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Reducing flooding and improving resilience

Urban creep – the conversion of existing permeable areas – has increased significantly over the last ten years. According to the Royal Horticultural Society (RHS), the proportion of front gardens that are completely paved over in the North West increased from four per cent in 2005 to 21 per cent in 2015. Back gardens have also been built on, with new extensions and conservatories that may then be connected into surface water drains.

Surface water run-off from new developments and urban creep leads to higher peak flows in the sewer system. This leads to a higher risk of sewer flooding, and increasing frequency and duration of intermittent overflows to watercourses.

In order to protect customers and the environment, there is a need to reduce flooding and spills, and improve the resilience of the sewer network to cope with peak storm events. We need to do this in a more sustainable way than traditional interventions, such as storage tanks and upsized sewers, which is why we are taking a positive approach to sustainable drainage solutions (SuDS) for surface water management.

Slow the flow garden

We are working with partners (City of Trees, RHS) to transform hard grey areas into living, planted places. So far we have initiated several key SuDS projects, including our show garden at RHS Tatton in 2017, which demonstrated how a front garden could be designed to contain sustainable drainage solutions instead of traditional hardstanding areas.

Our 'Slow the Flow' garden, designed by John Everiss Design Ltd and Francesca Murrell, received excellent feedback and won Best Show Garden at Tatton 2017. It has since been relocated to Moss Bank Park in Bolton, which is open to the general public, to help increase the numbers of customers that can be informed about sustainable surface water management.

Informing our customers

There are, on average, 75,000 visitors to Tatton flower show every year, with 63 per cent being from the North West (more than any other RHS show). The show receives television and radio coverage and is also widely promoted using social media.

This project therefore contributed significantly to educating and influencing customers on surface water management at a household level, particularly relevant for new developments and surface water run-off, and provides us with information on the cost and feasibility of this type of solution. It helped highlight to household customers the impact of urban creep on downstream flooding, and educate them on how they can play their part in reducing peak flow to combined sewer systems.