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Islington Council Planning Guidance

London Borough of Islington Council planning policy for sustainable drainage reports, flood risk assessments and contaminated land risk assessment are driven by environmental conditions and the local authority policy.
Guidance for architects, and developers on flood risk, drainage and phase 1 contaminated land reports is summarised below with links to the key summary documents.

Islington Council Contaminated Land

The developer and their environmental consultant, such as GeoSmart, will need to assess the potential risks from contamination on the basis of the proposed use and local circumstances.  This should normally be done before the formal planning permission is given for the development.  However, in some cases, permission can be granted subject to a condition, which will require developers to investigate whether there is any land contamination and, if necessary, devise a strategy to deal with it.

Where a developer is proposing to develop land that is suspected of being contaminated, it is advisable to contact the Contaminated Land Officer before submitting the planning application.  It is useful to do this as the Council may have additional information that you are unaware of and may also be able to answer any particular questions that you have.

Procedure for dealing with land potentially affected by contamination:

  • Step 1 – the desktop study. This should establish former uses of the site and adjacent buildings, include a site walkover survey, identify contaminants of concern, develop a site-specific conceptual model and compile conclusions and recommendations.
  • Step 2 – detailed site investigation (when necessary). This should include the design of a sampling strategy and samples being taken (based on the conceptual model.) A quantitative risk assessment should be undertaken, comparing results of sampling with appropriate standard and should identify unacceptable risks. If necessary, it should identify appropriate remediation options available.
  • Step 3 – remediation strategy (when necessary). Preferred remedial options should be selected and submitted for approval. Remedial works should be designed and implemented.
  • Step 4 – validation report (where necessary). Following completion of works, developers should compile a validation report to demonstrate works have been carried out according to remediation strategy, and detail any changes that occurred.

Site Walkover Reconnaissance

Islington Council request a site walkover is undertaken as part of the desktop study.

Guidance for Contaminated Land

Islington Council


Islington Council Flood Risk Assessment

The entirety of LBI is located in Flood Zone 1 (low risk) considered as land having a less than 1 in 1,000 chance of river flooding each year (0.1% AEP).

Overland flow and surface water flooding typically arise following periods of intense rainfall, often of short duration, that is unable to soak into the ground or enter drainage systems. This occurs most commonly in urban areas where water is unable to enter the ground due to the presence of impermeable surfaces. There are three Critical Drainage Areas (CDAs) which cover the majority the London Borough of Islington.

Areas of Islington to be susceptible to surface water flooding, include:

  • Caledonian Road (bottom of canal museum),
  • Clerkenwell Road,
  • Jackson Road,
  • Finsbury Park Station – Severn Sisters Road (entrance near the bridge), and,
  • Upper Holloway area.

Within LBI the artificial flood risk sources include:

  • The Regents Canal
  • The New River
  • Maiden Lane Reservoir
  • Claremont Square Reservoir
  • Water Supply Network

Within LBI, the areas which are likely to have the greatest potential for groundwater flooding to occur are generally in the south of the Borough, underlain by permeable superficial deposits These areas include; the eastern boundary with Hackney, from Leconfield Road to the junction of City Road and Tabernacle Street in the south. There are also areas along the western boundary with Camden, from Margery Street along Farringdon Road, to the southern edge of the Borough, and further north around Highbury and Islington station.

The NPPF states that a site specific FRA is required in the following circumstances:

  • Proposals for new developments (including minor developments and change of land use) in Flood Zones 2 and 3.
  • Proposals of 1 hectare or greater located in Flood Zone 1.
  • Proposals of less than 1 hectare in flood zone 1, including a change of use in development type to a more vulnerable class, which could be affected by sources of flooding other than rivers and the sea.
  • Proposals in areas which are within Flood Zone 1 which have critical drainage problems as notified by the Environment Agency, for example surface water drains.

As LBI is located entirely within Flood Zone 1, advice relating to Flood Zone 2 and 3 is not relevant here.

Islington is faced by a number of pressures which could influence flood risk in the future, both adversely and beneficially, these include:

  • Climate change leading to more intense periods of rainfall, increasing the frequency of large-scale flooding and the chances of flooding occurring where it has not been experienced before;
  • Heightened sewer levels preventing surface water from draining;
  • Population increase leading to increased demand for development and key services;
  • Pressure for new development in areas at risk of flooding or changes in land use which increase risk elsewhere;
  • Deterioration of structures or features that currently protect us from flooding and thus require maintenance or replacement;
  • Lack of maintenance or replacement of said structure or features of the existing strategic drainage network;
  • Public sector cuts leading to reduced maintenance activities and reduced central government funding for flood alleviation schemes; and
  • More stringent building regulations and new developments which can contribute to reducing flood risk.

Sites located in Local Flood Risk Zones (LFRZs) will be required to submit a Flood Risk Assessment (FRA) to assess the risk of flooding, particularly surface water flooding, taking climate change projections into account. Where the FRA indicates that an additional volume of run-off must be stored above and beyond the amount calculated based on the method above, this must be provided on site.

Level 1 Strategic Flood Risk Assessment

Islington Council


Islington Council Sustainable Drainage SuDs

Development in Islington almost always takes place on previously developed land with an existing connection to the combined sewer. Most developments in the borough are also of very high densities with little outdoor space. In these situations, flow routes have been destroyed by previously developed urban features and natural drainage may be difficult to replicate. However, despite the challenges presented by this context, there are a number of opportunities to incorporate SUDS within new or refurbished developments in a way which meet design standards and provide a range of benefits for the development and the wider environment and local area.

Applications for major developments creating new floorspace and major Changes of Use that are likely to result in an intensification of water use are required to include details to demonstrate that SUDS have been incorporated and meet the following design standards:

i) Quantity: schemes must be designed to reduce flows to a ‘greenfield rate’ of run-off (8 litres/second/hectare for Islington), where feasible. The volume of run-off that must be stored on site should be calculated based on the nationally agreed return period value of a 1 in 100 years flood plus a 30%allowance for climate change for the worst storm duration. Where it is demonstrated that a greenfield run-off rate is not feasible, runoff rates should be minimised as far as possible. The maximum permitted runoff rate will be 50 litres/second/hectare.

ii) Quality: the design must follow the SUDS ‘management train’, maximise source control, provide the relevant number of ‘treatment stages’ and identify how the ‘first flush’ will be dealt with.

ii) Amenity and biodiversity: the design must maximise amenity and biodiversity benefits, while ensuring flow and volumes of run-off entering open space are predictable and water at the surface is clean and safe. Schemes should maximise areas of landscaping and/or other permeable surfaces to support this.

Surface Water Drainage Guidance

Islington Council


Islington Council Groundwater Flood Risk

There are superficial deposits in the southern half of Islington comprising of River Terrace Deposits (Figure B, Appendix B). The named formations are Hackney Gravel Member (Sand and Gravel (S&G)), Taplow Gravel Formation (S&G), Alluvium (Clay, Silt, Sand and Gravel), Langley Silt Member (Silt), Boyn Hill Gravel Member (S&G) and Finsbury Gravel Member (S&G). The bedrock geology (Figure C, Appendix B) in the Borough is underlain primarily by Thames Group – clay, silt, sand and gravel.

Please see the SFRA document for more details.

For further advice please contact us