Sustainable Drainage In Hammersmith and Fulham

On 28th June, members of the FPS team attended a Summer SuDS Tour with PROSPER and the Environment Agency around Hammersmith and Fulham.

This reflects the type of work we are increasingly involved in across the capital, delivering Flood Risk Assessments in London alongside surface water drainage strategies to support safe and sustainable development.

Sustainable Drainage Systems, or SuDS, is a way of managing rainfall that mimics the drainage processes found in nature and addresses the issues with conventional drainage.

The original timetable for the implementation of Schedule 3 of the Flood and Water Management Act, which would have made SuDS mandatory on most new developments, has been deferred. While Schedule 3 awaits formal commencement, the December 2024 update to the National Planning Policy Framework now requires SuDS to be considered for all planning applications affecting drainage on or around a site, expanding the previous threshold which only applied to major developments. Our team is well placed to provide Surface Water Drainage Strategies and Detailed Drainage Designs for projects of all scales.

Hammersmith and Fulham has been proactive in recognising the role of Sustainable Drainage in town regeneration areas, with commendable foresight in incorporating SuDS into ongoing public realm work.

The borough has some sizable open spaces and parks, but as a densely-built urban area it also has substantial impermeable surface coverage. It contains a significant number of basement properties that are particularly vulnerable to surface water and sewer flooding. Nearly all of the borough’s drainage infrastructure is a combined sewer system, operated by Thames Water.

Before the universal adoption of piped drainage, it was common to convey runoff across the land surface directly into ditches, streams and local rivers. With the growth of Victorian cities and the development of piped drainage, human and industrial waste together with rainwater runoff from buildings and streets was directed into a single underground pipe — the combined sewer. In periods of heavy rainfall, combined sewer overflows (CSOs) act as relief valves when flows exceed sewer capacity, discharging untreated sewage into local watercourses. Many British cities and towns of Victorian age are served by combined sewers, which is a significant cause of pollution in our rivers and seas. Incorporating SuDS is therefore vital to reduce the overwhelm on combined sewer networks.

Conventional drainage seeks to remove runoff from development as quickly as possible. In contrast, SuDS slow the flow and store water in both hard and soft landscape areas, reducing the volume and improving the quality of water flowing from development.

The Hammersmith and Fulham tours are arranged as part of the programme funded by the Thames Regional Flood and Coastal Committee (RFCC). The committee has identified £1 million of levy funding to deliver the PROSPER project, which stands for Protecting People, Property and Environment with SuDS. The overall aim of the project is to promote the adoption and delivery of SuDS, streamline the assurance process, and provide evidence to inform alternative funding mechanisms for Flood Defence Grant in Aid (FDGiA).

It was particularly useful to see the schemes delivered in Hammersmith and Fulham, including the maintenance regime since installation and how the benefits are being monitored. Examples like these can serve as a blueprint for SuDS implementation projects nationwide.