- A comprehensive guidance note on what is required in a drainage strategy can be provided by the Lead Local Flood Authority (LLFA).
- Development must be in compliance with the current Stockport Local Flood Risk Management Strategy (LFRMS) and contribute positively toward delivering its aims and objectives.
- For sites in reservoir flood locations, applications may be required to undertake an assessment in accordance with advice in the national planning practice guidance, and the assessment should be agreed with the reservoir owner and operator. For sewers, the consultation must confirm if there are any sewer surcharge levels at the point of connection that could influence site design, whether there is an incident of sewer flooding at, or in the vicinity of, the proposed development site; and if sewer modelling data indicates that existing sewers that pass through or near to the site present a modelling risk of sewer flooding. Applicants must not assume that changes in levels or that changes to the public sewer (including diversion) will be acceptable as such proposals could increase/displace flood risk.
- Through the implementation of the Flood and Water Management Act 2010 SuDS are intended to be mandatory for most development throughout England and Wales – see paragraph 7 of Schedule 3.
- The NPPF emphasises that plans should manage flood risk to people and property by safeguarding land from development that is required or likely to be required for current or future flood management. In terms of ‘making effective use of land’, the NPPF states that planning policies and decisions should recognise that some undeveloped land can perform many functions, such as for ‘flood risk mitigation’.
- In areas with a high percentage of impermeable surfaces, the rain that might have soaked into the soil disappears rapidly into gullies and drains so that a short sharp downpour can cause serious flooding problems. Car parks, roads and roofs all serve to speed up the rate of rainfall run-off and increase the risk of flash flooding. Sustainable Drainage Systems (SuDS) should therefore be designed to manage surface water drainage in and around properties and other developments so that it mimics natural (from undeveloped land) run-off rates and thereby slows down or holds back water run-off.
- All SuDS must follow the SuDS hierarchy, prioritising infiltration where feasible before discharge to watercourses or sewers. SuDS should deliver multiple benefits, including water quality improvement, biodiversity enhancement, and amenity value. Properly designed, in addition to helping to avoid flooding, SuDS can help to improve water quality and also improve local amenity, environmental quality and biodiversity, remove pollutants from surface water run-off, form part of green infrastructure networks and reduce the heat island effect. The best SuDS can offer a wide range of solutions, amenity and habitats that are perfect for water management. A well designed SuDS system will often incorporate rain gardens, green roofs, temporary wetlands and a range of other landscape features.
- SuDS design quality will be expected to conform with the National Standards for SuDS 2025. All changes to scheme designs made during the planning process or