floodplains flood. Why is it so? Wonder what happens if you build communities on them. Do you eventually get flooded?

    Is the water in the Burdekin and Ord Dams all used – nope but lets build some more dams just in case.

    And all that agriculture that would benefit from these new dams would be dumping photosystem II herbicides onto the reef would have to be good for it wouldn’t it? (along with the 10x pre-European sediment and heaps of N and P). Anyway diuron in your prawns improves the flavour and makes you less aggressive.

    All the heavy metals now washing around from the excellent mining practices will probably make your gonads shrivel. http://www.abc.net.au/news/stories/2009/02/27/2503412.htm

  5. Comment from: Ian Mott


    Didn’t I read somewhere recently that the main pollutant on the reef was coffee?

    Standard departmental defensive statement from boy wonder. How would a Dam on a gulf river deliver herbicides to the reef, moron? They are on the other side of Cape Yorke Penn.

    And what f@#$g diuron? Cane farmers don’t use it during the wet season and it breaks down. The only research on the so-called problem was conspicuously short of specifics and long on ignorant speculation.

    And funny how the claimed 10x increase in sediments can only be found at specific sites (offshore from Townsville) where the boundary of deposition has been shifted, most likely due to increased urban runoff pushing the sediment stream a bit further out to sea to Pandora Reef. That is, 10x increase on a few carefully selected sites and jack $hit change everywhere else.

    What a shonk you are. And eager to find any pretext to do absolutely nothing to help anyone but your own tribe of eco-perverts. Meanwhile excess fresh water doesn’t just show up as a sediment blip on the coral cores, it kills the damned coral outright.

  6. Comment from: Luke


    Hahahahaha – about what you’d expect from an industry apologist and denialist

    Herbert flows into the Gulf does it.

    Obviously the Gulf systems flowing into the Gulf go straight to a significant prawn hatchery.

    “Off Townsville” – well matey – could it be that’s nearby where the second biggest reef catchment discharges – you know – that Burdekin River thing that exits between Home Hill and Ayr. Don’t try and bullshit you way out of the obvious. Urban runoff my bum ! You’d have to be on Nimbin Gold to try that on. Yes it’s a pity the pre-dam flood correlations are such a good match in the records with the Burdekin flows. It’s also a pity the recent water monitoring nails it too !

    Let’s see …

    http://www.gbrmpa.gov.au/__data/assets/pdf_file/0005/21893/part2_mmp_annual_report_overview.pdf

    Diuron and atrazine products – all there…

    and more in

    2007 Water Quality Report
    Great Barrier Reef catchments and inshore ecosystems
    ISBN 978-0-9803613-3-9

    Anyway here’s thoughts to balance your proposed madcap development spree

    http://www.epa.qld.gov.au/publications/p02740aa.pdf/Review_of_the_Fitzroy_River_Water_Quality_Issues_/_prepared_by_Professor_Barry_Hart_for_the_Queensland_Premier.pdf

  7. Comment from: Ian Mott


    Nice try at a sidestep, boy wonder, but it won’t work. Clearly the words “Herbert River above .. Ingham” would demonstrate that I am aware that the Herbert does not drain into the Gulf.

    And you still don’t get it. The Burdekin catchment has been subject to clearing (The upper Burdekin is still 76% woody vegetation) which will have increased catchment water yield and increased the volume of outflows north of the river mouth. The satellite photos clearly indicate the extent of the plume as it heads north along the coast past Townsville. It does not reach as far an Hinchinbrook as this area is still described as “pristine”. Pandora reef is quite clearly at the end of this plume and it follows that if there has been a structural increase in catchment runoff then the plume will reach Pandora more often and resulting coral cores will register those more frequent visits by the plume as an increase in sediment loads.

    In addition, the volume of water from the change in water yield from the increase in urbanisation of Townsville is more than sufficient to nudge the plume a bit further out to sea where it increasingly intersects with Pandora. Capture that urban runoff and the plume will shift back closer to the coast and show up in the cores as a decline in sediment load.

    The point is that the official science is guilty of blatant cherry picking. Focussing on the few parts of the reef where a change is detectable. The samples closer to the river mouth, and those further away, will not show anywhere near the same variance. Pandora Reef is not representative of the GBR and you know it.

  8. Comment from: Luke


    Talk about side-stepping – you’ve dumped herbicides knowing you’ve been caught out.

    Tree clearing is mostly irrelevant – it’s overgrazing aka flogging. High grazing potential runoff is about 40-50% of rainfall vis a vis 10% in exclosures. Generally there is a 2 fold increase in infiltration rate for a 10-15 % decrease in surface soil bulk density

    So I’m very happy for you to suggest runoff discharge and sediment is getting worse and travelling further. THATS’ THE POINT !

    Lough 2007 http://www.agu.org/pubs/crossref/2007/2006PA001377.shtml shows research from up to 25 coral cores from 15 nearshore reefs regularly influenced by river flood plumes. Separate reconstructions are developed for four rivers (Herbert, Burdekin, Pioneer, and Fitzroy), and these are used to reconstruct total annual freshwater flow into the Great Barrier Reef.

    Although there appears to be no overall trend toward wetter or drier conditions, the reconstructions suggest that the variability of rainfall and river flow has increased during the twentieth century with more very wet and very dry extremes than in earlier centuries ….

    I’m also happy to move the discussion to Keppel Bay if you’d like to talk how disproportionate amounts of the Western Nogoa and cropping Tertiary Basalts end up in the Bay. More land use impacts.

    There is no cherry picking as all the reef catchments are different. The simple point is that European land use has significantly changed terrestrial runoff and export of sediment, nutrients and herbicides. Climate change may be assisting.

    The real guilt is for you to continue in denial when even industry has moved on to improving land management practices.

  9. Comment from: janama


    Shark expert Ben Cropp said yesterday the outer reef was more or less the same as when he started diving 50 years ago, although more accessible corals had been damaged. Patrick Ligthart, a volunteer with the Low Isles Preservation Society, said his section of the reef had never looked better, and he was sceptical about predictions of its demise.

    Mr Cropp has had experience of being ostracised when he opposed the popular view in the 1980s that the reef would disappear because of the crown of thorns starfish.

    “The only change I’ve seen has been the result of over-fishing, pollution, too many tourists or people dropping anchors on the reef,” he said.

    http://www.theaustralian.news.com.au/story/0,25197,24811996-11949,00.html

    Ben Cropp doesn’t rely on grant money to survive.

  10. Comment from: cohenite


    Good post on the chain-saws Ian. The salient point about Stewart’s article is that reasonable climate prediction in a guise of flood mitigation and insurance risk calculation has to be based on real climate patterns not GCM conjecture on the basis of a failed theory; the notion of the 100 year drought is just another fallacious example of that conjecture.

  11. Comment from: Luke


    Cohenite just keep squeezin them lil’ hands so clenched in church and say it again and again. It will make it so. – the point is that the IPO is UNPREDICTABLE …. hahahahaha

    The salient point as always is that Franks ignores 50% of the story. zzzzzzzzz

  12. Comment from: cohenite


    luke; IPO is regular enough to be used as the dominant climate determinant for a host of other climate indices;

    http://www.hydrol-earth-syst-sci.net/11/1295/2007/hess-11-1295-2007.pdf

  13. Comment from: Luke


    In retrospect. …. yawn

  14. Comment from: Luke


    So Cohers – if it’s the dominant component – why does the IPO only come out as EOF 2 when you look at either SST or NMAT since 19th century.

  15. Comment from: cohenite


    luke; I don’t know what paper you are referring to but the McNeil and Cox piece I linked to attributes a good correlation between IPO and SPCZ and ITCZ and concludes that stream indices are most likely the result of natural climate variation.

  16. Comment from: Luke


    I’m referring to Hadley Centre work which says EOF 1 of the SST data is the centennial trend, EOF 2 IPO and EOF 3 (only a tad behind EOF 2) is the AMO. Biggest driver off SSTs from two independent data sets is the centennial trend not the IPO. I offered to share but you didn’t contact moi.

    Don’t have any major issues with McNeil & Cox. Although Lough 2007 would show you much greater variation this century. (wet and dry)

  17. Comment from: Ian Mott


    Still wrong, Luke. The sediment changes are not major impacts on the whole reef. All you have are some carefully selected, unrepresentative sites that have undergone detectable change due to their specific location.

    So lets just walk you through this nice and slowly, so even ministerial advisors can comprehend it. A doubling of sediment load at 1.5% of the reef merely produces a 1.5% increase in reef sedimentation. Otherwise known as 1 tenth of two fifths of sweet FA.

    There goes that old extrapolation to absurd extremes again, Lukaldinho. Standard MO for the shonkademics. Just another day in “Frankenscience”.

    Thanks Cohenite. Keep a dancin there.

  18. Comment from: Luke


    Utter drivel Motty. Face it – your own mob have stopped listening – you’re marginalised from the debate through being too silly for words. Standard MO for non-activists Cohenite. More sediment than ever. Kilotons of it. Going further than ever before.

    So get the logic Cohenite – take a picture of filthy leaky sewer pipe – Motty complains it’s not actually leaking as the picture is biased through being next to the leak. hahahahahahaha – classic!!

    Nobody said it was the entire reef did they mate? Standard industry apologist technique is to first misrepresent the entire debate and then argue from that point.

    Although this picture from the flogged Normanby catchment says a lot eh? Another flogged out catchment full of yaks.

    http://www.csiro.au/news/ps2t8.html
    http://www.scienceimage.csiro.au/mediarelease/mr07-sediment.html

  19. Comment from: Ian Mott


    Standard CSIRO frankinscience, Luke. A picture tells a thousand words, most of them bull$hit. So how deep are the plumes and how long did they last before being dispersed by oceanic forces? And what proportion of total sediment ends up on sandy sea bed and seagrass beds which actually appreciate a bit of fertilisation?

    You do accept that there are vast areas of sand between coral outcrops, don’t you?
    And you do accept that most coral structures are not overly condusive to retaining sediment, don’t you?

    The fact that something can be detected by satellite at a particular time does not mean it is an enduring threat to anything. As regrowth clearing confirms.

    And if you really want to reduce sediment loads then get some funding to pave rural roads. They produce 100x more sediment/m2 than a clear fall timber harvest.

  20. Comment from: Rick Beikoff


    Luke,

    You are a very rude man and have demostrated that your personality is not suited to reasoned debate.

  21. Comment from: Jennifer Marohasy » Time to Reject AGW – And Bob Brown


    [...] Better Planning for Extreme Floods Possible: A Note from Stewart Franks February 27th, 2009 http://jennifermarohasy.com/blog/2009/02/better-planning-for-extreme-floods-possible/ [...]

  22. Comment from: Climate Change by Bob Carter « Taylor News


    [...] Despite strident claims by global warming pressure groups, no scientific evidence exists that human carbon dioxide emissions have anything to do with our current climatic woes. Rather, the weather events that are causing us so much present grief represent instabilities related to both short term (ENSO) and longer term (Pacific Decadal Oscillation – PDO) climatic oscillations. That such events would occur is not only predictable in principle, but (in the Australian case) was actually predicted in February 2009 by Dr. Stewart Franks from Newcastle University, who wrote: [...]