Flood control needs a collaborative approach

Dr Jason Shingleton is marketing and development director at Polypipe Water Management Solutions (WMS). We caught up with him to discuss the latest sustainable drainage and water management issues.

WN: The UK drainage system cannot cope with flash flooding. What needs to be done in the short-term to combat this increasing problem while the industry waits for legislation and report recommendations to be implemented?

JS: New build projects already include a flood risk assessment as part of the planning process in accordance with PPS 25 (Planning Policy Statement 25: Development and Flood Risk), which should ensure that new developments do not add to the risk of flooding. However, consideration also needs to be given to refurbishment projects to ensure they come under the same scrutiny.

As part of the flood risk assessments it is common for discharge limits for surface water run-off to be set from new sites into the existing drainage system, which has led to the growing use of engineered sustainable drainage systems (SUDS) over the past few years. These solutions aim to mimic the conditions of an undeveloped site by allowing the excess stormwater to either soak away or attenuate on-site, reducing the impact of flooding on developments downstream.

For existing developments there is no easy option for flooding prevention, unless additional flood defences are installed or – if ways can be found – SUDS are retrofitted. This involves controlling a percentage of the surface water that currently discharges to the sewer network, redirecting it to an above-ground solution or engineered soak-away or attenuation structure below ground. Retrofitting rainwater harvesting is also a good way of providing some control by reusing the water captured from roof areas within the building.

WN: What can be done to encourage homeowners to either stop concreting over their gardens or to find a sustainable solution that allows surface water to drain?

JS: Education is the key area. Homeowners need to understand the impact of turning permeable and porous surfaces into hard-standing areas. What will make a big difference is understanding the alternatives in terms of SUDS, such as porous paving and modular cells underneath the paved or concreted areas for use as attenuation or a soak-away.

Changes to the planning guidelines in October 2008 mean that planning permission is now required for any hard standing area of more than 5m2 created by paving over a front lawn or landscaped area (and this could be extended to cover rear gardens and patio areas), although this needs to be fully enforced to have any real impact.

Government could follow an example set in the US where some states tax properties according to the amount of impermeable and hard standing area within them, although this is quite a hard-line approach. It is important to remember that consumers are unlikely to react positively to enforced changes without clear information or an explanation of the benefits.

WN: The Pitt Review, Floods and Water Bill, and government strategy Future Water emphasise the need for a coordinated approach. What do the water companies and their supply chains need to do to achieve this? Who should lead this (Ofwat, the EA etc)?

JS: It is hard to be certain who should lead the coordinated approach. The Floods and Water Management Bill in particular requires a national perspective, so it is likely that the Environment Agency will assume a strategic role and be in charge of setting the regulatory framework. This is more appropriate as it is a national body and can work across local boundaries to set national policy. It is also ultimately responsible for flood prevention and warnings.

The upper tier of each local authority is likely to be required to create regional stormwater management plans, and these are probably the best people to pull together the coordinated approach.

To get all agencies to work together there needs to be a clear framework of responsibilities with regards to the planning, design, adoption and maintenance of drainage systems, including sewers and SUDS. It is vital that each agency understands its role in developing the surface water management plan, otherwise this will lead to a confusion in responsibilities and the allocation of appropriate resources.

WN: According to the Pitt Review, local authorities should approve and maintain sustainable drainage systems. Is this a viable solution?

JS: Yes. It is a viable solution for local authorities to be responsible for the approval, design and maintenance of SUDS, as they are already responsible for planning applications. The Floods and Water Management Bill requires an appropriate drainage solution to be determined at the earliest stages of the planning process, and this will ultimately enable greater design flexibility.

Local authorities currently have the ability to maintain above-ground solutions such as ponds and swales and are involved in assessing drainage systems within the Building Regulations. However, the issue in many cases is that they lack specific sustainable drainage design and installation expertise to deliver the requirements of the Floods and Water Management Bill.

Local authorities may need to acquire the necessary skill-set through recruitment and training, or they may need to subcontract the SUDS approval process to consulting engineers with the relevant experience. Either way, this gap in resource will take time and money to fill.

WN: What have other countries done in terms of implementing long-term sustainable drainage strategies? Are there lessons to be learnt?

JS: Yes. The UK is still somewhat behind the US, Germany and Holland in its adoption of SUDS strategies. The US has the LEED (Leadership in Energy and Environmental Design) system in some states that deals with managing both the quantity and quality of surface water run-off. This encourages the use of above-ground water management solutions, but also drives innovation in engineered solutions that treat, store and control excess stormwater.

Germany makes far greater use of rainwater harvesting and porous pavement solutions to manage water. The German government offered grants to homeowners to install rainwater harvesting systems early on in the process, thereby incentivising the market when paybacks were low. SUDS best practice in Holland tends to utilise innovative drainage solutions, with water often being kept at the surface before being controlled. But whether this approach would be accepted in the UK, where public perceptions and requirements are different, is yet to be seen.

WN: How is Polypipe working / collaborating with the water / construction sectors to ensure its products are at the forefront of innovative sustainable drainage solutions?

JS: Our Water Management Solutions (WMS) team was set up in 2007 in response to the growing legislation that impacts on the use of SUDS. By working closely with industry organisations and government, as well as consultants, engineers and contractors, we are working proactively to provide holistic solutions that can be combined to offer the market a choice of the most appropriate products to meet the specific requirements of a project.

Ongoing product development and innovation is an integral part of our strategy, and we now offer the most in-depth portfolio of SUDS products (including all third party assessments where possible), including the latest developments to our Polystorm modular cell ranges, Ridgistorm-XL large diameter pipe and the Storm-X4 treatment filter, which control both the quantity and quality of surface water run-off.

By looking at sustainable water management from a ‘Roof to River’ perspective, we can offer a wide range of engineered, below-ground products and solutions for any SUDS requirement, from siphonic drainage through to storage, treatment and discharge.

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