Is your site water tight?

Regulation of the water environment has become increasingly topical and tighter. With enhanced knowledge of the potential impacts of climate change, the design standards for both flood risk and surface water drainage have altered to keep pace. New requirements have emerged too, such as the requirement for Nutrient Management Plans, principally relating to foul drainage. 

Considering these issues upfront and designing in mitigation from the outset can reduce time and costs associated with altering masterplans to retrofit mitigation. To help you avoid getting caught out on new schemes, we’ve included some of our top tips and things to avoid below.

✔ Top tips

  • Due diligence – undertake a flood risk and drainage constraints appraisal before buying or optioning a potential development site
  • Establish early on the flood risk design standard (including appropriate allowance for climate change), so that the developable area and other mitigation requirements can be factored into the scheme
  • Seek confirmation from the LPA or an appropriate consultant as to whether nutrient neutrality must be achieved
  • Investigate potential surface water and foul drainage discharge connections for the site early on to avoid impacting programme timeframes
  • Anticipate that above ground Sustainable urban drainage system (SuDS) techniques such as ponds and swales will need to be included on greenfield sites and leave space (suggest approx. 10% of the site) within the masterplan for this
  • Maximise opportunities for more preferable SuDS techniques to be incorporated (see flowchart below) and prepare robust justification for why the preferred techniques cannot be included, where necessary
  • Engage with the EA, local authorities and other statutory consultees, where appropriate, as early as possible to determine requirements and agree mitigation strategies
  • Work undertaken at pre-submission stage can often reduce the number of associated planning conditions, reducing cost and programme risk post determination

× Things to avoid

  • Don’t get too far into the design process before considering flood risk and drainage constraints – this can affect viability as well as the outcome of the application process
  • Don’t assume that because a site is in Flood Zone 1 it will not require consideration of flood risk - there may still be risks which require investigation and mitigation
  • Don’t expect local planning authorities to identify all flood risk or drainage concerns at pre-application stage – they will probably focus more on the principle of the proposed development
  • Don’t make assumptions based on projects from a few years ago. What was an acceptable mitigation strategy previously may no longer meet current policy requirements
  • Beware the power of lived experience – flooding events can alter local authorities’ perception and willingness to accept safe refuge as sole emergency management protocol

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