Water & Wastewater Treatment Magazine
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www.wwtonline.co.uk | WWT | AUGUST 2016 | 27 In the know Digging deeper: property-level flood protection Watertight strategies A whole catchment approach to tackling flood risk should include protection at the level of the individual property AlAstAir Moseley HonorAry Vice PreSidenT ciWeM T he catchment-scale flood events that we have regularly seen across the UK since 2000 have highlighted the complexities of providing flood protection in towns and cities throughout the country. Responsibility for managing flood risk in England lies with many different agencies, o•en working to different standards of protection, and this makes managing and funding flood mitigation measures a challenging process. When flood mitigation part of catchment-wide planning, and ultimately preventing damaging and expensive water ingress to properties. The use of Property-Level Flood Protection (PLP) measures is one such innovation and is an effective and affordable way of achieving this. Whole catchment approaches to flood risk management It is widely recognised that to provide complete protection against flood- ing is impractical and unaffordable. To achieve this, flood defences to rivers would have to be so high that they would have a detrimental visual impact for communities. Channeling flood waters beneath towns to avoid inundation of property simply by the use of larger drainage systems would be highly disruptive to construct, and the finite size of pipework would always lead to some residual flood risk being present. So rather than simply defending at the point of flooding, the deployment of whole catchment measures at different levels is now being seen as a far more attractive, practical and affordable way of protecting communities. Increasingly powerful computer modelling shows us that holding some flow back in the outer reaches of catchments, slowing the flow down to reduce accumulation, and absorbing surface water by the use of sustainable drainage measures in urban areas, is an effective way of reducing flood volumes to more manageable proportions. A third component to deal with residual flows would then be less intrusive flood mitigation structures including demountable flood barriers alongside river channels. Balancing capital investment to achieve positive outcomes Even with these measures in place, properties in the lower reaches of catchments or near to rivers and water courses will still be at risk in the largest storm events, as seen in the 2015/16 floods in Cumbria and Yorkshire. It is simply not economi- cally or physically possible to reduce flood volumes sufficiently to keep flood waters below property door thresholds in these locations during very large storm events. So a fourth component of flood mitigation is needed, which is to deploy flood mitigation measures at the properties themselves, otherwise known as Property Level Flood Protection (PLP). This takes the This sealed, flood-proof patio door is an example of PLP in action (Photo: Whitehouse) measures are progressed, affordability o•en limits the scale of flood mitigation measures that can be put in place, leaving a residual flood risk in extreme events. Flood risk is detrimental to personal health and wellbeing as well as to the local economy, and yet solutions to flooding o•en exceed affordable cost, leading to delay and prolonged suffering. This can only be overcome by adopting innovative approaches to flood mitigation as