The false security of the Wivenhoe safety blanket

A break in normal transmission to make a comment on the floods that will, in coming days, rip through nearby Brisbane and devastate large swathes of South East Queensland.

The Brisbane River in 1974, looking towards the modern day South Bank (home of Expo 88)

It’s only been today that the true extent of the peril has been revealed, that Australia’s third largest city, home to more than two million people, faces flooding larger than the oft-talked about 1974 Brisbane floods.

In late-January 1974 a cyclone dumped massive amounts of rainfall into the catchment for the Brisbane and Bremer Rivers causing devastating flooding in Queensland’s capital.  It was a catastrophic event and precipitated the building of Wivenhoe Dam, an exercise in flood mitigation and water supply for a burgeoning metropolis.  Supposedly Wivenhoe would “flood-proof” Brisbane.

Watching the news reports of the unfolding drama a common theme has emerged of shock and consternation as Wivenhoe reached 200% capacity (100% being it’s capacity for water supply and a second 100% being a flood mitigation “shock absorber”).  For the best part of 30 years the sturdy 2 kilometre barricade of Wivenhoe spillway across the upper reaches of the Brisbane River has been a mental safety blanket for the population of Brisbane.

Incoming! The Brisbane CBD trembles ahead of the 2011 flood peak. (All pics from Courier Mail)

My comment is that there’s a false economy about blindly putting trust into the creation (and spin-doctoring) of man.  While Wivenhoe has prevented minor floods over the years, and will help to slightly minimise what will become known as the 2011 Brisbane Flood disaster, it is about to be shown as completely inadequate in the face of a full-blown blast of Mother Nature’s fury.

History will show that thirty years of politician bluster on Wivenhoe has created a false sense of security which has flowed into poor-decision making.

As recently as two days ago the Brisbane Lord Mayor, Campbell Newman, was trumpeting the merits of Wivenhoe.  For a long time people have gone about their lives, buildings have been approved, developments undertaken, all in the “sure” knowledge that the 1974 floods could surely not happen again.  Over the next 48 hours this fallacy will be revealed to the world in gory and excruciating detail.

Flood rescue in 1974

History is an important teacher.  In 1893, at a place not far from where I currently live, 938mm of rain (38 inches on the old scale) fell in one day.  In the four days leading up to the 1974 floods the catchment of the Brisbane River saw falls of around 500mm in total.  It was enough to drown large swathes of land downstream.  Wivenhoe may have been able to cope with what happened in 1974 again, but it certainly wouldn’t have been adequate in 1893!

In recent months Wivenhoe filled to 100% and at regular intervals the sluice gates have been opened to keep it there anytime it rained upstream.  It didn’t appear as though the dam managers shared the politicians’ confidence in the impervious wall of Wivenhoe – that they were keeping the dam at 100% because they could see the ground was getting soggy and every inch of its flood mitigation capacity might be required if a major rain event did move in.

Flood waters rise upstream from Brisbane

Which it now has.  On Sunday parts of the catchment received 320mm, yesterday falls of 200-300mm were widespread across the catchment (including the bombshell that broke over Toowoomba) and today a solid line of storms have sat over the catchment all day (I’ve been watching the radar) dumping another 300mm or so.  Not quite the 938mm in a day seen in 1893, but close to it over three days and significantly more than was seen in 1974.

The scary thing for South East Queensland is that the wet season is only in its infancy.  It could get a lot worse yet.  And all of the schemes of men will be laid bare if it doesn’t stop raining.

Postscript:  Seems my suggestion the lessons and concerns of history have been ignored is not far off the mark.  Todays Australian newspaper suggests a report on the Brisbane River risks was covered up.

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8 Responses to The false security of the Wivenhoe safety blanket

  1. Pingback: Tweets that mention The false security of the Wivenhoe safety blanket « Co-mission -- Topsy.com

  2. jess says:

    you can bag wivenhoe all you want but the fact is that the 74′ floods occurred without the safety of wivenhoe, we have twice as much rain as caused th 74′ floods and the reason we are not yet in undated is he fact that the wivehoe is there. you cannot possibly blame this on a safety measure that is undoubtedly protecting us from more harm

  3. MUM SAYS says:

    Interesting. So were the comments of my Dentist this afternoon, he says that if you Google you will find that this happens every 37 years since records have been kept….I think he said that even Darwin Cyclone was the same…37 years?
    Ah well, man proposes and God disposes. We must pray that the “missing persons” are found alive….

  4. Finophile says:

    couldn’t agree more.

    Looking through your few comments I see evidence of the same hear up their arse ignorance based stuff that helps propaganda to perpetuate.

    History may be an important teacher but the class is playing games, looking in mirrors and generally being bogans.

    I have made similar observations on the “inland tsunami” just yesterday.

    http://cjeastwd.blogspot.com/2011/01/big-wet-continues.html

    glad to see others are out there who can actually see more than what’s on channel 9

  5. Pingback: It’s alright? « Co-mission

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