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Letters 5 March 2009

The Main point: The Severn Barrage will help not hinder the local wildlife

We learn from Robert Benaim (NCE 12 February)) of the necessity to avoid “hysteria” in debating tidal energy. The reality is that the subtidal mud patches in the Severn are barren, as is the water body.

Intertidal sandbanks, most notably the largest, Middle Ground, are barren or verging on barrenness, as are subtidal sand, gravel and sea bed rock exposures.

In the mid-1980’s the British Trust for Ornithology showed that Severn foreshores had the lowest carrying capacity for shorebirds of any in the UK. Since then they have collapsed further.

What is new since the last study phase (1987-90) is that we now have several enormous unbroken ecological time-series, for example shorebirds, almost 40 years, and sea water temperatures, more than 30 years. These confirm collapse of shorebird numbers, which we explain by impact of climate change.

The climate-induced rise in sea water temperature has now reached within 1 degree C of permanently excluding the cold water species, salmon. The rise seems inexorable and is what a barrage is designed to offset.

I mustn’t be hysterical, but it is fair to state that the academic community is “profoundly unsettled” by this rapid ecosystem collapse, which mirrors effects onshore to native trees, butterflies, terrestrial birds, bees etc.

Building a Carfiff-Weston barrage would undoubtedly be accompanied by a massive rise in floral and faunal abundance and biodiversity, as long forecast and as is well documented at the Rance and Annapolis Royal tidal power barrages.

Dr Robert Kirby,

I refer to the letter by Mr Benaim and specifically wish to take up his point that ‘destruction of the Severn Estuary habitat would be of real significance on a local and global scale’.

My research centre has been studying the Severn Estuary for over 10 years. The estuary is an extremely harsh environment, with the very strong currents producing very high levels of turbidity from the outer estuary to well upstream of the old Severn Bridge. 

Our verified computer models show that a barrage would reduce the currents significantly in the region and, in particular, reduce the suspended sediment levels from over 1200mg/l to below 200mg/l. The water column will: become much clearer, have much more light penetration, have increased dissolved oxygen levels, decay and biological activity and, in short, provide a much more productive, but different eco-system.

The loss of intertidal habitat area will only be about 50% of the total and the birds tend to feed on the outer, largely unaffected areas, anyway.  Furthermore, there are already significant changes occurring with regard to bird populations in the estuary; RSPB’s own figures have shown that the Dunlin population declined by 50% to 23,312 between about 1990 and 2000 – nothing to do with the barrage.

My concern is that too many of us within our Institution are not asking for the evidence to substantiate the claims made by various NGOs – not all – that a Severn Barrage will have a devastating environmental impact on the Severn Estuary.

Professor Roger Falconer, Cardiff University, Queen’s Buildings, The Parade, Cardiff CF24 3AA

Falling timber

Simon Smith, Ramboll Whitbybird design director, states that our graduates are coming out of University and they don’t know how to design timber (NCE last week). I would suggest his comment reflects more a lack of demand for such expertise by the consulting engineering profession and the Institutions than a failing by Universities to provide for it within courses.

I have been associated with the establishment of undergraduate and post graduate timber design courses at Edinburgh Napier University for the past 4 years, and the constant disappointment has been the lack of interest shown by UK students in learning how to design using timber.

The courses are based solely on the use of Eurocode 5 and generally I have had only a very small number of UK undergraduate students per annum, and this is in a University where there are nearly one hundred students graduating in civil engineering every year.

What is also disappointing is that despite offering the UK’s only undergraduate and MSc courses in timber engineering as well as CPD programmes in the understanding and application of this Eurocode, there has been no demand from the professions.

As my consulting engineering colleagues should be aware, with the introduction of Eurocode 5 there will be a major change in the way timber must be designed in this country.

The sooner the professions wake up to this and encourage undergraduates and practicing engineers to gain an understanding of the methodology and application of the design rules in the new code, the quicker properly trained UK engineers will be available to assist Simon and others to exploit the growth potential of timber construction.

Jack Porteous (F), St Andrews, Scotland,

Legless lego

Your enthusiasistic editorial about the growth in Lego sales being a key to the future of UK civil engineering may be over optimistic (NCE last week).

My experience (with three sons aged 7-11) is that while Lego may be very popular, it is the Star Wars and before that, Harry Potter sets that get bought, but once built they sit gathering dust on shelves.

Despite my encouragement, the design and creative skills that you refer to are never utilised, as few every get dismantled and built into anything else. I am afraid that all that is being learnt is the ability to follow the instructions, a skill that is nevertheless useful for the future construction of flat pack furniture, but perhaps not a high speed rail line!

Tim Harvey (M), Garforth, Leeds

Editor’s note: While I understand your reservations around these Lego kits the answer is to simply buy a big box of plain blocks as well - and they’re much cheaper than the Star Wars models!

Lego vs Meccano

May I repeat what I said in a letter to you a couple of years ago:

“Lego is for bricklayers.

Engineers use Meccano.”

Colin Davies  (F), Heath Road, Potters Bar, Herts, EN6 1LR

Back to base

Surely Alisdair Beal’s argument  (NCE last week) is back to front.  Base load generation may be the easy bit, but it still has to be done and nuclear power is a dependable low-carbon means of achieving it.

The problem with most low-carbon energy sources (hydro and biomass excepted) is that they cannot even supply the base load reliably. If they could do that we would need fewer coal, gas and nuclear plants.

George Tedbury (M), 34 Springfield Drive, Calne SN11 0UG


Unlike Antony Oliver, do other long retired members share my misgivings over PFI projects? (NCE 19 February)

Under the system that applied years ago the major projects that I worked on - many of them motorway contracts - came in on time and on budget.

Against that record there are now too many works that seem to flounder under PFI initiatives; the new Wembley Stadium and the ever increasing debacle over the 2012 Olympics and their costs being two major examples.

All too often it appears that these projects are awarded with too little thought and too little preparation leaving the public to pay the bill for them for years into the future.

Royston Foot (F),

Boris Island

Douglas Oakervee’s view that “from an engineering perspective it is quite clear that the mayor’s ambitions could be realised”, (NCE 12 February) is to be respected, but reportage so far seems woefully short of discussion of two crucial issues.

Mr Oakervee’s words are probably very carefully chosen because relocation of employment and accessibility must surely be very powerful contra-indicators. Very large airports employ very large numbers of people on-airport, but there are also large numbers of airport related jobs off airport.

With these jobs goes the commercial infrastructure of the businesses that either must or choose to locate in close proximity to the airport. Potentially, all these businesses would have to relocate with the airport, but where to, how long would relocation take and what would be the economic impacts?

Accessibility affects airport related employment, all the people and services that support that employment and the people and goods that move through the airport. The High Speed shuttle line barely stands any hope of handling the very large number of workers and passengers seeking to access the airport from where they are now.

Does it really make economic or environmental sense to relocate Britain’s largest airport to a location that is so remote from its customer base?

Peter Fells,

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