An approach to securing high quality SuDS
Paul Baker, London Borough of Hammersmith & Fulham
Despite over half of H&F being in the Environment Agency’s Flood Zones 2 and 3 the borough is extremely well protected from flood risk from the Thames thanks to local river wall defences and the Thames Barrier. Only a breach of these defences would result in flooding from the river. Any risks of flooding are more likely from sewers/surface water which was the main motivation for a recent strengthening of planning policy in the council’s Local Plan, due for adoption in February 2018. The council has a reputation for leading the way in installing its own SuDS schemes in recent years, but we also need new developments to contribute to surface water management in the borough.
The new Policy requires SuDS measures in major schemes to reduce peak run-off to greenfield rates, however we don’t want this requirement to drive developers towards installing underground attenuation tanks as the default method of achieving this requirement. We also need SuDS to provide other benefits, so as well as being designed to minimise flood risks, our Policy therefore requires SuDS measures to be designed and implemented where possible to help deliver biodiversity benefits, water efficiency and quality improvements and recreation and amenity benefits. We are particularly keen to see rainwater harvesting systems and infiltration techniques used where these are feasible and expect major schemes to integrate living roofs (with blue roof storage where possible). We also require smaller developments to reduce surface water flows into the sewer, as all development proposals to provide a potential opportunity for the inclusion of SuDS, even if it is relatively small and simple measures such as soft landscaping, permeable paving and water butts.
Developers are encouraged to engage with the council at pre-application stage to make sure SuDS measures are well integrated at an early stage of scheme design. This should ensure an acceptable SuDS Strategy is submitted with the application from the outset. Strategies submitted with applications are expected to be as detailed as possible so we are clear what SuDS measures are proposed, where they will be on site, what levels of attenuation they will provide and how they will be maintained.
The aim is to achieve high quality SuDS measures that not only help reduce flood risks in H&F but also provide all the additional benefits that ‘above ground’ SuDS provide.