The Importance of Designing for Exceedance

As the environment changes – with an increase in frequency of extreme weather events as well as an ever-expanding population – it is crucial to ensure that your surface water management solution is designed to be able to meet the requirements of the ‘new normal’, not just the usual 1 in 30 rainfall.  This was certainly the case earlier this year when we saw a much higher than average frequency and duration of rainfall in many parts of the country but most notably in the Thames area.

Due to the effects of climate change and urbanisation, surface water flooding has increased and the drainage systems in place are being put under stress with excessive amounts of water from extreme events, which unfortunately we’re seeing more and more.

The traditional approach to combat this is to provide underground storage or build bigger pipes, a tactic which has been called by the Environment Agency, amongst others, both unsustainable and unaffordable. Instead, another approach is coming to the fore, managing flood risks in a more flexible way – designing for exceedance.  Almost by definition, at some point rainfall will exceed design capacity, so designing for exceedance is needed throughout the UK and not just those areas that have already experienced serious flooding.

Designing for exceedance, while making best use of existing urban areas, is a great way of dealing with the new, unprecedented levels of water – it’s about taking a more holistic approach to planning, designing and retrofitting drainage systems to cope with excess water. This can be achieved in a number of ways including simple topographical changes such as the use of flood pathways to manage runoff on highways and direct to storage locations; examples of these include swales or flow pathways around properties. Additional storage can also be built on the surface through the use of multifunctional detention basins, making the most of available open spaces. However, there is a potential issue with public perception of rain water not being taken underground ‘immediately’ as ‘flooding’ and therefore a failure of the system.

The idea of designing for exceedance has been endorsed by various organisations, has also been included in the government’s National Planning Policy Framework and was also a focus in CIRIA’s ‘Designing for Exceedance in Urban Drainage – Good Practice’, published in 2006. Despite this, the uptake level is low, in part perhaps because there is no obligation for designers to consider what happens when real rainfall exceeds the return period in the specification they have designed to.

Recent experience clearly demonstrates that the traditional way of managing surface water is no longer sufficient but how do we, in the drainage community, get public understanding that designing for exceedance can benefit them and the wider community?

ACO SuDS Swale Inlet: Behind the Design

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Bringing products to market involves a detailed journey of research and testing to develop a solution that meets various industry guidance and criteria.  In fact, many are developed to answer challenges presented by changes in legislation.  This was exactly the case with our SuDS Swale Inlet, which started as an initial response to Schedule 3 of the 2010 Flood and Water Management Act, evolving into the effective and noteworthy interface between SuDS solutions and proprietary drainage systems that it is today.

When reviewing the market’s requirements, a dearth of end of pipe solutions and a reoccurring trend of visually unappealing swale and basin inlets – often left as a cut pipe or with an unsightly concrete surround – was evident. Following customer suggestions and guidance from CIRIA C697, we recognised that a solution providing consistency of finish whilst being highly cost effective needed to be developed.

Engaging directly with our customers and meeting with landscape architects, local authorities, and environmental engineers across the country is always an integral part of our new product development programme, to ensure we create insightful solutions that meet the needs of the entire supply chain.

Taking on board wide ranging feedback we developed a solution that offers simple aesthetics with a technically advanced design in terms of surface finish and flared outlet.  As a result, flow is distributed across a footprint up to six times that of traditional pipe outfalls, allowing water dispersion and reducing scouring velocities.  What’s more, our SuDS Swale Inlet is the only product on the market that provides an off the shelf, ‘drop in’ solution for contractors, with erosion protection at the heart of it.  This product really takes swale inlets to the next level!

Click here for more information on ACO’s SuDS Swale Inlet.

Another step forward

ACO floodingIn the 2014 budget, revealed yesterday, the Government announced that an additional £140million would be spent following the damage caused by the recent floods.  This will take the total spend for repairing and rebuilding UK infrastructure up to £340million – £200million to fix potholes and the additional £140million will be used to repair flood defences.

As we are all too aware, the devastation caused by the recent flooding has been significant and it is good to see that more is being done to help avoid this in the future.  In some part, we have already seen the positive results of investing in flood defences and surface water management solutions.  If you compare the recent flooding to that of 2007, there has actually been significant progress. Then, ten times the number of properties were flooded than in recent months and the Environment Agency has estimated that over 800,000 additional homes have been protected by flood schemes this time round.

Funding is therefore just part of the story, it is also essential that there is an exhaustive examination into what has and hasn’t worked and how these situations can be avoided in the future.  We should also be using our experiences to identify best practice – not only in the design solutions but also in terms of the ways of working that have made a difference.

Now, let’s seek collaboration; where planners, designers, manufacturers, policy makers, budget holders, engineers and the general public input into an integrated approach, to ensure that we adopt best practice and spend effectively, within a timely framework of guidance and legislation.

To see how improvements have been made since 2007, take a look at our infographic.

Flood resilience – are we making a difference?

If you look beyond the recent headlines, some may be surprised to learn that, in many cases, the reach of the flooding impact has been reduced.

Our engineering and planning communities have made some progress – with those flood defences and surface water management solutions introduced unquestionably making a huge difference to towns all over the country.

Here’s a simple infographic we’ve put together that demonstrates the progress that is being made and the design solutions that are helping to create sustainable solutions.

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Launch of BS 8582 – a much needed step forward for practical, sustainable drainage

The recently published BSI standard provides a hugely useful ‘code of practice’ to those of us involved in the specification, installation or maintenance of surface water management systems.

One of the key topics recognised by the standard is the relevance of proprietary drainage systems, and how they can provide flexible, effective, and complementary alternatives to natural infiltration systems.

With space and ground conditions such a major factor on new urban developments, this acknowledgement of hybrid surface water drainage solutions will be a welcome development to designers and planners.

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BS 8582 recognises the use of proprietary drainage elements as part of a sustainable drainage system (SuDS)

And with the forthcoming legislation changes, BS 8582 also provides SuDS Approval Boards (SABs) with a structured methodology to assess drainage planning applications.

For more information on BS 8582:2013 Code of practice for surface water management for developed sites, visit the BSI website

Flood prevention plans delay – new controversy?

With the profile of flood prevention high on the agenda it seems to be the right time to be talking SUDS.

News on the subject has been building gradually over the last week or two and the article by Roger Harrabin on the BBC article makes for interesting reading http://www.bbc.co.uk/news/uk-politics-25676973

Extended range of flow control systems lower project costs

Our newly extended range of flow control systems can now regulate any surface water flow before it discharges into a watercourse or sewer network. The updated range includes both Q-Brake Vortex Flow controls and Q-Plate orifice plate systems which are designed for efficient handling of flows, simple maintenance and easy installation.

ACO's extended range of flow control systems

ACO’s extended range of flow control systems

ACO Q-Brake Vortex is ideal for flows up to 100 l/s and minimises maintenance with no moving parts and large openings to reduce blockage risk. The enhanced patented bypass door and emergency drain down facility enables remote access to the bypass inlet and independently drains the upstream system – simplifying access and removing the need for direct man access to sewer manholes.

In situations where the ACO Q-Brake Vortex is not suitable, ACO Q-Plate offers an effective alternative. Our orifice plates are available with or without remote bypass and drain down, and depending on your project requirements, are available with flat and round manhole configurations to simplify installation.

Our design team will provide guidance to ensure the right product specification and both flow control systems are included in the WinDes software to simplify hydraulic modelling. Manufactured from stainless steel, the systems offer high quality, yet robust, reliable and economic solutions. With rapid deliveries to exact site requirements, our range of flow control systems will reduce installation costs, minimise maintenance and will ensure the final stages of a project can be concluded quickly and without hassle.

For more information on our range of flow control system visit the ACO website.

 

Design power in your hands

Our extensive range of channel drainage means we have a system for any application, however choosing the correct channel size to convey the flow from the drained area can be less clear….

The ACO Hydraulic Design Software is designed to answer just this.

The free online tool accurately analyses your selected channel to check it has suitable capacity; furthermore it can optimise the selection and potentially downsize the system if it is oversized.

ACO Hydraulic Design Software on a tablet

ACO Hydraulic Design Software on a tablet

Discover how our design software allows you to create more effective hydraulic plans – visit www.acodesign.co.uk

Scottish wildlife protected using our Wildlife Kerbs

Our Wildlife Kerbs have been used on a scheme in a Perthshire town to help prevent local wildlife being washed down the drain.

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During migration, amphibians will often follow the kerb line and it’s staggering to hear that in this county alone, an estimated 47,000 could fall down a road gully and become trapped!

Our Wildlife Kerb has a built in recess which allows amphibians to continue on their natural path but avoid the danger of a road side gully.

Watch this video from ARGUK to see how Perth and Kinross Council have been piloting the use of these kerbs to help the local wildlife.

ACO StormBrixx nominated for an award again!

Its smiles all round here at ACO– last month ACO StormBrixx was again shortlisted for an award.

This time it was for the highly regarded Sustainability Leaders Awards in the category Sustainability Innovation: Systems & Software. The awards recognise organisations that are making genuine progress in embedding sustainability throughout their operations and we are thrilled to be part of the cut!

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Since its launch in 2012, the success of our geocellular stormwater management system, ACO StormBrixx, has been tremendous. In October 2012, its clever design was affirmed when presented with the prestigious British Construction Industry (BCI) Awards for Product Design Innovation.

Since then it has been recognised by the CPA in their Innovation & Achievement Publication, and has been shortlisted in both the Sustain’ magazine and the Environment and Energy Awards.

The industry recognition of its clever design and successful application in numerous projects confirms it is the special product we were aiming for. Its success has proven that it is something that brings value engineering, delivers real benefit and solves many challenging issues for successful, sustainable surface water management today and for the future.

Head to the edie.net website for more information on the Sustainability Leaders Awards