Southern Water supports the overall intention of this policy to manage flood risk, in particular the requirement for new development to incorporate sustainable drainage. Until Schedule 3 of the Flood & Water Management Act is implemented, S106 of the Water Industry Act continues to confer a right to connect surface water to the combined sewer network. Therefore, to increase the effectiveness of this policy we would encourage the prevention of, or at very least a resistance to, any connection of developments’ surface water drainage to the foul or combined sewer network. This is to minimise the risk of sewer flooding, and increase available capacity for foul drainage.
Whilst some parts of the sewer network were originally designed to accommodate surface water, the expansion of towns and cities, in particular of ‘urban creep’ can exacerbate capacity issues. As stated in Water UK’s 21st Century Drainage Programme; “The country’s built environment is constantly changing and “urban creep” – home extensions, conservatories and paving over front gardens for parking – can all add to the amount of water going into our sewers and drains. Green spaces that would absorb rainwater are covered over by concrete and tarmac that will not. In fact, studies show that “urban creep” results in a larger increase in predicted flooding than new housing, because it adds more rainwater to these systems’.
Therefore it is also recommended that any areas utilised for SuDS should be safeguarded from future alterations or development that would impede their effectiveness.
Preventing surface water from entering the foul and combined systems during heavy rainfall is also the most sustainable and cost-effective way to reduce storm overflows. Southern Water is investing heavily in work to reduce their use across its region (see southernwater.co.uk/water-for-life/clean-rivers-and-seas-plan/map), in part by removing existing connections of surface water to the combined and foul networks.
We therefore support, with suggested additional wording, this policy’s approach for its contribution to reducing the risk of flooding and pollution, in line with paragraphs 166 and 180(e) of the NPPF.
Proposed amendment
‘All planning applications for major development are required to ensure that Sustainable Drainage Systems (SUDs) are used for the management of surface water unless demonstrated to be inappropriate. All new developments in areas at risk of flooding must give priority to the use of sustainable drainage systems, and connection of surface water to the foul or combined sewer network will be strongly resisted.’