Sewer flooding, in which the sewer network becomes overwhelmed during intensive rainfall, is a distressing, unpleasant experience for customers, as well as posing an environmental risk.

Intensive rainfall is becoming an increasingly common feature of modern weather patterns, and in response, we must adapt our sewer network and the way we manage it.

Rainfall in the years to come

We expect the rainfall to change over the next 25 years with wetter winters and drier summers with more intense storm events. This can be seen in the graph below:

Ranfall graph

It’s important to recognise, however, that there is a limit to how much we can achieve, while keeping customers’ bills affordable. Working with partner organisations to tackle this issue from several different angles is vital – as upsizing every length of sewer pipe to increase capacity is simply cost prohibitive.

The number of homes affected by sewer flooding reduced in 2013/14 when compared to 2012/13, (down from 906 to 451), which is within the expected range for a good performing company of our size.

Nevertheless, we recognise that we still have more to do in this area and have plans in place to continue bringing the number of flooding incidents down.

Key areas of focus include:

Investing in our network: we are investing money to increase the capacity of the sewer network in areas prone to flooding. Last year we spent around £35 million on 30 projects, removing 170 properties from the flood risk register – a list of properties in our region which have suffered sewer flooding in the past, or are believed to be at risk of flooding.

More efficient management of our network: using a centralised system which receives information from remote monitoring devices, installed on our pipes, allowing us to respond more quickly to issues, identify problem parts of the network and predict future trends with greater accuracy.

Mitigation team: our sewer flooding mitigation team investigate sewer flooding incidents, and where possible, fit protection devices to minimise the impact of sewer flooding. Since 2009, the team has helped to protect over 1600 properties. Last year, they helped to remove 28 properties from the flooding register by providing advice and measures such as anti-flood air bricks, disconnecting cellar drains, raising doorways and providing flood proof doors and gates.

Working in partnership: the root causes of flooding are often complex and we often cannot resolve issues alone. Our work is part of a wider jigsaw involving many partners. We continue to freely share our data and expertise with other organisations and contribute to local plans to manage flood risk in different geographical areas across the North West.

Supporting Sustainable Urban Drainage: we’ve been assisting Defra in the drafting of National Standards for Sustainable Drainage Systems (SuDS) and supporting guidance documentation. The rules will ensure new building developments include features such as soakaways, permeable pavements and ponds to capture or slow down rainwater run-off and ease pressure on the sewer network. We’ve incorporated these principles into our own infrastructure projects. An implementation date for the new national standards is still pending.

If you would like to send us a comment about this report, please email our Head of Sustainability, Chris Matthews