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Jean-Yves Gilg

Editor, Solicitors Journal

Sustainable drainage: Important new guidance for lawyers

Sustainable drainage: Important new guidance for lawyers


Stuart Pearce examines new drainage guidance and policy that changes the advice lawyers should give to their clients

New guidance and policy on sustainable drainage systems (SuDS) is challenging commercial property and planning lawyers to rethink how we can develop and live alongside increasing environmental risks such as flooding.

Population growth is driving housing demand at unprecedented levels. While one challenge is in freeing up planning rules to accelerate approvals and get building, site suitability is critical.

Climate change is providing the context
for sustainable development into the future. Introducing impermeable surfaces such as roads, pavements, and roofs in a new development increases the amount of surface water flowing into drains and sewers. This adds to the risk and severity of flooding. The extreme events of last winter in Cumbria and Yorkshire demonstrate how susceptible river systems are to sudden downpours. Much of the existing sewer network is unable to cope with an increase in surface water runoff due to its condition and capacity. Many sewers are susceptible to blockages, flooding homes and businesses with huge financial implications.

Policy shifts

In recognition of these risks, new SuDS policy requirements were published in April 2015. These requirements have built upon the Floods and Water Management Act 2010, requiring developers and landowners to consider the suitability of the site for more SuDS.

The National Planning Policy Framework has been updated, requiring new developments in areas at risk of flooding to give priority to the use of SuDS and demonstrate that the proposed development would not increase flood risk to third parties. Local authorities continue to implement stricter planning and referral controls, ruling in favour of SuDS on suitable sites.

Building regulations have also been revised, so that developers are required to consider infiltration to ground or to a surface water feature where conditions permit, in preference to discharging to sewers. Planners are now favouring developments including SuDS, which reduce the volume and slow the rate of surface water runoff.

The Local Authority SuDS Office Organisation (LASOO) was established after 6 April 2015. It is a professional association of local authority officers with involvement in SuDS. LASOO is the owner and writer of the guidance, which sits alongside the non-statutory technical standards for SuDS.

In the guidance, the organisation advises:
'It is highly recommended that pre-application discussions take place before submitting an application to the local planning authority. Ideally, these discussions should start at the land acquisition due diligence stage and continue as part of the pre-planning application process.'

Drainage guidance

Important new guidance specifically for commercial property, environmental, and planning lawyers has been published this month. The guidance outlines solicitors' duty of care when dealing with drainage matters for their property clients.

The author, John H Bates, drainage barrister at
Old Square Chambers, explicitly advises: 'There is a presumption in favour of SuDS for all new developments. SuDS are the preferred approach to managing surface water runoff. Lawyers should commission a pre-application SuDS report to ascertain whether SuDS are appropriate or not, because this has important legal repercussions for your client.'The highly respected barrister and author of Water and Drainage Law is clear that planning authorities are now following a 'drainage hierarchy' where SuDS are the priority where it is practicable
to do so. This is driven by an understanding of the drainage conditions on site, i.e. the ability of a site to drain, and being in a position to respond to the local planning authority as part of the project design from an early stage.

There are important economic reasons for verifying site conditions for SuDS. Aside from satisfying the requirements of the local planning authority, it ensures that the client is clearer about the need to accommodate SuDS in terms of site selection,
design, costs, and future maintenance liabilities.

Incorporating SuDS within the development design will have an impact on the economic feasibility of some sites, so understanding this early is important. However, SuDS shouldn't be seen as a restriction to development and can prove attractive to buyers through improved community amenity.

Lawyers also need to be mindful that the appropriateness of the SuDS on site may give
rise to wider issues of how the system would be maintained in the longer term, and what easements and access rights need to be determined. You already undertake CON29DW water and drainage enquiries of water companies in property transactions to ascertain whether foul and surface water drains from the property and connects to the public sewer. If it does not, your client, the buyer, will have to pay to maintain drains and sewers and may have to bring them up to adoption standards if the water company wishes to adopt them.

However, traditional water and drainage searches do not address the impact of SuDS, which are designed so that they only drain into surface water or combined public sewers as a last resort.

What are SuDS?

SuDS are designed to replicate the natural drainage from a site (pre-development) to mitigate flood risk both on and off site. They provide areas for water storage and drainage as close as possible to where the rain fell, providing a valuable water resource as well as reducing flood risk. As a result, far less surface water is discharged into traditional sewers, taking pressure off existing drains and river systems.

SuDS systems typically perform the following functions: rainwater harvesting, pervious surfacing, infiltration, conveyance, storage, and treatment of water. A combination of these elements is used, sometimes in sequence, to slow surface runoff and encourage local drainage into suitable soil.

SuDS can also make communities more resilient to flood risk, significantly improve the quality of water leaving a site, and enhance the biodiversity of a local area. They do not need energy or pumping and reduce the demand on existing traditional sewers and downstream water treatment. They provide attractive public open space, improve the quality of life, and create better communities.

Since April 2015 local authorities are increasingly intervening to implement SuDS schemes, especially for known flood-risk areas or where soil conditions are most suitable for SuDS. We see an accelerating change to SuDS guidance and a greater focus on signing off on SuDS through the planning process. Identifying whether or not your site is suitable for SuDS is therefore the first essential step in taking these drainage matters into account.

The good news for lawyers and their developer clients is that help is at hand to navigate through this, with a range of resources as part of site due diligence.

SuDS suitability

Understanding the site drainage conditions
and options for SuDS is therefore essential for developers and landowners ahead of submitting
a planning application at the pre-planning stage or to address a planning condition prior to permission being granted.

Commercial property, planning, and environmental lawyers can verify site suitability
for SuDS to clarify drainage requirements and compliance for their client.

SuDSmart reports from GeoSmart Information can be used to support applications and verify suitable conditions for infiltration drainage on site. They can also identify whether or not your site is suitable for SuDS as part of pre-acquisition due diligence.

For more stringent local authorities or more complex site requirements, we can provide alternative options and preliminary scheme
layouts that meet local authority standards.


Key points of the new drainage guidance note
  • There is a presumption in favour of SuDS on all new developments;
  • Drainage requirements follow a ‘hierarchy’ of approval with planning authorities. Draining runoff to a surface water or combined public sewer is now a last resort;
  • SuDS can take up a significant area of a site and have project cost and long-term maintenance impacts that clients need to be alert to;
  • Lawyers must make reasonable enquiries to determine whether SuDS are an appropriate drainage solution for their client’s site;
  • The appropriateness or otherwise of SuDS may affect the legal advice given in respect of planning conditions, easements, adoption, and maintenance, as well as advice relating to insurance cover; and
  • Lawyers should consult the relevant local authority policies on SuDS and seek independent advice from a specialist data provider as part of the pre-acquisition due diligence phase, and also at the outline and detailed planning stages.


For a copy of the SuDS guidance for property professionals and to enquire about SuDS suitability reports for your site, visit, email, or call us on
01743 276 150. SJ


Stuart Pearce is managing director at GeoSmart Information

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