We strongly support the inclusion of sustainable urban drainage solutions within this policy. However, we suggest some additional wording to help ensure this policy is effective in delivering appropriate surface water management.
Requested additions:
We note the following wording in this policy, and suggest additional wording for your consideration here:
• The proposal works with the topography of the site and the inventive incorporation / use / interpretation of existing natural features. Existing surface water flow routes and drainage features within the site should be identified and preserved wherever these contribute to sustainable drainage eg ditches, seasonally dry watercourses, historic ponds.

Further explanation and justification:
Southern Water supports all policy requirements which seek to ensure that surface water is appropriately managed, as close to source as possible and has made representations across related policy. We also need to ensure that design of developments will not mean that existing surface water drainage routes are not impeded to result in flooding elsewhere. This is in line with paragraph 167(c) of the National Planning Policy Framework (NPPF) (2023) that requires:
using opportunities provided by new development and improvements in green and other infrastructure to reduce the causes and impacts of flooding, (making as much use as possible of natural flood management techniques as part of an integrated approach to flood risk management)
Southern Water is working across our region to remove surface water from our networks in key areas. Even as we deliver this work, development continues to increase surface water run-off. To be resilient to the evolving impacts of climate change we must plan to ensure that rainwater is separated from wastewater in the design and construction of our communities. For more information on our work, and the root causes of releases from storm overflows, please see –
https://www.southernwater.co.uk/our-region/clean-rivers-and-seas-task-force/pathfinders/
https://www.southernwater.co.uk/our-performance/storm-overflows/storm-overflow-task-force
In terms of community resilience to the impacts of climate change into the future, better rainwater management through SuDS is the preferred approach. Retrofitting sustainable drainage solutions can be challenging. By showing the way with new development we can reduce the implementation costs of these measures whilst securing truly sustainable development.