Discussion: DISCUSSION Free

by Paul Jowitt (November 2008)

Although I would support Paul Jowitt’s paper in relation to most of the UN millennium goals and the Institution of Civil Engineers’ (ICE) role in promoting the achievement of these goals with other professional institutions and governments worldwide, I must take issue with some of the statements on climate change.

In October last year, I attended the presentation of a paper published in Civil Engineering by David Bellamy and Jack Barrett33 on the effects of increasing carbon-dioxide emissions on surface temperatures. The paper demonstrated that, excluding other effects, a doubling of carbon dioxide from pre-industrialisation levels (285–570 ppmv) would mean a global increase of just 1.5°C. It also showed that predictions of the side-effects are associated with several serious uncertainties and cannot be relied upon to give accurate forecasts of future trends. at the time of the lecture, the chairman at the presentation promised to review the possibility of a proper debate around the conclusions in the paper and to date we have heard nothing.

Until the issues are properly addressed, I cannot support Paul Jowitt’s statements on the necessity to address the issues on climate change, although of course I do support the other issues on reducing dependency on fossil fuels and taking a sustainable approach to civil engineering design and construction.

I would also query Paul Jowitt’s statements on hurricane Katrina being a product of climate change. This was not the worst hurricane in the last 100 years (this was super typhoon Tip in October 1979) but its effect highlighted the appalling state of New Orleans’ flood defences.

As civil engineers, the best we can do with regard to the subject of climate change is to listen to the opinions and study the evidence produced by those that have established competence in the field, recognise the uncertainties, take a judgement on it, and then prepare as civil engineers to do what is necessary.

In a subject as complex and as uncertain as climate change, there will be conflicting views and opinions, so it would be unwise to rely on a selective and narrow range of opinions. I think for ICE to convene a further meeting specifically to debate Bellamy and Barrett’s conclusions that climate change and human activity are unrelated would not be particularly useful. Neither would it command much authority. If people want to discuss climate change and the conflicting issues surrounding it, there are other organisations with a core discipline that is fundamental to that debate. an unbalanced debate by extravagant climatologists and maverick climate-change deniers might be interesting, but could end up as a bit of a circus. I doubt it would sway the minds of many serious climatologists on either side of the argument. I am not sure it would provide a robust basis for the acquisition of serious knowledge by civil engineers either.

On the other hand, if there is to be a debate on what engineers need to do to adapt to climate change and mitigate its effects, then that is something institutions of civil engineers across the world should be playing a proactive role to stimulate. Indeed, ICE clarified the steps it is taking to develop an authoritative and balanced policy on the issue in Civil Engineering34 immediately following the Bellamy and Barrett paper.

With regard to climate change, time will be the judge. I hope the contributor’s judgment is right and mine is wrong, because only then will doing nothing not lead to major social, environmental and economic disaster. In the meantime, as engineers, we had better prepare for the future.

We need to do what we can to adapt our infrastructure to the effects of climate change – irrespective of its causes – which are already locked in to the earth’s climate, and we need to mitigate the impacts of our infrastructure on fuelling the causes of climate change and, where possible, take actions to reverse them.

I made no claim in the paper that hurricane Katrina was some extreme event of unprecedented proportions, though I did say that Katrina’s strength might have been intensified by increased sea temperatures in the Caribbean. That is, the pattern of occurrence of events towards the extremes are being affected by climate change – hurricanes of a certain strength, flood events of a certain size and so on will occur a bit more often than they did. The contributor is absolutely correct to state that Katrina’s impacts were exacerbated by the poor state of New Orleans’ flood defences – in fact, in this section of the paper I was attempting to explain that inadequate and vulnerable infrastructure was a major source of concern, which will only worsen if subject to even more extreme weather patterns.

by John Sreeves (November 2008)

I would query the propounded benefits of the reconstructed Welsh Highland Railway. The adult fare of nearly £20 for travelling the 11 km from Porthmadog to Beddgelert will not encourage people to leave their cars behind and use the railway. Indeed, in these straitened times, they are more likely to bypass the railway entirely and look for a cheaper alternative.

For essential journeys private car transport is usually cheaper than the railway, especially for families. Many passengers will be travelling for the spectacular scenery and unique ambience that the train has to offer as part of a worthwhile holiday experience. The railway offers an environmentally sustainable alternative within the corridor served but, in the opinion of the author, a significant modal transfer is unlikely to occur without one or more political measures – such as restricting car entry/parking places in the snowdonia National Park, increasing parking charges or subsidising fares.

by David Collings (November 2008 special issue)

The reference to both the Cleddau and Yarra bridges states that both bridges collapsed during construction. Unless the design of a bridge is dependent on the method and/or sequence of erection, it is not for the engineer to instruct or order any. In the case of the Yarra collapse, the contractor elected to erect the three-cell deck in two portions, each of different section properties, leading to different stress and deflection regimes in each and then finally trying to marry the two together.

The paper omits to state whether or not the methods of erection of these bridges played a part in their collapses, only to point out that both were designed by the same engineer, Freeman Fox. However, there is no mention of Freeman Fox’s achievement of the Roberts award for innovation, an Institution of Civil Engineers gold medal and the presidency of ICE by three of the firm’s partners called to give evidence to the Royal Commission.

By contrast, the apparent inadequacies of design which caused the excitation problems on the opening of the London Millennium Footbridge were not linked to the highly respected engineer of that bridge.

A few years ago I was in a taxi on my way to the British Construction Industry Awards to receive an award for a major concrete box-girder bridge I had designed – the Bangladesh–UK Friendship Bridge.16 In the taxi were a couple of colleagues and the conversation touched on the collapses of box girder bridges in the 1970s. I was surprised at the vehemence with which one of the party reacted in denouncing Freeman Fox. It transpired that his uncle was one of those killed by the fall of the Yarra Bridge. The family’s loss was still keen after 30 years, highlighting to me the personal tragedies behind the statistics of lives lost. In such circumstances the citations offered by the contributor do not seem relevant.

The main thrust of the contributor’s question is related to the influence of construction methods and sequences. There has been a significant advance in this over the decades since the Yarra and Cleddau failures, modern safety regulations require the designer to consider construction methods, particularly if a variation in that method would lead to different stresses or deflection regimes. The Bangladesh–UK Friendship Bridge is an example of current best practice, with the designer working with the contractor in developing a construction sequence and ensuring stability and structural adequacy at all stages of construction.