SUDS: Information

From 15th April 2015 Lead Local Flood Authorities (in our case Bucks County Council) will become a statutory consultee on surface water drainage for major planning applications. Applications determined thereafter will have to ensure that sustainable drainage systems are in place, unless demonstrated to be inappropriate. In order to achieve this, applicant's should include the following information in their submissions. If the information is not included applications may be refused for failure to demonstrate that surface water will be dealt with in an appropriate manner.

Sustainable Urban Drainage Systems Statement (SUDS)

What is it?

A sustainable drainage statement can be included within a Flood Risk Assessment and covers a range of sustainable approaches to surface water drainage management including:

(a) Source control measures including rainwater recycling and drainage

(b) Infiltration devices to allow water to soak into the ground (individual or communal)

(c) Filter strips and swales

(d) Filter drains and porous pavements to allow rainwater to run-off to infiltrate into porous material below ground and provide storage if needed

(e) Basins and ponds to hold excess water after rain and allow controlled discharge to avoid flooding.

When is it required?

When a major development- 10 or more dwellings or equivalent non-residential or mixed development (Article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015) is likely to give rise to a risk of surface water or groundwater flooding.

What is required?

(The following information can be completed on the  Icon for pdf Surface Water Drainage Proforma [244.61KB]

Applications for full planning permission, reserved matters and outline applications where layout is submitted for approval should include the following:

Plans, including;

Technical plans and drawings

  • A detailed site layout at an identified scale with a North point of the proposed drainage system with catchment areas.
  • Long sections and cross sections for the proposed drainage system including impermeable areas.
  • Construction details and details of connections (including flow control devices) to watercourses, sewers, public surface water sewers, highway drains and drainage systems.
  • Landscape planting scheme if proposing vegetated drainage system.

Written and management plans

  • A plan for the management of construction to include; phasing of works, in relation to other parts of the construction, and maintaining the system (including access arrangements, operational characteristics, and energy requirements for constructing and maintaining all proposed drainage systems) and the details of any offsite works required, together with any necessary consents period and any impacts, such as diversions and erosion control.
     
  • A health and safety plan for example in relation to areas of open water and confined space entry. If a health and safety plan is not considered to be relevant then this should be indicated with the reasons why.
  • A maintenance plan setting out how to maintain the full drainage system following construction with details of who is to be responsible for the maintenance.

Surveys, including:

A topographical survey of the site, including cross-sections of any adjacent watercourses for appropriate distance upstream and downstream of discharge point if appropriate.

  • Details of the existing site layout, drainage system and catchment areas,
  • Details of the existing geology and hydrogeology
  • Ground investigations, (including groundwater and contamination), and infiltration tests, where appropriate.
  • Surveys of any existing drainage systems or water bodies to which the SuDS may discharge if these are off the site.

Assessments, including:

  • An assessment demonstrating flooded areas for the 1% (1 in 100) annual exceedance probability storm when system is at capacity and demonstrating flow paths for design for exceedance.
  • Full design calculations and design parameters to demonstrate conformity with the design criteria for the site.
  • Design criteria in relation to/from ground contamination, infiltration tests, ground water assessments and soil stability.
  • Any requirements for temporary drainage features or discharge points during construction.

Evidence or reports including:

  • Confirmation of discharge consent
  • Confirmation of discharge location.
  • Discharge capacity.
  • Agreements with other bodies.

Applications for outline permission where layout is reserved should include the following:

  • A summary providing an overview of the drainage strategy.
  • A map showing topography, surface flow paths, watercourses, natural conveyance/storage/infiltration zones, flood risk mapping (surface water and fluvial) relevant to the proposed development site.
  • A map showing soil types, underlying geology, groundwater bodies, infiltration test locations and constraints (e.g. contamination) relevant to the proposed development site.
  • Description of receptor likely to receive runoff from the site drainage system (water body or sewer) and if discharging to a water body, list the characteristics (including environmental designations) of any groundwater or surface water bodies relevant to the proposed development site.
  • A map showing any existing surface or combined sewers, culverted watercourses, highway drains and/or other impediments/constraints to natural drainage paths relevant to the proposed development site.
  • % permeable/impermeable areas before and after proposed development
  • Runoff rates and volumes
  •  Infiltration test result details and if applicable, infiltration capacities
  • Confirmation of discharge location.

These list are not exhaustive and, depending on site conditions, further information may be required during the consideration of an application. These details should be confirmed with the Flood Management Team, Buckinghamshire County Council, County Hall, Aylesbury, HP20 1UY: 01296 382653 ; sab@buckscc.gov.uk in advance of any application.

High level constraints and calculations should be presented in a uniform fashion with a one page summary dedicated to giving and overview of the drainage strategy.

  • A map showing topography, surface flow paths, watercourses, natural conveyance/storage/infiltration zones, flood risk mapping (surface water and fluvial) relevant to the proposed development site.
  • A map showing soil types, underlying geology, groundwater bodies, infiltration test locations and constraints (e.g. contamination) relevant to the proposed development site.
  • Description of receptors likely to receive runoff from the site drainage system (water body or sewer) and if discharging to a water body, list the characteristics (including environmental designations) of any groundwater or surface water bodies relevant to the proposed development site.
  • A map showing any existing surface or combined sewers, culverted watercourses, highway drains and/or other impediments/constraints to natural drainage paths relevant to the proposed development site.
  • % permeable/impermeable areas before and after proposed development
  • Runoff rates and volumes
  • Infiltration test result details and if applicable, infiltration capacities

Useful information sources

Technical Guidance to the National Planning Policy Framework

There are a number of design guides, such as The SuDS Manual (CIRA C697). Further design guidance can be found on the Susdrain website.