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How does the Council deal with surface water drainage matters during the planning process?

Land drainage guidance note for planning applicants regarding surface water drainage

 Content

1.  Purpose of note

2.  Types of planning application and the approach to be followed

(i)  Residential development

  • Residential Extensions

  • Up to 9 Dwellings

  • Multiple Curtilages

  • Dwellings in the no new soakaway zone

  • Ten or more dwellings

(ii) Non-residential development

  • Non Residential Development

(iii) Exceptions

  • Exceptions

3. Information for Applicants.

(i)  Policy Requirements and the Strategic Flood Risk Assessment

(ii)  Planning Consultations

  • The Environment Agency's Role

  • The Lead Local Flood Authorities Role

  • The Local Planning Authority's role

(iii) Design Criteria

(iv) Connections to watercourses / Surface Water Systems

Appendix One- Definitions

Appendix Two Useful web sites and information

Appendix Three  Applicant Check List

 

 

1.   Purpose of note

To provide advice regarding how the planning requirements applying to surface water drainage issues are normally dealt with, in a manner that reflects Government Policy and Guidance and the resources available within New Forest District Council.

2.  Types of application and the approach to be followed

(i)  Residential development

Residential Extensions

If the proposal is for an extension to a domestic dwelling the design and construction will normally be covered by the Building Control Regulation procedures whether they are provided through the Council or an external provider. This process includes the provision of satisfactory surface water drainage arrangements so normally no planning condition will be imposed.

Up to 9 Dwellings

For a new dwelling or up to nine dwellings (non-major development) a planning condition will normally be imposed as follows:

Before first occupation of the development hereby approved, a surface water sustainable drainage system (SuDS) shall be designed and installed to accommodate the run-off from all impermeable surfaces including roofs, driveways and patio areas on the approved development such that no additional or increased rate of flow of surface water will drain to any water body or adjacent land and that there is capacity in the installed drainage system to contain below ground level the run-off from a 1 in 100 year rainfall event plus 30% on stored volumes as an allowance for climate change as set out in the Technical Guidance on Flood Risk to the National Planning Policy Framework.

Infiltration rates for soakaways are to be based on percolation tests in accordance with BRE 365, CIRIA SuDS manual C753, or a similar approved method. 

In the event that a SuDS compliant design is not reasonably practical, then the design of the drainage system shall follow the hierarchy of preference for different types of surface water drainage system as set out at paragraph 3(3) of Approved Document H of the Building Regulations.

The drainage system shall be designed to remain safe and accessible for the lifetime of the development, taking into account future amenity and maintenance requirements.

Reason: In order to ensure that the drainage arrangements are appropriate and in accordance with Policy CS6 of the Core Strategy for the New Forest District outside the National Park and the New Forest District Council and New Forest National Park Authority Strategic Flood Risk Assessment for Local Development Frameworks.

 Multiple Curtilages

Where there is more than one curtilage and the sustainable surface water system is shared then a maintenance condition will also normally be imposed as follows:

Before first occupation of the development hereby approved the applicant shall have set up a detailed scheme for the future maintenance of the sustainable drainage system, including arrangements of the responsible parties for the maintenance of the sustainable drainage system. The system shall thereafter be retained and maintained in accordance with the scheme. 

Reason: In order to ensure that the drainage arrangements are appropriate and in accordance with Policy CS6 of the Core Strategy for the New Forest District outside the National Park and the New Forest District Council and New Forest National Park Authority Strategic Flood Risk Assessment for Local Development Frameworks.

Dwellings in the Soakaway Restriction Zone (Barton On Sea)

For all new dwellings in the 'Soakaway Restriction Zone' at Barton on Sea (see section 3(iii) below) a planning condition will be imposed as follows:

Before first occupation of the development hereby approved a surface water sustainable system (SuDS) shall be designed and installed to accommodate the run-off from all impermeable surfaces including roofs, driveways and patio areas on the proposed development such that the discharge of surface water to the ground using soakaways or permeable paving is not included in the design and no additional or increased rate of flow of surface water will drain to any water body or adjacent land and that there is capacity in the installed drainage system to contain the run-off from a 1 in 100 year rainfall event plus 30% on stored volumes as an allowance for climate change as set out in the Technical Guidance on Flood Risk to the National Planning Policy Framework.   

In the event that a SuDS compliant design is not reasonably practical, then the design of the drainage system shall follow the hierarchy of preference for different types of surface water drainage system as set out at paragraph 3(3) of Approved Document H of the Building Regulations.

The drainage system shall be designed to remain safe and accessible for the lifetime of the development, taking into account future amenity and maintenance requirements.

Reason: In order to ensure that the drainage arrangements are appropriate and in accordance with Policy CS6 of the Core Strategy for the New Forest District outside the National Park and Policy DM7 of the Local Plan Part 2: Sites and Development Management, New Forest District outside the National Park and the New Forest District Council and New Forest National Park Authority Strategic Flood Risk Assessment for Local Development Frameworks.

Ten or more dwellings

Residential development comprising 10 or more dwellings will be dealt with in a similar manner to that regarding residential development of up to 9 dwellings.  However close liaison with Hampshire County Council as Lead Local Flood Authority will also be required meaning that additional or bespoke conditions may also be imposed.

 

(ii)  Non Residential Development

Non-residential development will be dealt with in a similar manner to residential development, with smaller developments on non-constrained sites being dealt with under the Building Regulations and larger developments being the subject of additional consultation with the Lead Local Flood Authority which may be subject to additional or bespoke conditions.  The exact approach will be determined on an application by application basis.

 

(iii) Exceptions

The information below does not cover developments in Groundwater Source Protection Zones (Lymington and north of Fordingbridge) or developments requiring a Flood Risk Assessment.

In the event that site specific concerns are raised by the public or identified by the Case Officer then a site specific process will be followed where the Case Officer will consult the Council's Drainage Engineer for detailed advice.  An applicant will be advised when this is the case.

 

3. Information for Applicants

The following information is designed to assist in the understanding of the wider framework the Councils Drainage Guidance relates to.

(i) Policy Requirements and the Strategic Flood Risk Assessment

National Planning Policy Framework (NPPF) requirements and flooding

  1. Flood risk is a material planning consideration and relates to all forms of flooding including that from rivers and the coast. It is a very important factor in the planning process particularly in the light of current concerns about climate change and the need for sustainable development.

  2. The aim of national policy guidance is to ensure that flood risk is taken into account at all stages of the planning process, to avoid inappropriate development in areas at risk of flooding, and to direct development away from areas of highest risk and to not increase flood risk elsewhere. The National Planning Policy Framework (NPPF) sets out how to minimise vulnerability and provide resilience to the impacts of climate change. 

  3. A Strategic Flood Risk Assessment for Local Development Frameworks has been produced by New Forest District Council and the New Forest National Park Authority which sets out more specific local details.

    http://www.newforest.gov.uk/article/14770/Strategic-Flood-Risk-Assessment

  4. Flooding of property in the New Forest District has occurred mainly in low lying coastal areas and from the more major watercourses and "Main Rivers". However, flooding of property has also come from other sources such as minor or "ordinary watercourses", overland flows from fields etc., high groundwater levels and from the highway. A planning application could be refused for certain developments within a flood risk area and also if the proposal would lead to increased flood risk. (Main rivers are watercourses defined on a Main River Map which is held by the Environment Agency and any watercourse that is not a Main River is defined as an ordinary watercourse

http://maps.environment-agency.gov.uk/wiyby/wiybyController?x=357683&y=355134&scale=1&layerGroups=default&ep=map&textonly=off&lang=_e&topic=mainrivers

(ii) Planning consultations

The Environment Agency's Role

1.  The Council has a statutory role to consult the Environment Agency on development other than minor development or as defined in the EA Flood Risk Standing Advice, which is carried out on land: within flood zone 2 or 3 or in areas within flood zone 1 which has critical drainage problems as notified by the Environment Agency.

http://maps.environment-agency.gov.uk/wiyby/wiybyController?x=357683.0&y=355134.0&scale=1&layerGroups=default&ep=map&textonly=off&lang=_e&topic=floodmap

2.  For a property in zones 2 & 3 the Council encourages applicants to enter into pre-planning discussion with this Council and the Environment Agency before submitting their planning application. You can do this using the relevant pre-application enquiry form. 

http://www.newforest.gov.uk/article/13716/Am-I-likely-to-get-planning-permission-for-a-scheme-or-project

3.  For a property in zone 1 a Flood Risk Assessment (FRA) may be required depending on the type, number of properties and location of development proposed. Applicants are advised to cover this issue during pre-application advice or e-mail the location, ordnance survey grid reference and outline proposals to Planning at Dev.control@NFDC.gov.uk for general advice on whether a FRA will be required. The Environment Agency, working with Defra and the DCLG has produced an FRA template: https://www.gov.uk/guidance/flood-risk-and-coastal-change#Site-Specific-Flood-Risk-Assessment-checklist-section for developers to help ensure that all necessary elements of the FRA are covered.

Lead Local Flood Authorities Role

4.  The Lead Local Flood Authority (Hampshire County Council) is consulted regarding development that is classified as 'Major Development' in the Town in the Country Planning Statutory instrument 2015 No. 595. This includes sites where the number of dwelling houses is 10 or more or a floor space created by the development is 1000 square metres or more. The act will need to be referred to for a full list of what is described as Major Development. Hampshire County Council is a statutory consultee for surface water drainage on Major Development.

The list of the Lead Local Flood Authorities requirements are available on the website :-

http://www3.hants.gov.uk/flooding/hampshireflooding/drainagesystems/planning-application-guidance.htm

The Local Planning Authority's role

5.  To consider the design of land drainage proposals in the context of landscape and layout designs and ensure that likely drainage proposals do not detract from the ability of areas of public land to fulfil their other functions whether they are as recreational public space, amenity space, streets or courtyards.

To ensure that any potential alterations to normal groundwater conditions within public greenspace do not put existing landscape features or habitats at risk and to consider how proposal's can enhance public greenspace.

To ensure that there is no potential management or maintenance conflict with either of the above and to assist where possible in ensuring a joined up future management approach.

(iii) Design criteria

1.  Under the National Planning Policy Framework all developments should be undertaken in a sustainable manner and under the National Standards for Sustainable Drainage Systems (December 2011) the following destinations must be considered for surface runoff in order of preference:

  • Discharge into the ground
  • Discharge to a surface water body
  • Discharge to a surface water sewer
  • Discharge to a combined sewer

2.  NORMALLY ANY METHOD CHOSEN FOR THE DISPOSAL OF SURFACE WATER WILL NEED TO BE DESIGNED SUCH THAT THERE WILL BE NO ADDITIONAL WATER, ADDITIONAL VOLUME, OR INCREASED RATE OF FLOW OFF-SITE DURING OR ON COMPLETION OF THE PROPOSED CONSTRUCTION FOR ALL STORMS UP TO 1 IN 100 YEARS PLUS CLIMATE CHANGE.

3.  If the ground is permeable and it is not in a "No New Soakaway Zone" or Environment Agency special protection zone then soakaways should be considered before other methods.  These would need to be designed in accordance with BRE365 (latest edition).  Drawings will need to show the soakaway location which is to comply with Building Regulations for location purposes. Soakaway crate manufacturers may help with the design. Important information that is needed to design a soakaway is the infiltration rate and impermeable area to be drained

If the water table is relatively close to the surface then a designed permeable paving system may be appropriate or other method of infiltrating near the ground surface.

4.  If the soakaway is to be located in a Special Protection Zone (SPZ) then the Environment Agency should be consulted. There is a SPZ in north Lymington and North of Fordingbridge. They can be located on the Environment Agency website. Under the groundwater heading.

5. If the existing previously developed site drains to a watercourse or surface water system then this can be continued with the new development but in most cases with a reduced flow rate. If the site was previously a greenfield site then the greenfield site run off must not be exceeded with the new development. If the site was previously developed then wherever possible the greenfield site equivalent should be the proposed flow.

6. Rainwater Harvester Systems can be used but with an overflow to a soakaway or watercourse without exceeding the discharge flows previously noted.  Particular attention should be given to the annual use of harvesting systems with regard to seasons of the year when calculating volumes. Backup measures are often a requirement for these systems so that flooding does not occur.

7. Water Butts can be used in the design providing that they are located where their failure would not lead to a property owner easily connecting to a foul sewer or even a surface water system thereby negating the reason for the water butt installation. The consequences of failure of a water butt should be considered at the design stage.

8. Ponds, wet/dry/infiltration ponds, wetlands, swales, filter drains are some of the Sustainable urban Drainage System (SuDS) methods that can be used if the site is of a sufficient size.  In all cases they can be designed to hold water and reduce outflow, and levels of pollution, from the site.

9.  Reference for all Sustainable Drainage Systems should be made to The SuDS Manual 2015. (CIRIA C753)

10.  If the site is in the coastal area of Barton on Sea as shown in the shaded area on the map below it will be in the "Soakaway Restriction Zone" and new soakaways will not be permitted.
adobe icon Barton on Sea - No Soak away area [74kb]  

See also NFDC Policy DM7: Restrictions on new soakaways

http://www.newforest.gov.uk/media/adobe/i/l/Interim_adoption_text_Section_1and_2.pdf

11. Foul sewers are not designed to deal with large volumes of surface water run-off from roofs and paved areas so connection of surface water to a foul sewer is not usually permitted by the water company. If the applicant has received permission from the water company to connect into the foul system then written evidence would need to be provided with the application.

12.  There are few combined sewers in the New Forest District Council area.

13.  The Water Company will need to be contacted it there is to be a connection to a public surface water sewer or combined sewer. However as most surface water sewers connect to watercourses then the proposed discharge rates are to be no greater than those previously described in this document. Adoption of the proposed system will need to be discussed with the Water Company.

(iv) Connections to watercourses / Surface Water Systems

Watercourses including rivers, ditches, brooks and piped watercourses.

Any work that is likely to affect the flow in a watercourse may require the consent of Hampshire County Council if it is an ordinary watercourse or the consent of the Environment Agency if it is on the main river map.

Contacts

Pipe, culvert or alter any ordinary watercourse, including rivers and ditches.

Hampshire County Council (Tel: 01962 846730).

Please see HCC Website http://www3.hants.gov.uk/flooding/watercourses.htm

 

Create or alter any discharge, which may include pollutants, to a river, watercourse, ditch, pipe or culvert or alter any Main River watercourse, including rivers and ditches.

Environment Agency (Tel 03708 506506)

http://maps.environment-agency.gov.uk/wiyby/wiybyController?x=357683.0&y=355134.0&scale=1&layerGroups=default&ep=
map&textonly=off&lang=_e&topic=floodmap#x=443386&y=101549&lg=1,2,10,&scale=10

A developer can only connect to a watercourse if it is in the applicant's ownership or permission has been agreed with the watercourse owner.

Granting of planning permission does not grant the right of connection.

Appendices

adobe icon Appendix 1 - Soakaways [87kb]

adobe icon Appendix 2 - Useful web sites and information [30kb]

adobe icon Appendix 3 - Applicant checklist for 1-9 dwellings [33kb]

For major applications of 10 dwellings or more or larger commercial schemes, Hampshire County Council, as the Lead Local Flood Authority, require the completion and submission of  their pro forma/checklist

adobe icon Surface Water Management - Developer's Checklist [299kb]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

           

Updated: 16 Oct 2017
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