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Adaptation and resilience – how to deal with too much water?

Thames Water Employee



We must deal with whatever weather happens on a daily basis, and this included the impacts of severe weather. Since 2010 we’ve put a lot of effort into improving our understanding of how climate change could affect our ability to deliver essential services to our customers.


It is widely accepted that climate change is a serious issue and a major challenge to society; however, it is almost impossible to predict the extent and timing of its impact. We have nearly 7000 operating sites providing the essential water and wastewater services to 15 million customers and we don’t want to invest at these sites inappropriately or at the wrong time. This makes planning for issues extremely challenging.


Following a review of the potential impacts of climate change on the business, we identified that our key issues are still broadly associated with either too much or too little water. Today's blog focuses on our response to "too much water", which includes flooding resilience and sustainable drainage systems (SuDS).


Two of our current performance commitments agreed with our regulator Ofwat include increasing flooding resilience of water (WB8) and wastewater (SB7) services for customers. We’re working hard to protect our sites from flooding. We’ve assessed our water and wastewater sites for how the might be impacted by river and surface water flooding associated with a 1 in a 1000-year event. This is to help us understand how much and where flood water would be in relation to our assets. This has helped us to better define the risks at each site and to develop more detailed investment planning needs. Through a number of schemes at our wastewater sites, we have managed to cover 962,842 population equivalent so they have a flood resilience standard of a 1 in 200 year event. 


Our area is in one of the most densely populated and urbanised regions in the UK, which places a lot of pressure on drainage. Heavy rain can overwhelm our sewers, so whenever possible, we take advantage of opportunities to deliver more SuDS to increase our sewer capacity, encourage natural drainage and reduce and slow the flow of surface water into our network.


In 2015, we launched a SuDS programme to disconnect 20 hectares of impermeable land from the combined sewer network - one hectare is roughly the size of an international rugby pitch – and we’re on track to deliver this target. Between 2020 and 2025 we’re looking to more than triple our target to 65 hectares, providing a wide range of benefits to our customers beyond that of improving asset resilience.


Nine Elms is the UK’s biggest SuDS project. With our partners we’ve been installing ambitious and innovative SuDS to ease the pressure on the existing sewerage system as a result of a number of high-profile projects planned in the Nine Elms area of Vauxhall, South London. Instead of running into the sewer network, the rainwater which falls on the area between Vauxhall and Battersea Power Station will be channelled into large underground pipes which will then be discharged into the River Thames. This big engineering project will be complemented by a variety of eco-friendly innovations in the new housing developments, including green roofs, ditches containing filtering vegetation, and streets with rainwater gardens. These will allow water to evaporate into the atmosphere, irrigate plants, and reduce the volume of rainwater flowing into the river.


By keeping much of the rain water out of the sewers, we’ll have extra capacity to serve new developments and improve our resilience to floods in the downstream sewer network. We can also reduce the size of the sewer pipes needed, as well as the associated pumping and treatment requirements.