Draft Thanet Local Plan - 2031 - Pre-Submission Publication, Regulation 19

Surface Water Management

15.6 Management of surface water is important in terms of reducing the risk of pollutants draining into the groundwater and bathing waters, and reducing the risk of surface water flooding.

15.7 The Thanet Surface Water Management Plan (SWMP) 2013 assessed historic flooding incidents, and identified the causes of this flooding as surface water, sewer, tidal or blocked drains or gullies. SWMPs identify areas which may be vulnerable to surface water flooding as a result of flooding occurring elsewhere (eg excessive drainage into a site from flooding occurring further along a watercourse). An Action Plan has been developed which identifies a range of recommended actions for the reduction of flood risk across the Thanet area.

15.8 The following actions are identified for the Council, which could be achieved through the planning process:

  • Ensure all new developments, where possible, consider the use of Sustainable Urban Drainage Systems (SuDs)
  • Ensure new developments do not increase the risk of surcharge of the sewer network within their catchment
  • Promote benefits of rainwater reuse and recycling
  • Support KCC in the use of SuDs in identified areas

15.9 SuDs are designed to control surface water run-off close to where it falls to and mimic natural drainage as closely as possible minimising pollution and the impacts of flooding (NPPG). Surface water runoff in built up areas tends to flow rapidly into the sewer system, which places a burden on the sewerage network and increases flood risk downstream as piped systems have limited capacity. SuDs can slow the rate at which water disperses, thus reducing the risk of flooding.

15.10 SuDs are more sustainable than traditional drainage methods and they provide opportunities to:

  • Reduce the causes and impacts of flooding;
  • Remove pollutants from urban run-off at source
  • Combine water management with green space with benefits for amenity, recreation and wildlife

15.11 The provision of sustainable drainage within new development became a material consideration in planning decisions from April 2015. Kent County Council is the Lead Local Flood Authority (LLFA) for the county and as such they are the statutory consultee in the planning process to oversee the provision of SuDs for major development within the District. The LLFA provides technical advice and guidance on the surface water drainage strategies, designs and maintenance arrangements proposed by developers for any new major development. Kent County Council has prepared a Drainage and Planning Policy Statement (September 2015) containing guidance on how to integrate sustainable drainage systems into the master planning of large and small developments. Developers should consult and refer to this guidance and any future updates, when preparing applications incorporating SuDs schemes. All applications incorporating a SuDs scheme will also need to include details of a robust maintenance scheme to be agreed with the appropriate authority.

15.12 Sustainable Drainage Systems may have both direct and indirect impacts on the historic environment and historic buildings are often more vulnerable than modern buildings to flood damage to their foundations. Kent County Council has produced guidance on 'The Historic Environment and Sustainable Drainage' and they maintain the County Historic Environment Record (HER). When preparing SuDs schemes developers should fully consider the potential impact on the historic environment and ensure that any avoidable damage is mitigated.

15.13 Kent County Council has prepared guidance on the process from application to adoption of SuDs 'Drainage and Planning Policy Statement 2017'. Developers should consult KCC's guidance and any future updates, when preparing applications for SuDs schemes. KCC should be consulted early on in the process and further information is available from http://www.kent.gov.uk/waste-planning-and-land/flooding-and-drainage/sustainable-drainage-systems.

15.14 Infiltration methods are unlikely to be appropriate in some parts of Thanet due to the quality of the groundwater. Groundwater from the chalk rock beneath Thanet is used to supply water for drinking water, agriculture, horticulture and industry. It also feeds the springs that emerge along the coast and near the marshes. The groundwater is extremely vulnerable to contamination as substances (natural substances and man-made chemicals) are able to pass rapidly through the thin soils and the natural fissures (cracks) in the chalk rock to the groundwater below the ground surface. The acceptability and construction details of infiltration devices is not only based on whether the site is in a Groundwater Source Protection Zone, it also depends on whether the ground conditions are suitable (i.e. free from contamination) and if there are adequate unsaturated area to help reduce any discharge. Proposals for infiltration methods within the Groundwater Source Protection Zone should be discussed with the Environment Agency as it may be possible for SuDs to be lined, or for water to be treated prior to infiltration.

15.15 Under the Water Framework Directive (WFD), the Kent Isle of Thanet Groundwater Body has been classified as poor status for the groundwater quality and quantity. The groundwater is impacted by nitrates, pesticides, solvents and hydrocarbons at levels that are of concern.

15.16 The quality of the groundwater also has an impact on Thanet's bathing waters. The Bathing Water Directive which aims to protect public health and the environment from population has been revised and now introduces tighter water quality standards. This was fully implemented in 2015. Thanet has 13 beaches which have been designated as 'Bathing Waters' under the Bathing Water Directive. Thanet received seven European Blue Flag Awards for its beaches in 2015. These are awarded to beaches that have met and maintained a series of stringent environmental, educational, safety and access related criteria. In addition to this Thanet has been awarded three Seaside Awards for Margate Main Sands, Westbrook Bay and Viking Bay, which rewards beaches in England that achieve the highest standards of beach management. There is also 1 shellfish water designated under the EU Shellfish Waters Directive.

15.17 Walpole Bay has previously failed to meet current EC mandatory bathing water standards and is therefore considered to be at significant risk of not meeting the revised Bathing Water Regulations.

15.18 Bathing waters can be nominated for designation or delisting in the annual DEFRA review. The quality of bathing water quality can be affected by pollution that arises from a variety of sources and the amount of pollution from individual sources may be small but the combined effect can be significant. Diffuse pollution, from agricultural or other sources, can run off land or percolate through it in to rivers which drain into the sea.

15.19 The following factors could contribute to poor bathing water quality in Thanet:

  • Pollution from sewage - bacteria from sewage can enter our waters as a result of system failures or overflows or directly from sewage works.
  • Water draining from farms and farmland - manure from livestock or poorly stored slurry or poor practices in the application of manure on to land can wash into rivers and streams resulting in faecal material entering the sea.
  • Animals and birds on or near beaches - dog, bird and other animal faeces can affect bathing water as they often contain high levels of bacteria (much higher than treated human waste).
  • Water draining from populated areas - water draining from urban areas following heavy rain can contain pollution from a variety of sources, including animal and bird faeces or incorrect connections of waste water from houses and businesses into surface water drainage
  • Domestic sewage - misconnected drains and poorly located and maintained septic tanks can pollute surface water systems.

15.20 The loss of blue flags or the failure of any of Thanet's beaches to meet the requirements of the revised Bathing Water regulations or for Shellfish water failure could have knock-on implications on perception of water quality at neighbouring beaches as well as the local economy and tourist and fishing industry. To ensure development does not negatively impact bathing and shellfish water quality it is important to ensure drainage infrastructure is adequate i.e. sewer capacity is available (or financially viable to increase) and surface water drainage is managed. The following policy seeks to ensure surface water run-off is managed appropriately.

Policy CC02 - Surface Water Management

New development will be expected to manage surface water resulting from the development using sustainable drainage systems (SuDs) wherever possible. SuDs design, together with a robust long term maintenance plan should be considered as an integral part of the master planning and design process for new development. Developers should seek and refer to guidance produced by the Lead Local Flood Authority (LLFA) when submitting a planning application for any major development. Approval for the design and long term maintenance of SuDs will be required prior to development being permitted.

When preparing SuDs schemes developers should fully consider the potential impact on the historic environment and ensure that any damage is mitigated. Proposals for SuDs at sites within the Groundwater Source Protection Zone as shown on the Policies Map, or sites near the Groundwater Source Protection Zone, must demonstrate that the methods used will not cause detriment to the quality of the groundwater.

Sites identified as a Tidally Sensitive Area (as identified in surface water management plans) will need to incorporate Sustainable Drainage Methods and a maintenance schedule where appropriate, at the design stage of a planning application, and a Flood Risk Assessment will be required before planning permission can be granted.