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Guildford Borough Council

Submission Local Plan: Strategy and Sites - Main Modifications

Submission Local Plan: Strategy and Sites - Main Modifications - Part 1: Policies

Policy P4: Flooding, flood risk and groundwater protection zones


4.3.36 Local Planning Authorities, alongside partner organisations, have an increasingly important role to play in protecting communities from flooding and mitigating flood risk. Surrey County Council is the Lead Local Flood Authority in Surrey and has a lead role in managing flood risk from surface water, groundwater and ordinary watercourses in the county. To fulfil its statutory obligations under the Flood and Water Management Act (2010) and contribute to the achievement of sustainable development, the County Council is required to produce a Local Flood Risk Management Strategy and engage with Risk Management Authorities, including Guildford Borough Council, the Environment Agency and Thames Water, with regard to flood risk management.

4.3.37 The River Wey and various other watercourses pass through the borough and have contributed to localised flood events in the recent past, including within Guildford town centre. Nationally, flood events have become increasingly frequent and severe. Such trends are likely to continue within the borough and elsewhere, increasing as a result of climate change. The NPPF requires Local Planning Authorities to take account of climate change, including factors such as flood risk, through the preparation of their Local Plans. New development should be carefully planned to ensure that vulnerability to the range of impacts associated with climate change is not increased.

4.3.38 Detailed flood risk modelling has not been undertaken in all parts of the borough. However, the main areas expected to be at risk of flooding during and beyond the plan period are identified within the Council's Level 1 Strategic Flood Risk Assessment (SFRA) and the Environment Agency's flood risk maps. The Level 1 SFRA highlights the areas at risk of fluvial, groundwater, surface water and sewer flooding and flooding caused by artificial sources. The document also identifies the borough's functional floodplain (known as flood zone 3b), which consists of land considered to be at high risk of flooding. National Planning Practice Guidance suggests that flood zone 3b should form a place for water to flow or be stored in times of flood and be safeguarded from development except for essential infrastructure (as defined in the NPPG).

4.3.39 The functional floodplain (flood zone 3b) in Guildford has historically undergone moderate levels of development. To reflect its existing state, the Level 1 SFRA differentiates between the borough's 'developed' and 'undeveloped' functional floodplain. 'Developed' functional floodplain constitutes the footprint of existing buildings located within the identified functional floodplain. Land in undeveloped flood zone 3b forms important flow routes. Any changes to these flow routes should be considered as part of a Flood Risk Assessment.

4.3.40 In accordance with national planning practice guidance, the Level 1 SFRA has been used to guide development towards areas at the lowest risk of flooding and identify areas unsuitable for development. However, the document concludes that land outside the area of flood risk is not capable of accommodating all of the borough's identified development needs. A Level 2 SFRA has therefore also been produced and will help the Council apply the exception test (as described in the NPPG) as necessary to development proposals in areas at risk of flooding.

4.3.41 The Level 1 and Level 2 SFRAs form an important part of our evidence base. The documents will help ensure that development is guided towards the safest and most sustainable locations in the borough. The Guildford Surface Water Management Plan and Ash Surface Water Study are also relevant in mitigating flood risk in the borough. The documents identify hotspot areas at risk of surface water flooding and appropriate measures for alleviating risk.

4.3.42 Water quality and groundwater protection are also significant issues in the borough. Approximately thirty percent of the Council's administrative area is located on principal aquifers[19] whilst 14 Source Protection Zones (SPZs) are located in the borough. The Environment Agency defines SPZs as groundwater sources, including wells, boreholes and springs, used for public drinking water supply[20]. To protect these sources of drinking water, several restrictions will apply to the type of development permitted within the SPZs.

POLICY P4: Flooding, flood risk and groundwater protection zones

(1) Flood zones in the borough of Guildford are defined based on definitions contained within national planning practice guidance and the Council's Strategic Flood Risk Assessment (Level 1).

(2) Development in areas at medium or high risk of flooding, as identified on the latest Environment Agency flood risk maps and the Council's Strategic Flood Risk Assessment, including the 'developed' flood zone 3b (functional floodplain), will be permitted provided that:

(a) the vulnerability of the proposed use is appropriate for the level of flood risk on the site

(b) the proposal passes the sequential and exception test (where required) as outlined in the NPPF and Government guidance

(c) a site-specific flood risk assessment demonstrates that the development, including the access and egress, will be safe for its lifetime, taking into account climate change, without increasing flooding elsewhere, and where possible, will reduce flood risk overall

(d) the scheme incorporates flood protection, flood resilience and resistance measures appropriate to the character and biodiversity of the area and the specific requirements of the site

(e) when relevant, appropriate flood warning and evacuation plans are in place and approved and

(f) site drainage systems are appropriately designed, taking account of storm events and flood risk of up to 1 in 100 year chance with an appropriate allowance for climate change.

(3) Development proposals in the 'developed' flood zone 3b will also only be approved where the footprint of the proposed building(s) is not greater than that of the existing building(s) and there will be no increase in development vulnerability. Proposals within these areas should facilitate greater floodwater storage.

(4) With the exception of the provision of essential infrastructure, 'undeveloped' flood zone 3b will be safeguarded for flood management purposes.

(5) All development proposals are required to demonstrate that land drainage will be adequate and that they will not result in an increase in surface water run-off. Proposals should have regard to appropriate mitigation measures identified in the Guildford Surface Water Management Plan or Ash Surface Water Study. Priority will be given to incorporating SuDs (Sustainable Drainage Systems) to manage surface water drainage, unless it can be demonstrated that they are not appropriate. Where SuDs are provided, arrangements must be put in place for their management and maintenance over their full lifetime.

(6) Development within Groundwater Source Protection Zones and Principal Aquifers will only be permitted provided that it has no adverse impact on the quality of the groundwater resource and it does not put at risk the ability to maintain a public water supply.


Reasoned justification

4.3.43 To minimise the risk created to people and property from new development and the impacts of climate change, the NPPF instructs Local Planning Authorities to direct development towards areas at the lowest risk of flooding. The Level 1 SFRA has informed the Site Allocations contained within the Local Plan and will be used in the determination of planning applications on unallocated sites. Proposals for development in areas at risk of flooding will be refused if other suitable sites are reasonably available in areas at lower risk. Where a windfall site is promoted, the proposal must also pass the sequential and exception test (where required) and demonstrate to be preferential to those sites already identified as contributing towards development supply.

4.3.44 Within each flood zone new development should be directed to areas of lowest risk first and, following this, to areas suited to the vulnerability of the proposed use. Land-uses considered to be most vulnerable to flooding must be located in areas of lowest flood risk first unless it can be shown that there are overriding reasons to prefer a different location. NPPG will be referred to when assessing the vulnerability of a land use to flood risk. Its definition of 'essential infrastructure' will also be utilised in assessing planning applications in the undeveloped functional floodplain.

4.3.45 For development proposed in areas of greater flood risk (flood zone two or three) and where it is proven through the sequential test that there is no reasonable possibility of locating the development on a site at lower risk of flooding, the Council may request the applicant to demonstrate how their proposal meets the exceptions test. In such instance, applicants will be required to explain how the benefits provided to the community from the proposal outweigh the flood risk associated with the development. Applicants will also be required to submit a site-specific flood risk assessment that explains how the development will be safe to its users and occupiers throughout its life course.

4.3.46 Where there is a proven need for development in areas at risk of flooding, proposals will only be granted permission if they can demonstrate that safe access and egress is provided. In assessing such applications, the Council will refer to guidance provided by the Environment Agency and other relevant parties. Any development proposed within areas of flood risk will require flood management and mitigation measures and should demonstrate that the development is safe from flooding (including the anticipated impacts of climate change) for the duration of its intended lifetime.

4.3.47 Flood Risk Assessments will be required to support planning applications in accordance with the size and location criteria specified in the NPPF and NPPG. Flood Risk Assessments prepared for individual sites should consider flood risk, surface water run-off issues and the potential for sustainable drainage systems to minimise flood risk. Proposals for development in areas at, or potentially at, risk of groundwater flooding will also be required to submit an assessment of groundwater flood risk.

4.3.48 Sustainable Drainage Systems (SuDS) should be provided on all new development unless it can be demonstrated that such measures are inappropriate and suitable alterative drainage mechanisms are proposed. Drainage systems higher in the SuDS hierarchy, as defined by NPPG, will be favoured. However, to ensure effective use over their life course, the Council will require appropriate funding to implement management and maintenance requirements. Applicants should also demonstrate that they have taken into account relevant recommendations of the Guildford Surface Water Management Plan or Ash Surface Water Study.

4.3.49 The water supply in Guildford is a precious resource and it is imperative that it is safeguarded from harmful development. National policy and guidance fully support this stance. The European Union's Water Framework Directive has been produced to deliver a better water environment and the Council, along with other key partners, will play a role in meeting its objectives by carefully planning development so that it does not reduce the quality of, or place pressure on, the water environment. Proposals for polluting industries, cemeteries and other similar uses are unlikely to be appropriate in the borough's identified Source Protection Zones.


Key Evidence

  • Local Flood Risk Management Strategy (Surrey County Council, 2014)
  • Level 1 Strategic Flood Risk Assessment (Guildford Borough Council, 2016)
  • Level 2 Strategic Flood Risk Assessment (Guildford Borough Council, 2016)
  • Guildford Surface Water Management Plan (Guildford Borough Council, 2014)
  • Ash Surface Water Study (Guildford Borough Council, 2014)


Monitoring Indicators



Data source

Number of planning decisions, including appeals, granting permission not in accordance with Policy P4 applications permitted for highly vulnerable uses in flood risk zone three

Percentage of appeals allowed for applications refused on flood risk grounds

No planning permissions that are not in accordance with Policy P4 in flood zone 3b or 3a for highly vulnerable uses

Reduction in percentage of appeals allowed

Planning applications permissions and appeals

Planning appeals




[19] Guildford Local Plan Evidence Base Scrutiny Forum (4 March 2014)

[20] For the most up-to-date information on groundwater sources, see the Environment Agency’s protection position statements: