Edge of Darkness: damned walls, floods and landslides

Editor’s Note: This is one of a series of articles under the heading ‘Edge of Darkness’ authored by Trevor Berrill (Sustainable Energy Systems Consultant & Educator) and Ian Curr (BSc UQ Grad Dip ATAX). These articles are about systemic failure i.e. to properly manage Queensland’s water, power, and transport systems in an ecologically sustainable way.

“The Somerset and Wivenhoe dams are located at the Junction of the Stanley and Brisbane rivers. The Somerset sits atop of the Wivenhoe. They have separate catchments. The Somerset catchment is the Stanley River and the Brisbane River is the Wivenhoe catchment. The Somerset releases its water into the Wivenhoe which then releases into the Brisbane River”

— “An observation of the confluence of statistical aberrations,
dam ratios, timing and uncommon
rainfall events that combined to have
our leaders draw incorrect conclusions.”
by J. V. Hodgkinson

Wivenhoe dam has so called ‘fuse plugs’ that are a mechanism to prevent the dam wall from failing. This is clear if you stand at the lookout near the dam wall.

These fuse plugs are walls of gravel devised to erode as the dam fills to prevent damage to the dam wall.

If the dam wall breaks, that is failure (at least according to the engineers).

This safety mechanism was introduced as recently as 2004 when it was realised that a rain event (like Dec 2010/Jan-Feb 2011) could overwhelm the dam wall.

It was the unprecedented release of 645,000 megalitres of water through the five spillways on the Tuesday night of 11 Feb 2011 that caused the Brisbane river to rise near to 1974 levels.

I do not agree with the scapegoating of the engineers for the action they took by releasing the water.

They could have released the water earlier but the rain event was such that the dam wall would have been threatened – and if the rain had not stopped on the Wednesday/Thursday there would have been nothing they could do the fuse plugs would have blown and larger amounts of water released.

This is how the system was devised.

It is the system that is at fault, there was not the political will to realise that the building of dams above huge water courses is risky business. Twice in my lifetime lives have been lost because of systemic failure of the Somerset/Wivenhoe dams.

Especially when unrestrained development below means that people are housed on the flood plain.

It is the developers and the politicians that approve such madness that are at fault.

Big Wet brings landslides
It has been known for a long time by experts that Cunningham’s Gap is likely to fail. Landslides often closes the road through the Gap. This is the major arterial road taken by transport trucks to and from Sydney. Trucks coming down the range feed into the new five lane Ipswich motorway. This feeds into the two lane Ipswich road that goes through suburbs like Annerley in the inner city. Major traffic jams result and the quality of life of people who live and work in these suburbs is diminished.

Yet no attempt has been made to fix the problem. There is insufficient political will.

So when the floods hit in December landslides closed the Gap again. All trucks were diverted to Toowoomba which could not cope.

Engineers would be telling the Bligh government that they have to close the Gap for some months to prevent rocks falling on the road through the Gap.

But the government refuses to take more than band-aid measures.

This is because of pressure from retailers, trucking companies, businesses in Brisbane whose profits depend on the road staying open no matter how unsafe it is to the drivers and cars that navigate the roads through the Gap.

One day a landslide may do what the politicians will not, close the Gap permanently.

Ian Curr
17 Feb 2011

[ Ian Curr lived on MV Careel 1972 – 1975 on the St Lucia reach of the Brisbane River. He was on the MV Careel during the 1974 floods.]

See also Edge of darkness: will flooding in Qld cause load shedding at power stations?

Reference:

Experts trying to balance flow almost lost control