Policy information sourced from Harpenden Neighbourhood Plan
ESD18 – Flood Risk
Proposals must incorporate a sustainable and integrated approach to the management of flood risk, surface water (including run off) and foul drainage. These proposals should be robust to the expected impacts of climate change.
Developments over one hectare or all developments in Flood Zone 2 or 3 must be supported by a Flood Risk Assessment.
All development involving the loss of permeable surfaces, loss of trees, loss of soft landscaping or loss of any other feature that reduces flood risk is required to use appropriate mitigation measures to prevent an increase in flood risk within the site or elsewhere. This should be proportionate to the scale of the proposal, with small interventions (such as planting or use of impermeable surfaces) acceptable for minor developments in areas of low flood risk.
Sustainable Drainage Systems (SuDS) should be used proportionately to mitigate any predicted increase in flood risk. These may include:
- Planting, particularly trees.
- Introduction of permeable driveways, parking or other ‘hardstanding’ areas.
- Rainwater water harvesting and storage features (including butts).
- Green roofs.
- Attenuation tanks.
- Soakaways.
- Attenuation ponds.
SuDS must be designed as an integral part of the green infrastructure and street network. The system should effectively mitigate any adverse effects from surface water run-off and flooding on people, property and the ecological value of the local environment. A surface water sewer should be seen as a last resort and no surface water will be permitted to enter the public foul sewage network.
Major developments must provide a SuDS Strategy and drawings showing all SuDS features. This must be supported with calculations showing how surface water flood risk will not increase.
For more information please see the Neighbourhood Plan