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Do I need a Surface Water Drainage Strategy? 

A Surface Water Drainage Strategy is required to accompany a planning application when:

  • A development comprises 10 or more dwellings

  • A development site has a total area greater than 1 ha

  • The floor space to be created by a development is over 1000m2

  • A development comprises less than 10 dwellings but is located within :

    • an area identified at risk of flooding (including surface water), and / or

    • an area identified as having a critical drainage problem

  • proposes to increase the impermeable area at a site and the Local Planning Authority are concerned about the cumulative impacts of development in the area.

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The specific requirements for SuDS vary based on geographic location and corresponding Local Policy Guidance. However, it is becoming increasingly common for Local Planning Authorities and Lead Local Flood Authorities to require surface water drainage information from developers at the early stages of the planning process. 

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Our consultants have completed hundreds of Surface Water Drainage Strategies, for both commercial and residential developments, throughout England helping developers achieve planning approval. Our track record demonstrates our grasp on understanding what each Lead Local Flood Authority requires. If you have a development site which you need assistance with, do not hesitate to get in touch with one of our dedicated team who would be happy to discuss your development in more detail. 

Do I need a Surface Water Drainge Strategy

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Green Roofs

What is a Surface Water Drainage Strategy?

A Surface Water Drainage Strategy is a report which outlines how surface water runoff generated within a site boundary will be managed post development in accordance with the NPPF (England), TAN15 (Wales) and Local Planning Policy Guidance.  

 

A Surface Water Drainage Strategy includes an assessment of site characteristics and any features within the surrounding area that could influence how water landing on a development site behaves. 

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Typical considerations include underlying ground conditions, previous land uses, proximity to the nearest watercourse and surface water sewer, the location of any Tree Preservation Orders and other environmental factors which will influence surface water drainage. This information is used to establish how surface water currently drains from a site and determine how future surface water runoff from a development could be sustainably managed. 

 

As part of the study the existing surface water runoff rates are determined for several return period events and potential surface water discharge options investigated, in the following order of preference (referred to as the Drainage Hierarchy):

  1. Store rainwater for later use 

  2. Infiltration to ground (whether the ground conditions and underlying geology is suitable to allow water to soak into the ground) 

  3. Discharge to a watercourse

  4. Discharge to a surface water sewer/drain

  5. Discharge to a combined sewer

 

The general aim of a Surface Water Drainage Strategy is to demonstrate to the Local Authority that surface water runoff from a proposed development can be managed as close to its source as possible through the use of SuDS, follows the discharge hierarchy (above), and will not cause an increased flood risk to future site users or third party land. 

 

Whilst the specific requirements of a Surface Water Drainage Strategy vary between Local Planning Authorities, and are dependent on localised conditions, it is becoming increasingly common for Local Planning Authorities and Lead Local Flood Authorities to ask developers to confirm how post development surface water runoff will be managed from their development site at the early stages of the planning process.

What is a Surface Water Drainage Strategy

What are SuDS?

SuDS or Sustainable Drainage Systems are a natural approach to managing drainage around a development and offer an alternative to channelling surface water through a network of pipes and sewers. 

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Sustainable Drainage Systems mimic natural processes and typically manage precipitation close to where it falls. SuDS can be used within a development scheme to slow down, store and convey surface water runoff before it soaks into the ground (via infiltration) or is discharged at a controlled rate to a waterbody or sewer. 

When used effectively SuDS can provide not only attenuation storage for a development but also offer wider environmental benefits including improvements to water quality, biodiversity enhancement and amenity space for future site users. Referred to as the four pillars of SuDS Design (see right).

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It is likely that a proposed drainage scheme will incorporate more than one SuDS feature to achieve, where possible, the four pillars of SuDS design. When two or more features are connected a SuDS management train is created, sometimes referred to as a treatment train.

Four Pillars of SuDS design.jpg
What are SuDS

Types of SuDS

Below is a list of some SuDS features which may be suitable for managing surface water runoff within your development, dependent on site-specific constraints and characteristics: 

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  • Rainwater Harvesting 

  • Green Roofs 

  • Rain Gardens

  • Swales 

  • Filter Strips 

  • Ponds 

  • Soakaways

  • Infiltration basins

  • Pervious Pavements 

  • Attenuation Storage Tanks 

 

Different types of SuDS are suitable for different developments, talk to one of our team to find out more. 

IMG_5050.HEIC
Types of SuDS

What can GeoSon provide?

  • Friendly, professional advice at the other end of the phone. If you are unsure of whether you need a Surface Water Drainage Strategy or would like to discuss comments you have received from the Local Authority, Lead Local Flood Authority or Environment Agency please get in touch with one of our team. 

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  • A cost effective Surface Water Drainage Strategy written in accordance with Local and National Planning Policy.

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  • An initial review of the site characteristics (using available information) to identify any drainage constraints and potential SuDS opportunities assoicated with your development. These will typically be discussed within a Design Team Meeting with the architect, client and any key consultants prior to commencement of the Drainage Strategy. 

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  • A collaborative approach with you and other key consultants working on the project to reduce duplication of work and produce the best scheme for your site.

 

  • Calculations for initial sizing of SuDS features using industry best software and a plan view of the SuDS layout superimposed onto your proposed site layout to give you the best chance of planning success.

Contact Us

Get in touch with one of our consultants for a free,

no-obligation quotation today

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E: info@geoson.co.uk

T: 0117 441 4993

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