Thames sets out £32bn drainage plan

Thames Water has detailed how it will tackle surface flooding and reduce sewage discharges in London and the Thames Valley with a 25-year plan, which it estimates will cost £31.9 billion.

The drainage and wastewater management plan (DWMP) addresses long-term risks to properties, communities and infrastructure from population growth and climate change as extreme weather brings heavier, intense rainfall.

The National Infrastructure Commission (NIC) described surface water as the greatest flooding threat, but the least understood.

Around one-third of the investment, £10.9 billion, will be directed to combating the risks of harm from combined sewer overflows (CSOs) as part of commitments to improve rivers and streams.

The DWMP is made up of 13 catchment strategic plans, which prioritise nature-based solutions wherever possible. This includes adding 7,000 hectares of sustainable drainage systems (SuDS) in London.

“From creating more spongy and green spaces to helping prevent flooding in peoples’ homes, we want to take action to stop rainwater getting into the sewers in the first place,” chief executive Sarah Bentley said.

“However, there are no quick fixes and this plan is the start of our journey to ensure we have systems which are fit for the future. Working collaboratively with our partners will make a big difference to wastewater activities for future generations and our precious environment.”

The company separated out the capital from the Thames Valley region with bespoke plans based on customer and stakeholder engagement for each area.

For London, the plan focuses on SuDS to redirect surface water away from combined sewer networks. It will include adding water butts across the city, rain-gardens to roads and urban spaces, swales and ponds in parks as well as creating wetlands and restoring rivers.

Compared to the amount of SuDS delivered in recent years, adding 7,000 hectares of drainage is ambitious.

Alex Nickson, wastewater systems strategy manager at Thames, told Utility Week earlier this year that the company had to shift “from a reactive, opportunistic approach to a target-driven outcome focussed mentality, achieved through improving new developments, retrofitting existing urban areas and encouraging and incentivising Londoners to unwind the urban creep that has been enabled over decades.

Outside of the capital, the plan prioritises removing unwanted flow by stopping water entering sewers from misconnections, groundwater infiltration and from surface water drainage.

The plan will be updated every five years as part of the 25-year vision