Increases in urban land cover can lead to higher instances of flash flooding after heavy rainfall. Since the 6th April 2015 it is now a legal requirement in English law for all developments of 10 or more units to analyse the potential and use Sustainable urban Drainage Systems (SuDS) to manage run-off, unless it can be demonstrated as being inappropriate.
A Sustainable urban Drainage System is intended to reduce the potential impacts which a given development will have on surface water drainage discharges (run-off rates). A surface water drainage strategy is a report which seeks to meet the legal requirement through an investigation of how surface water will affect the site and the areas surrounding it and providing a suitable potential drainage strategy to mitigate the effects of the development. The report will establish how water behaves on the site, and determines the run-off rate, flow pathways and infiltration potential.
The new legislation applies to the following types of developments:
- 10+ Residential dwellings (this is not the number of structures, but rather a count of the dwellings (including flats);
- 10+ Commercial units;
- 10+ Mixed-use units, and;
- All major commercial developments.
These changes do not affect the National Planning Policy Framework but instead are an addition to the existing requirements. Furthermore, the UK government has now made Local Planning Authorities responsible for ensuring that developments comply with the new policy.
What could this mean for you?
It is likely that your local planning authority will begin to request ‘Surface Water Drainage Strategies’ to address the need for SuDS as part of the planning process for these larger developments. Ambiental can assist planning applications in a variety of ways, ranging from undertaking calculations which establish the changes in surface water run-off which a development will cause, right through to designing a suitable strategy prescribing measures which mitigate the impacts of the development.
Need more information about a Surface Water Drainage Strategy?
Ambiental has created a brochure explaining what a surface water drainage strategy is and how the process works which can be downloaded by following the hyperlink here. Further information on drainage can be found on the Ambiental website here.
Want to read the governments statement regarding the new policy?
This can be found by clicking here.
If you would like to discuss this new policy and how it may affect your developments please don’t hesitate to contact us on 01273 704 441 or email us.
The above image shows the proposed drainage strategy overlain the development site, allowing the client to effectively visualise how the drainage strategy interacts with the proposed development. This style of plan is included as standard in our Surface Water Drainage Strategy report.
An interceptor pond is one of a range of solutions for capturing surface water from a site and storing it before it is released to a watercourse or directed onwards to receive additional treatment.
A sedum green roof design can absorb rain water and delay the conveyance of water away from the site. Interception of rainwater by vegetation is an effective way of mitigating the increases in surface water run-off caused by a development.
Filed in: Flood modelling