One of the most important environmental challenges facing the UK is how best to deal with extreme weather conditions, particularly bad cases of stormwater. Following the severe flooding that parts of the UK experienced in winter 2012, it is becoming increasingly clear that the most effective course of action would be to prioritise planning for how to manage these situations in advance. Here, Terry Sloman, Regional Sales Support Manager, Burdens Utilities, will discuss the key considerations around stormwater management and how to prepare for extreme weather by future-proofing properties and developments.
The subject of stormwater management is fast becoming one of the UK’s primary concerns in the area of environmental issues we need to be prepared for. According to the Department for Environment, Food and Rural Affairs (DEFRA), more than five million properties in the UK are at risk of flooding, which equates to one in every six homes in the UK (1). Meanwhile, the UK government has recently published its National Adaptation Programme (2), detailing plans to enhance the UK’s resilience to a changing climate and increasing weather extremes. Yet, while the government has announced that it is taking measures to better protect more than 64,000 more homes through 93 new flood defences (3), the £294m scheme has been criticised for favouring the ‘big cities’ rather than rural areas that were significantly hit by high levels of flooding in winter 2012.
It is becoming ever more apparent how important it is to anticipate and manage severe flooding situations. Since rain records began in 1766, the amount of rainfall has continued to increase in the UK. In 2000, UK flooding was at its worst for 270 years in many areas, and in 2009 some areas such as Cumbria witnessed widespread flooding. It is estimated that flood damage costs the UK more than £1 billion (4). High volumes of stormwater run-off placed increased stress on existing drainage systems and urban watercourses. When a previously undeveloped site is built on and paved over, stormwater run-off from the newly impermeable surface increases by up to 80 per cent, which places greater pressure on existing watercourses and drainage infrastructure. This can lead to downstream flooding, localised erosion, the destruction of habitats and combined sewer overflows. The traditional means of dealing with increased stormwater is just not viable anymore.
This problem is not only limited to the UK. Australia is pressing ahead with its Water Sensitive Urban Design (5) initiative, following a series of floods and some of the worst droughts recorded in history. These affect the health, well-being, safety and productivity of the population, and the result is an awareness about the impact of stormwater that is now considered in all development planning and policy responses to climate change. Joining up the water cycle and making better use of rainwater will help significantly reduce the risk of water stress on developments and the health and safety of the general public. The UK is catching up to this way of thinking. A recent report by the Construction Industry Research and Information Association (CIRIA) in March states: ‘Water shortages, flooding and watercourse pollution are all signs of stress where developed areas have a troubled interaction with the natural water cycle and where, conversely, water has become a risk or nuisance rather than an asset or opportunity.’ As we move forward, we need to acknowledge the challenges that stormwater presents, but then consider how we can future-proof new and existing developments to cope with these growing pressures, and harness water as an opportunity.
Flooding has a dramatic impact on people’s lives. Ever since the Pitt Review in 2007 (6), the importance of considering surface water risk has become enshrined in a development’s planning stages. The report identified some of the key issues that needed to be addressed and the lessons learned following the floods in the summer of 2007. These include maintaining power and water supplies, protecting essential services, providing better advice and help to those affected by flooding, and ensuring the highest standard of resource and care is delivered. However, to improve our ability to withstand the levels of flooding witnessed in recent years, section three of the Pitt Review, entitled ‘Reducing the risk of flooding and its impact’, should still be the top priority.
The latest Sustainable Urban Drainage Systems (SUDS) have been developed to cope with the demands that heavy rainfall can place on an area. Indeed, integrated systems incorporating attenuation tanks, large capacity drainage channels, lagoons or ponds, porous paving and rainwater harvesting are now an essential part of any new development. Fully-integrated SUDS is a combination of several product systems that form an end-to-end solution that guarantees performance, while offering the customer optimum value. The solutions available include stormwater infiltration modular cells, large diameter pipework, separation tanks and flow control regulators.
In order to achieve smarter stormwater management, a collaborative relationship between all stakeholders is required. Nevertheless, the benefits this will realise are numerous. Urban regeneration will improve public open spaces and surrounding buildings, plus there is even the possibility of using surface water to create features that form part of the urban realm. This will lead to long-term benefits: enhanced public spaces, greater biodiversity and increased land value. It is our responsibility to take action for delivering a more effective stormwater management strategy in the UK today, to improve our quality of life in the future.
- DEFRA, ‘Reducing the threats of flooding and coastal change’, http://www.gov.uk/government/policies/reducing-the-threats-of-flooding-and-coastal-change
- HM Government, ‘The National Adaptation Programme: Making the country resilient to a changing environment’, http://www.gov.uk/government/uploads/system/uploads/attachment_data/file/209866/pb13942-nap-20130701.pdf
- BBC News, ‘Construction to start on 93 new flood defences’, http://www.bbc.co.uk/news/uk-21364056
- The Environment Agency, ‘Flood and coastal risk management in England: a long-term investment strategy’, http://cdn.environment-agency.gov.uk/geho0609bqdf-e-e.pdf
- Melbourne Water, ‘Water Sensitive Urban Design’, http://wsud.melbournewater.com.au/
- The National Archives, ‘Pitt Review 2007’, http://webarchive.nationalarchives.gov.uk/20100807034701/ and http://archive.cabinetoffice.gov.uk/pittreview/thepittreview/final_report.html
Further product information
Storm water Infiltration Modular Cells: these are structurally strong box or cell shaped units . Modular cells offer a void ratio in excess of 90%, compared to a traditional system, such as rubble-filled soakaways, which offer only 30%. These cells can be built to form a shape of any size or depth. Their purpose is to form a holding tank for the collection of storm water for any hard standing surface run off on site. This tank can act in two ways. The first is to release the water back into the surrounding soil. This is achieved by wrapping the tank in a permeable geotextile. This system is known as a soakaway. The second system is to wrap the tank in a non-permeable geotextile and form a holding tank that will release the water within set discharge limits. This system is known as an attenuation tank.
Large Diameter Pipework: this system uses pipework for surface water storage and water management. Pipe sizes range from 600mm up to 3000mm. Pipe in its traditional use can be over-sized for its application which will allow storage capacity in times of need. Large diameter pipe is used as a storage tank by capping off the ends of the pipe to form a tank, where the water can be released within the set discharge limits. Plastic Pipework can provide bespoke manhole solutions and catchpits. They offer a one piece unit that is totally water tight and light, with large savings on labour installations.
Separation Tanks: these are storage tanks that provide treatment of rainwater on site. Full retention tanks are used where there is a high risk of regular contamination of rainwater. By-pass tanks” are used when there is a smaller risk of contamination. An example of where a by-pass may be used is a short stay car park. Both systems fully comply with the Environment Agency’s PPG3 and European standard EN858-1.
Vortex Flow Control Regulators: these are units used on end-to-end solutions to provide a buffer system that slows an upsurge of water in the system. Dry weather flow passes unhindered through the unit. When upstream water increases, with heavy rainfall, air is trapped in the upper part of the unit. Due to the internal shape of the unit, the water forms a vortex as the air is trapped, slowing the potential energy of the water by rotation. The unit then allows air back in. This destroys the vortex and allows the water to continue on its way at a slower rate. These units can be designed for each project, providing a bespoke unit.
The above systems should be used in conjunction with products used daily with the civil arena:
- Channel drainage
- Pervious paving systems
- Solid wall pipe systems: plastic/clay/concrete
- Structured Wall pipe systems: twinwall
- Land drainage