This week’s hot topics include Sir Philip Dilley’s resignation as Environment Agency chairman, the value of upper catchment management in flood defence and the worth of contractor in-house design teams.
Dilley’s testy resignation
The job advertisement adjacent to your article on Sir Philip Dilley’s resignation as Environment Agency chairman is for full time flood risk consultants at a salary of £33,000-£40,000. Dilley obviously has a very high opinion of himself if he considers that he has a lot to offer in three days per week at £100,000 with no operational responsibility.
Pickering showing the way
It was interesting to read of Pickering’s escape from the recent flooding, through abandoning the concept of building ever bigger walls; a confrontational approach of defence. Instead they worked to manage the way the storm waters were allowed to disperse.
I’m up for the challenging the accepted concepts, exploring the potential for sacrificial features designed in, green space that replaces the over-use of hard landscaping, and challenging the conventions which block cost saving use of infrastructure in different - and often forgotten but historically proven ways.
The bridges we knew as Irish bridges, reflecting an Irish pragmatism of building a bridge that crossed the basic stream or river but saved the expense of flood arches and the ultimate spectacle of bridges collapsing as they failed against the water pressure on solid spandrels and parapets; Irish Bridges being planned to go underwater in flood conditions without falling down.
This pragmatism is often seen on old roads crossing river flood plains where a raised walkway runs alongside a road which goes underwater in floods.
Further pragmatism might be to design key roads to provide flood relief channels, able to carry say 150mm depth of slow flowing water (which can be driven or waded through). A quick calculation suggests that a typical 7m to 8m wide single carriageway road flowing steadily with 150mm of water should move a substantial volume. Car parks and public open space in towns should also be designed as sacrificial attenuation reservoirs, a detail which Uckfield recognised some years ago.
Of particular benefit has been constructing paths beneath busy roads and railways, eliminating the need to cross these at grade, by sharing the bridges over streams and rivers. In the Highlands, the 3m to 4m wide Armco culverts required to handle meltwater flows have a trickle of a stream for 50 to 51 weeks per year - and when they are flowing full bore the needs of walkers and cyclists to cross the road is likely to be greatly reduced. The Dutch have this sorted with the main footpath under Utrecht station around a metre below the canal which goes under the same bridge.
With around 50 years of engaging with transport and engineering in a variety of ways, and often challenging the conventions, I’d be keen to work with the willing.
Before we can say the Pickering scheme prevented flooding we need to know the rainfall intensity it experienced. Was the Pickering catchment subject to the same record levels of rainfall that caused flooding elsewhere?
Dubai cladding concerns
It is concerning that fire spread across the external cladding seems to be so fast and uncontrolled. The specification of this type of cladding must not allow fire spread so easily.
Do engineers have influence?
I have been looking through some of my old files recently, trying to reduce the volume of papers I’ve retained. I came across a “Proceedings of the Institution of Civil Engineers - Special Issue”. The title was “Floods – a New Approach”. The date of this very earnest document? May 2002.
This raises the question – what have we been doing for the past 15 years? It seems that either we haven’t yet learned our lessons, or we haven’t managed to persuade our political masters that we know what we are talking about, and that they ought to take notice.
Perhaps this is the most telling point – politicians do seem to ignore our advice. Another case is surely the recent closure of the Forth Road Bridge, where concerns were raised some time ago about the robustness of the particular element that failed, and nothing was done about it until too late.
Perhaps our senior Institution members should be approaching those just down the road in Westminster and telling them that our voices are worth listening to.
Andy Whatmore (M)
Contractors and designers
Peter Gosling challenges your assertion that the contractor used in-house designers in the delivery of the Second Severn Crossing (NCE 26 November 2015). In fact you are both right. At the time the design was carried out, SEEE was a wholly-owned subsidiary of GTM, Laing’s construction joint venture partner. Perhaps the acclaimed success of the project was due in part to the combination of in-house SEEE and the independence of Halcrow, coupled with the complementary skills of British and French engineers.
SEEE now trades independently as Ingerop and recent trends indicate that, as the design & build market has matured in the intervening years, contractors are increasingly looking to divest themselves of the design function and return to the supply chain model.
Andrew Yeoward (F)