Water Environment and Flood Risk - Planning Guidance

Responsible management of the water environment is an important part of responding to the ongoing climate emergency. At a regional level, the Glasgow City Region Adaptation Strategy and Action Plan (Climate Ready Clyde, 2021) aims to ensure Glasgow City Region’s economy, society and environment is not only prepared for, but continues to flourish in the face of, the impacts arising from the climate crisis. A number of key risks to the water environment are identified, including:

• Risk to soil stock from changes in temperature and water regime.
• Risk to crops and livestock from changes to water regime.
• Risk to freshwater biodiversity from pests, invasive species and disease.
• Risks to new and existing business sites from river, surface water and coastal flooding.

In response to these risks, the Council has a responsibility to deliver nature-based solutions for resilient, blue-green ecosystems, landscapes and neighbourhoods.

The Council is also in process of preparing a local Climate Action Plan, which will commit the Council to placing climate change mitigation and adaptation, the green economy and biodiversity at the heart of its decision-making. This will include objectives relating to water management and the likely impacts of climate change on flooding and drainage.

The aim of a Surface Water Management Plan (SWMP) is to reduce the risk of surface water flooding in the most sustainable way, as required under the Flood Risk Management (Scotland) Act 2009 (the ‘Flood Act’).

SWMPs set out the long-term vision for sustainably managing surface water flooding in an area and the actions needed to achieve that vision, and will take an iterative approach. Any proposed study area will be monitored, reviewed and updated within the timescales in relation to Flood Risk Management Planning cycles and new flood risk information.

To meet the Council’s responsibilities under the Flood Act and the vision of the Metropolitan Glasgow Strategic Drainage Partnership (MGSDP), the Council is undertaking studies to promote a number of SWMP measures across the Council area. Partnerships set up under the Flood Act allow the Council to work closely with Scottish Water to minimise flood risk from surface water sewers, which are the responsibility of Scottish Water.

SWMPs will include a range of measures to manage, attenuate and route surface water to less vulnerable areas, thus minimising the risk of flooding. In addition to water management, the use of SWMPs will aid the Council in meeting a number of other objectives with regards to climate change adaptation, green networks and place making.

Any development that will have a significant impact on local surface water systems or the water environment will be expected to support the objectives of the SWMP. The planning authority may request further information depending on the scale and nature of any proposal.

Where a development proposal represents an opportunity to deliver improvements or minimise surface water flood risk, developer contributions proportionate to the cost of the development itself may be secured to ensure these improvements are realised. Further information can be found in the Council’s Developer Contributions guidance note.

The Metropolitan Glasgow Strategic Drainage Partnership (MGSDP) is a collaborative partnership formed by organisations involved with the operation of the sewerage and drainage network within the metropolitan Glasgow area. It is identified as a 'National Development' within National Planning Framework 3 (NPF3) - a nationally-significant exemplar of catchment-scale water and drainage infrastructure planning.

Graphic illustrating various components of the vision to 2060The MGSDP 2060 Vision is to transform how the city region manages rainfall to end uncontrolled flooding and improve water quality. The vision will be realised through partnership working and will be shaped by eight Guiding Principles:

• Enhancement of our urban biodiversity and landscape
• Reconnection of our waterways
• Design for the severity of the rain
• Presumption that surface water will be kept on the surface
• Creation of an integrated system of blue- green networks
• Integrated urban master planning and design
• Sustainable and affordable drainage solutions
• Climate-change ready.

Delivery of the MGSDP Vision and Objectives, in line with the Guiding Principles, will help to sustainably drain the Glasgow City Region, better service existing communities, unlock potential development sites and build greater resilience to long-term climate change, ensuring that aspirations for regeneration and growth are supported by improved infrastructure capacity.

Policy 18 of LDP2 aligns with these principles and applicants must ensure that the MGSDP Objectives and Vision are supported as part of the design process for all new developments. Further information can be viewed via the MGSDP website.

The European Community Water Framework Directive (WFD) required the creation of River Basin Management Plans (RBMPs). Statutory objectives are set for Scottish waters through River Basin Management Planning. These objectives are based on ecological assessments and economic judgments. The plans cover all types of water body, e.g. rivers, lochs, lakes, estuaries, coastal waters and groundwater.

Each RBMP describes:

• The current condition of the water bodies in the relevant river basin
• Where ongoing or historic activities are reducing the quality of the water bodies
• The actions required to ensure that ‘Protected Areas’ are up to required standards
• The actions needed to deliver environmental improvements to water bodies over the following six years and in the longer term (up until 2027).

'Protected Areas' include drinking waters, shellfish waters, bathing waters, and waters designated for plants and animals (Special Areas for Conservation and Special Protection Areas).

The Scottish Environment Protection Agency (SEPA) is the lead authority to ensure compliance with WFD requirements. The overall aim is for 98% of Scotland’s waters to be in a good condition by 2027, progressively implemented through three RBMP cycles (2009-2015, 2015-2021 and 2021-2027).

The RBMP has identified the following key pressures on the water environment in Scotland:

• Morphological alterations (e.g. modifications to beds, banks and shores as the result of historical engineering and urban development)
• Diffuse source pollution (e.g. agriculture, urban development)
• Point source pollution (e.g. the discharge of sewage, manufacturing and quarrying)
• Abstraction and flow regulation (e.g. alterations to water flows and levels as the result of electricity generation and public water supplies)
• Invasive non-native species.

East Dunbartonshire Council is designated as a ‘responsible authority’ and is required to:

1. Exercise its designated functions to secure compliance with the water framework directive.
2. In doing so, have regard to social and economic impacts, promote sustainable flood risk management and contribute to the achievement of sustainable development.
3. As far as practical, adopt an integrated approach by co-operating with other responsible authorities to co-ordinate respective functions.

The Town and Country Planning (Development Planning) (Scotland) Regulations 2008 require the development plan to have regard to the RBMP. In turn, decisions on planning applications are required to take account of the provisions of the development plan and any other material consideration. SEPA, in partnership with other public bodies, industry and land managers, has a key role to play in protecting and improving the water environment. This includes the regulation of activities that may affect it. SEPA also supports planning authorities to align and integrate RBMP objectives into land use planning and flood risk management. The main ways in which this can be achieved via the planning system include:

• Improving physical condition: Working with the Scottish Government and other public bodies and responsible authorities, SEPA oversees the improvement and physical condition of 309 water bodies throughout Scotland.
• Preventing the spread of invasive non-native species: SEPA will continue to support the approach set out in the supplementary plan Managing invasive non-native species in Scotland's water environment: a supplementary plan to the river basin management plan.

Please note, East Dunbartonshire Council’s Natural Environment Planning Guidance (2018) also provides further information on the regulation of invasive species on proposed development sites (annex C).

Any development that will have a significant impact on the water environment will be expected to support the objectives of the RBMP. The planning authority may request further data via the SEPA hub, depending on the scale and nature of the proposal.

Where a development proposal represents an opportunity to deliver improvements to water body status/potential, developer contributions proportionate to the cost of the development itself may be secured to ensure these improvements are realised.

Improvements put in place to protect and enhance the water environment can also deliver multiple benefits in terms of other key local authority objectives, e.g. extending and enhancing green networks, enhancing biodiversity, climate change and open space targets, reducing flood risk and making provision for recreation.

The planning authority will work with SEPA to ensure the achievement of these objectives through the development management process. More information about the actions or measures underway, or planned, in different areas is available on SEPA’s RBMP information sources(link is external) page. This includes links to an interactive ‘Water Environment Hub’, which provides data on different aspects of the water environment at a local authority level. This includes data on the following:

• Overall condition
• Water quality
• Physical condition
• Access for fish migration
• Water flows and levels
• Freedom from invasive species

At a national level, the flood risk framework sets out three categories of coastal and watercourse flood risk. These are as follows:

• Little or No Risk – annual probability of coastal or watercourse flooding is less than 0.1% (1:1000 years)
  
  • No constraints due to coastal or watercourse flooding.
    
    
• Low to Medium Risk – annual probability of coastal or watercourse flooding is between 0.1% and 0.5% (1:1000 to 1:200 years)
  • Suitable for most development. A flood risk assessment may be required at the upper end of the probability range (i.e. close to 0.5%), and for essential infrastructure and the most vulnerable uses. Water resistant materials and construction may be required.
  • Generally not suitable for civil infrastructure. Where civil infrastructure must be located in these areas or is being substantially extended, it should be designed to be capable of remaining operational and accessible during extreme flood events.
    
    
• Medium to High Risk – annual probability of coastal or watercourse flooding is greater than 0.5% (1:200 years) may be suitable for:
  
  
• residential, institutional, commercial and industrial development within built-up areas provided flood protection measures to the appropriate standard already exist and are maintained, are under construction, or are a planned measure in a current flood risk management plan;
• essential infrastructure within built-up areas, designed and constructed to remain operational during floods and not impede water flow;
• some recreational, sport, amenity and nature conservation uses, provided appropriate evacuation procedures are in place; and
• job-related accommodation, e.g. for caretakers or operational staff.

Generally not suitable for:

• civil infrastructure and the most vulnerable uses
• additional development in undeveloped and sparsely developed areas, unless a location is essential for operational reasons, e.g. for navigation and water-based recreation, agriculture, transport or utilities infrastructure (which should be designed and constructed to be operational during floods and not impede water flow), and an alternative, lower risk location is not available; and
• new caravan and camping sites.
• Where built development is permitted, measures to protect against or manage flood risk will be required and any loss of flood storage capacity mitigated to achieve a neutral or better outcome.
• Water-resistant materials and construction should be used where appropriate. Elevated buildings on structures such as stilts are unlikely to be acceptable.

Further detail on what types of development may be permissible in flood risk areas can be found in SEPAs ‘Flood Risk and Land Use Vulnerability Guidance’.

Flood protection schemes can reduce flood risk, but cannot eliminate it entirely. Their primary purpose is to protect existing development from flood risk rather than to facilitate new development. For this reason the principle of avoidance should be adhered to for any proposed development in areas protected by such schemes.

Certain developments may be acceptable behind an existing or planned scheme in a built-up area. These fall into four main categories:

1. Water-compatible developments and essential infrastructure that is designed to remain operational during flood events
2. Development that does not increase overall flood risk
3. The principle of the development has been established in an up-to-date, adopted development plan (including the National Planning Framework) with due consideration of flood risk
4. The scheme is built to the minimum appropriate standard for the land use vulnerability category of the proposed development as defined below:

• Water compatible uses
  No minimum standard
  
  
• Essential infrastructure (designed and constructed to remain operational during a flood)
  No minimum standard
  
  
• Least vulnerable uses
  0.5% AEP (200 year) standard of protection
  
  
• Highly vulnerable uses
  0.5% (200 year) plus climate change standard of protection
  
  

Formal flood protection schemes are those which have been/are being promoted through relevant legislation (i.e. Flood Prevention (Scotland) Act 1961 (as amended in 1997), the Flood Risk Management (Scotland) Act 2009 or Coast Protection Act 1949). Informal flood defences are proposals that have been/are being brought forward outwith this legislation. Any protection offered by informal flood defences would not be taken into account when considering development behind or benefitting from them. Such proposals would be considered within the context of the flood risk framework as if the scheme did not exist. This is because the structural condition and design standard of such schemes may be uncertain and they therefore pose a level of risk to any proposed development behind or benefitting from them.

Developments that introduce vulnerable uses will not be considered acceptable behind a flood protection scheme. These includes uses such as civil infrastructure, basement dwellings, nurseries and hazardous substance installations. The full classification of most vulnerable uses is detailed within SEPA's Flood Risk and Land Use Vulnerability Guidance. The consequences of any residual flood risk would be too significant for developments within this land use category.

Applicants must ensure that the following principles have been met, for proposals within areas that are subject to existing flood risk:

• Infrastructure and buildings should be designed to be free from surface water flooding in rainfall events where the annual probability of occurrence is greater than 0.5% (1:200 year) – see SEPA flood map.
• Proposed developments with complex surface water hazards should ensure that the surface water flood risk is adequately assessed and managed within the site boundary (more strategic solutions are also acceptable, provided they are able to be secured via the land-use planning process).
• Development must be located outwith the functional floodplain of nearby watercourses.
• Development should not take place within a flow path (i.e. natural, modified or SuDS exceedance flow path), as this could increase flood risk to existing as well as any new development. Note also that any land raising in areas where surface water flows and ponds may only serve to increase flood risk to existing receptors by deflecting water towards them.
• Land raising will not be permitted within the functional floodplain
• Residential development in lower ground/basement floors should be avoided where surface water flood risk is significant and cannot be mitigated, as it can pose a risk to life. This is due to potential rapid inundation where water could pour in from above head height.
• A Flood Risk Assessment should be used to inform the siting, layout, design and capacity of development on the site in a way that avoids an increase in flood risk on and off site and ensures that there is safe dry pedestrian access and egress at times of flood. This means the provision of a safe and flood-free route during the relevant flood probability event that enables the free movement of people of all abilities (on foot or with assistance) both to and from a secure place that is connected to ground above the design flood level and/or wider area.
• Finished floor levels must be set 600mm above the design flood level where appropriate and practicable in order to provide an allowance for freeboard.
• Buildings and other structures should be designed to be flood resistant and resilient. Flood- resilient buildings are designed to reduce the impact of flood water entering the building so that damage is minimised. In comparison, flood-resistant buildings are designed to prevent or minimise the entry of water into the building in the first place. The appropriate resilience and resistance measures will depend on the characteristics of the design flood; this includes the estimated flow velocity, inundation rate, depth that flood water will reach in the building and the duration of the flood event. Specific guidance on flood resilient and resistant construction techniques can be found in the CIRIA 2019 code of practice and guidance for property flood resilience.
• Where development is a replacement for existing development of the same type, opportunities for flood risk betterment should be explored.

Further information on the above can be viewed in SEPA's ‘Flood Risk Standing Advice for Planning Authorities and Developers’ document.

Subject to agreement with the Council’s Flood Risk team, and in compliance with the relevant legislation, a culverted watercourse may be diverted. However, the final form and alignment of any diversion will be required to maintain existing pass-forward flows or flows specified by the Council and have a self-cleansing velocity. In addition, consideration should be given to the following design elements:

1. Opportunities for day-lighting
2. Removal of site-specific flow restrictions
3. Improving access to the culvert for maintenance
4. Opportunity to create multi-functional green infrastructure, including enhancements to landscape, habitats and access/recreation
5. Removal of barriers to fish movement.

Domestic extensions and alterations have the potential to impact on local flood risk, particularly in a cumulative sense. Similarly, small structures and outbuildings have the potential to impact upon flood risk elsewhere. This includes garages, sheds, conservatories, greenhouses and other buildings that are incidental to the enjoyment of a main residential dwelling houses. The Council will therefore expect the following flood design matters to be demonstrated. This applies to any residential extension or outbuilding, including the provision of new overnight accommodation/bedrooms, but excluding the formation of an entirely new dwelling:

• The incorporation of flood resistant and resilient materials and design, and the raising of finished floor levels where practicable. The CIRIA 2019 code of practice and guidance for property flood resilience is a useful source of information and you may wish to consult with the local authority Building Standards team.
• Safe and flood-free access and egress should be provided where possible. This means the provision of a safe and flood-free route during the relevant flood probability event that enables the free movement of people of all abilities (on foot or with assistance) both to and from a secure place that is connected to ground above the design flood level and/or wider area.
• Finished floor levels should be set 600mm above the design flood level where appropriate and practicable in order to provide an allowance for freeboard. An allowance for climate change should be included when calculating the design flood level, independently of an allowance for freeboard, as per SEPA's Guidance on Climate Change Allowances for Flood Risk Assessment in Land Use Planning.
• A 6m minimum (for channels less than 1m in width and increasing proportionally to channel width) undeveloped buffer strip should be provided in perpetuity between all development types and watercourses, allowing space for natural fluvial processes to occur (as well as other attendant environmental benefits, not limited to but including biodiversity, open space, channel maintenance, pollution reduction and river restoration). It is important to highlight that buffer strips do not mitigate any identified flood risk that may exist at a site.

Full advice relating to a range of other development types can be found in SEPA's ‘Flood Risk Standing Advice for Planning Authorities and Developers (2020)'. This includes proposals for essential infrastructure, cemeteries, small-scale street furniture, walls and fences, footpaths and access tracks, car parks, open-sided agricultural buildings and temporary construction accommodation.

A buffer strip is an area between built development and the boundary of a watercourse where no development is permitted. It is maintained in permanent vegetation. Buffer strips can bring multiple benefits, including better soil and water quality. They ensure space for natural fluvial processes to occur and promote biodiversity including the provision of natural habitats. Other key benefits include: contributing to green networks and open space allocations; stabilising banks and reducing soil erosion; reducing pollution from surface water run-off; opportunities to undertake restoration of straightened or realigned watercourses in the future; and the delivery of RBMP and multiple benefits by providing a green-blue network.

The planning authority will seek a buffer strip of a minimum of 6m on either side of the watercourse, however, this should be proportional to the bank width. For example, wider rivers would have a larger buffer strip than a narrow burn. This will be measured from the top of the bank. Please note that 6m is a minimum and developers may be required to allow for a greater width where site-specific issues relating to site conditions, topography, flood risk, pollution-control pressures, physical condition, climate change mitigation, native species habitats, active travel and recreation are known to apply. The following table provides an indication of expected widths, as recommended by SEPA.1

This strip should be kept free from any development in order to allow access to the water body for the purpose of assessment and maintenance, to ensure bank stability, and to aid water and ecological quality. Riparian buffer strips may be secured by a planning condition. Any request to reduce this requirement must be suitably justified to the satisfaction of the Council.

The information below sets out the variety of SuDS techniques and ways they can be implemented. In most cases, above-ground management of surface water will require a combination of these measures, including source control, conveyance and storage in all rainfall events.

Managing water on the surface

Potential Action: Infiltration

For managing ‘every day rain’ – maximise the use of permeable surfaces and vegetation, allowing rain to infiltrate the ground and evaporate into the atmosphere where it falls, creating little or no surface water run-off.

Potential Action: Conveyance

For managing ‘usual rainfall’ - collect, delay and convey rainfall and resultant surface water above ground to watercourses using green infrastructure techniques.

Potential Action: Storage

For managing ‘extreme rainfall’ - delay, store and convey surface water above ground to watercourses using green infrastructure techniques.

Further information on Infiltration, Conveyance, Storage

• Susdrain resource on sustainable drainage: CIRIA publications
• CIRIA C753 (2015) - The SUDS Manual
• CIRIA C728 (2014) Managing urban flooding from heavy rainfall – encouraging the uptake of designing for exceedance
• CIRIA C713 (2012) Retrofitting to manage surface water
• CIRIA C635 (2006) Designing for exceedance in urban drainage: good practice

Potential Action: Restoring urban watercourses

Restore urban watercourses (e.g. restoring floodplains and de-culverting) to reduce flooding from the watercourse itself and provide more opportunities to convey surface water into the natural environment.

Further information on restoring urban watercourses

• SEPA’s Natural Flood Management Handbook

Potential Action: Run-off reduction strategy

Develop what is typically a long-term plan for making whole urban areas more ‘green’ and permeable, whilst reducing impermeable and ‘grey’ engineered surfaces. This allows more rain to infiltrate the ground and encourages evapotranspiration, reducing run-off rates and volumes.

Potential Action: Reducing surface water in the sewer

Identify opportunities to reduce surface water in sewers. Scottish Water is responsible for the sewer network and should therefore be contacted regarding any proposals.

Further information on run-off reduction strategy and reducing surface water in the sewer

• Sheffield City Council Grey to Green Project

Potential Action: Land management

Implement land management actions that reduce the rate and volume of run-off. Run-off from more rural land (‘the urban fringe’) can flood homes, businesses and infrastructure directly and, by significantly increasing flows to the urban area, drainage systems and watercourses can raise flood risk further downstream.

Further information on land management

• SEPA’s Natural Flood Management Handbook

Managing water below the surface

Potential Action: Underground storage

Divert surface water to storage tanks or provide storage in the existing drainage/flood management network.

Potential Action: Underground conveyance

Increase capacity or build new underground pipes for surface water

Potential Action: Modification of culverted watercourses

Increase the capacity of culverted watercourses or divert culverted watercourses.

Source: Surface Water Management Planning Guidance, Scottish Government (2018)

Techniques

Swales - Broad, shallow channels covered by grass or other suitable vegetation. Swales attenuate the surface water flow and allow time for filtration and sedimentation into sub-surface soil in areas where soil porosity is suitable.

Filter Strips - These are wide, gently sloping areas of grass or other dense vegetation that slow and treat run-off from adjacent impermeable areas.

Filter Drains - Filter drains are trenches that are filled with permeable material such as gravel. They work by providing capacity for attenuation. Surface water from paved areas flows into the trenches, is filtered and conveyed to other parts of the site. A perforated pipe may be built into the base of the trench to collect and convey the water.

Permeable Surfaces - Allow rainwater to pass through the surface into an underlying storage layer, where water is stored before infiltration into the ground. They can be designed to fit in with a variety of settings, e.g. permeable paving or gravel surfaces in car parks, garden paths, etc.

Infiltration Basins - Depressions created within the site to store run-off and allow filtration into the ground below.

Infiltration Devices - Dispose of surface water run-off into the ground. Both groundwater and ground conditions must be suitable to receive the volume and quality of water anticipated.

Extended Detention Basins - These are normally dry, though they may have small permanent pools at the inlet and outlet. They are designed to detain larger run-off volumes than infiltration basins as well as providing water quality treatment.

Ponds and Pools - Small but permanent water bodies which provide temporary storage for additional storm run-off above normally-expected water levels. Wet ponds may provide amenity and wildlife benefits, and a sedimentation process to reduce pollution to watercourses. Water may be retained for as long as two or three weeks.

Constructed Wetlands - These are ponds with shallow areas and wetland vegetation to improve pollutant removal and enhance wildlife habitat. They may also be landscaped to provide amenity value. Green Roof Systems - Cover a building’s roof (or walls) with vegetation. They are laid over a drainage layer, with other layers providing protection, waterproofing and insulation. Sedum rather than grass can minimise maintenance.

Below Ground Storage - Enables retention of water for irrigation of green infrastructure.

Please note that no SuDS features should be implemented within a functioning flood plain to avoid the risk of:

• SuDS features becoming redundant during possible inundation from adjacent watercourses
• Risk of contaminants from the development washing to the adjacent watercourses during such events.

Furthermore, any new developments must not impact on the storage capacity or functionality of an existing flood plain.

The level of surface water treatment required depends on the nature of the proposed development (for example, residential or non-residential), the size of development and the environmental risk posed by the development. As a minimum, the Council will expect the following levels of treatment to be provided. For mixed-use developments, the level of treatment required will be determined by the use with the highest sensitivity within the development.

1. Residential developments of fewer than 50 houses and retail/commercial/business parks with car parks of 50 spaces or less require one level of treatment for all hardstanding areas including roads.
2. Residential developments of 50 or more houses and retail/commercial/business parks with car parks of more than 50 spaces require two levels of treatment for all hardstanding areas including roads. An exception is run-off from roofs which requires only one level of treatment. As best practice, the second level of treatment should ideally be a basin or pond.
3. Industrial developments require three levels of treatment for hardstanding areas and two levels of treatment for roads. An exception is run-off from roofs which requires only one level of treatment. As best practice, the second level of treatment should ideally be a basin or pond.
4. All roads schemes require two levels of treatment. For technical guidance on SuDS techniques and treatment for roads please refer to the SuDS for Roads manual.
5. For all developments, run-off from areas subject to particularly high pollution risk (e.g. yard areas, service bays, fuelling areas, pressure washing areas, oil or chemical storage, handling and delivery areas) should be minimised and directed to the foul sewer.

Please note that levels of treatment required may vary depending on other stakeholder and other statutory agency requirements. Further guidance regarding this matter can be found in SEPA’s Regulatory Method (WAT-RM-08) Sustainable Drainage Systems.

Sheffield’s Grey to Green SuDS project has transformed a redundant carriageway in the city centre into a network of sustainable drainage and rain gardens. This not only reduces the area generating surface run-off, but also provides the space to manage the remaining areas more robustly. Newly-created green infrastructure modified as a series of swale cells provides environments to capture, clean, infiltrate, move, and store water. It has improved the city’s resilience to climate change, enhanced the public realm and increased connectivity in the city centre. The project is now attracting investment in new and existing jobs.

Client: Sheffield City Council;

Constructor: North Midland Construction

Before

• Rainfall is drained quickly into pipes, for example via gullies inthe road. This can add to flooding problems and in the case of roads can send pollutants such as oils, heavy metals and microplastics straight to rivers.
• Urban areas disconnected from rivers and streams, where run-off is instead sent to the treatment works in sewers, mixed with foul water. During extreme rainfall events, many of these pipes overflow into rivers, causing pollution.
• Rainwater was always seen as a nuisance to be got rid of. The pipes underground meant 'out of sight and out of mind'. To a large extent this was down to the problems of sanitation of the time – needing to isolate people from water because it may contain disease.

After

• Rain is captured by the existing landscapes or new green infrastructure. Their design holds that water temporarily, even during extreme rainfall events. The everyday rain that washes pollutants from the roads is filtered and broken down by soils and plants.
• Many new large developments now drain to rivers, but care needs to be taken with capturing and treating pollutants. Redirecting water back to the river, but making sure it is done sustainably, mimicking natural process – ‘clean and slow flows’.
• Times have moved on - rainwater and the run- off it creates are seen as important things to manage to prevent flooding and pollution, but also that the landscapes that can do this are places to celebrate the visibility of rainwater. Rainwater is a resource that can irrigate our green networks, keep our urban areas cool and build awareness of natural processes.

Source: Carbon Conscious Places, A&DS

Procedures

Sustainable water management, including potential SuDS measures, must be considered at an early stage in project design in order to determine suitability. Pre-application discussion can be invaluable in developing a common understanding of what is proposed, and to assist the efficient and effective processing of applications. This includes discussions relating to maintenance responsibility. Developers are therefore strongly encouraged to approach the planning authority at the earliest possible stage to explore which combination of SuDS measures, if any, are most appropriate.

If a meeting is thought appropriate, then the developer should submit an outline development concept, in order that all parties to the meeting can come prepared to discuss the criteria for water quantity, quality and amenity issues related to the proposal. This may include related sites upstream and downstream on the relevant watercourses, sewerage systems or groundwater. For any SuDS discharge to the water environment, SEPA should also be consulted in order to provide the appropriate CAR approvals.

Level of information

The level of detail required as part of planning applications will be proportionate to the complexity of the flood risk mechanisms, the site location and the severity of the risk. Applicants must ensure that the information submitted clearly demonstrates that the proposed development is not at risk of flooding and will not increase flood risk elsewhere. The application must also include robust and sustainable drainage proposals. This information should be completed by an appropriate professional, as set out in this document. If the proposed development does not comply with this guidance document, the application may be refused.

Detailed advice and guidance on flood risk is published by SEPA. This includes general guidance on flood risk and advice for an applicant and development management (see Appendix 1). The purpose of a Flood Risk Assessment (FRA) is to investigate the likely probability of flooding at a specific site and to assess the likely risk to the proposed development and to adjacent people and property.

The Council will request a FRA to support a planning application when:

• The proposed development is located close to a watercourse
• The Council has evidence of historical flooding issues relating to the proposed site
• SEPA’s flood map shows the proposed site to be at risk of fluvial or pluvial flood or in close proximity to the inundation of a watercourse in the event of a year flood (plus climate change allowances).

The diagram below may be useful in determining whether a FRA is required. Where there is any doubt concerning the need for a FRA, applicants are strongly advised to consult with the planning authority at the earliest opportunity.

The scope of an FRA will normally depend on the complexity of the flood risk mechanism(s), the site and the severity of the risk. FRAs should identify the source of potential flooding i.e. fluvial, coastal, surface water (pluvial) or combinations of sources of flooding. In some smaller cases, a more basic FRA may be appropriate where the risk is likely to be low. It is therefore advisable to consider the potential outcome of the assessment prior to investing in a detailed FRA. Applicants are strongly advised to use specialist and experienced professional consultants, preferably with experience of the local area.

It is recommended that an appropriate level of FRA be carried out as soon as the site is considered for development. The scope and detail of the FRA required should be discussed with the Council prior to submitting a planning application. The FRA should be completed by a professional with relevant experience in flood risk and drainage design.

Minimum requirements of a Flood Risk Assessment

1. Plans - description of the proposed development including location, size and nature of surrounding area, watercourses and landscape.

2. SEPA flood risk map status.

3. Photos – showing area of proposed development relative to any watercourses or water bodies. Time stamped.

4. Topographic information - existing ground levels, finished floor levels where appropriate, any land raising. Survey data used to assess flood routing/depths.

5. Cross sections - sections should be of an appropriate length to include the application site, the channel bed levels and bank levels of the opposite bank. Additional sections would also be required at keys areas of interest, including structures like bridges and culverts, significant changes in the channel or floodplain width.

6. Structural information – details of any structures – such as culverts, bridges, weirs, and croys – which may influence water levels, should be provided.

7. Other site specific information – overview of existing flood risk, consultation with SEPA and Scottish Water, provision of compensatory storage, results of hydrological modelling, details of proposed flood-resilient materials, existing drainage infrastructure.

Additional technical guidance from SEPA is set out in their Technical Flood Risk Guidance for Stakeholders document.

Applicants should prepare and submit either a drainage statement or Drainage Impact Assessment (DIA), depending on the scale and/or type of proposal. This should be submitted as part of the planning application in principle. The purpose of this requirement is to demonstrate that the development can be effectively drained.

Drainage statement

All developments other than householder or changes of use will need to provide a drainage statement. This should describe the proposed drainage arrangements and connections to a surface water system or Scottish Water drainage network. Plans submitted with the application should include the proposed layout of the drainage proposals, which should include SuDS for attenuation and treatment of surface water.

Drainage statement essential documents checklist

• General description of the development, its size, location and surrounding topography and land uses.

• Description of existing drainage arrangements on-site and any sewers.

• A concept drawing of the development and proposed/likely means of providing foul and surface water drainage.

• Evidence of proposed run-off rates and storage volumes for a variety of return periods.

Drainage Impact Assessments

The need for a Drainage Impact Assessment (DIA) will be determined by the Council on a case-by-case basis, depending on the scale and type of proposal. A DIA is more detailed and should demonstrate the site-specific drainage issues relevant to a proposal and the suitable means of accommodating any identified drainage needs. A checklist setting out specific requirements is set out in Table 4.

In the case of masterplan developments involving more than one developer, the Council will expect all parties to adopt a joint approach to drainage, rather than individual approaches that may result in separate SuDS systems for each aspect of the wider development. The Council will expect this to be considered and agreed as a key part of the masterplan process.

Requirements

• Report including drawings/calculations/figures.
• Description of existing drainage rights/arrangements on site.
• Assessment of pre/post run-off rates, changes in impermeable areas.
• Evidence of proposed run-off rates and storage volumes for a variety of return periods.
• Outline drainage design showing use/application of SuDS, supported by calculations/model results.
• Wastewater drainage proposals, including a letter of agreement from Scottish Water to accept foul flows (if applicable).
• Reporting of on-site infiltration tests (where suitable).
• Proposals relating to discharge rate control methods, receiving water bodies, structures, etc.
• In the case of masterplans, all parties to demonstrate agreement of joint approach to drainage.

The DIA should cover surface water and foul drainage. Early discussions with the Council, SEPA and Scottish Water are encouraged for applications of a significant scale. The drainage strategy should include:

• An indication of the types of measures to be used
• Which measures will be considered in the detailed design
• Evidence of sub-soil porosity and suitability for use of infiltration SuDS
• Pre and post-development run-off calculations to determine the scale of SuDS required
• Assessment of flood risk where this is deemed appropriate
• Proposals for integrating the drainage system into the landscape or required public open space
• Demonstration of good ecological practice including habitat enhancement
• Estimates of land take for different drainage options based on initial calculations carried out to size any significant drainage structures.

By the stage of submitting either a full or reserved matters planning application, a detailed drainage design will be required. Preparing such a design involves five steps:

1. The planning authority will agree with the other regulatory authorities the type of information that needs to be included in the planning application and inform the developer accordingly
2. The developer and drainage designer should liaise as necessary with the regulatory authorities to agree on appropriate criteria
3. The drainage designer should follow the procedures in the SuDS Design Manual for selection of drainage techniques
4. The developer should confirm with the regulatory authorities that the selected techniques are appropriate
5. The drainage designer, in consultation with relevant disciplines as necessary, should follow the guidance in the design manual to produce designs for planning, building warrant, drainage and road construction applications, and to meet the needs of prohibition notices where appropriate.

Prior to the commencement of development works, the applicant will be required to submit to the Council a copy of the appropriate technical approval or consent to discharge to a Scottish Water asset. Technical guidance relating to drainage can be found in the Council’s Flooding and Drainage Guidelines for Developers, 2015.

Urban creep is the conversion of permeable surfaces to impermeable over time. Common examples of this include the resurfacing of front gardens to provide additional parking spaces, extensions to existing buildings and the creation of large patio areas. This can significantly increase surface water run-off and flood risk over time. The consideration of urban creep will be assessed on a site-by-site basis, but is limited to residential development only.

It is important that the appropriate allowance for urban creep is included in the design of the drainage system over the lifetime of the proposed development. The allowances set out below should be applied to the impermeable area within the property curtilage:

Residential development density - dwellings per hectare & Change allowance % of impermeable area

• <25: 10%
• 30: 8%
• 35: 6%
• 45: 4%
• >50: 2%
• Flats and apartments: 0%

Note - where the inclusion of the appropriate allowance would increase the total impermeable area to greater than 100%, 100% should be used as the maximum.

Climate change allowances

Climate change will increase the risk of flooding due to increased rainfall, rising sea levels and population growth. Therefore, a precautionary approach to flood risk that takes account of the predicted effects of climate change will be adopted by the Council. When designing proposals, allowance should be made for climate change as part of a Flood Risk Assessment.

A climate change allowance is a prediction of anticipated change in peak river flow, peak rainfall intensity and sea level rise caused by future climate change. The type of allowance used will depend upon the type of flooding being considered and, for river (fluvial) flooding, the size of catchment.

East Dunbartonshire lies within the Clyde Basin catchment area, which has a projected peak river flow allowance of 49% up to the year 2100 and a peak rainfall intensity allowance of 41% to the year 2100. Further information can be viewed in the SEPA ‘Climate Change Allowances for Flood Risk Assessment in Land Use Planning document (2022).

The role of SEPA

SEPA is responsible for regulating activities that are subject to the Water Environment (Controlled Activities) (Scotland) Regulations 2011 (as amended) (CAR). This includes discharges to the water environment (surface water and foul drainage), and engineering works that impact inland waters. For the most part drainage and other issues that fall within the remit of CAR are now subject to standing advice.

To minimise delay and the risk of complication planning permission and regulatory authorisation should be sought and progressed simultaneously. We recommend that applicants refer to the CAR Practical Guide and the water regulations section of our website in the first instance. Where an activity is subject to a General Binding Rules (GBR) it is incumbent on the applicant to ensure compliance.

The role of Scottish Water

Scottish Water is responsible for providing water and sewerage services across Scotland. It is accountable to the public through the Scottish Government and plays a key role in the land planning and development process in terms of ensuring appropriate connections to water and waste water infrastructure. The following paragraphs outline some key considerations where proposals may require liaison with Scottish Water.

Foul drainage

All developments requiring a foul discharge should be connected to the public sewerage system. The Council recommends that all applicants consult with Scottish Water at the earliest possible stage of the design development to ensure that sufficient capacity is available for connection.

Business and trade effluent

For all business and trade effluent discharges, the Council recommends that the applicant engages with an appointed licensed provider to Scottish Water.

Surface water drainage

If it has been identified that surface water should be discharged to either a combined or a surface water sewer, the Council recommends early engagement with Scottish Water. The applicant will be required to provide evidence of consultation and approval in principle from Scottish Water for the surface water discharge prior to the determination of a planning application.

Public water connection

For any development which will require a new connection to the public water network, the Council recommends that the applicant engages with Scottish Water at the earliest possible opportunity.

A list of Scottish Water’s legal responsibilities in relation to the water environment can be found in Appendix 2.

Applicants will be expected to consider long-term ownership and maintenance responsibilities of the surface water drainage network and associated infrastructure. In particular, all SuDS features which provide a statutory function are adopted or vested by a relevant in-perpetuity body.

Within the curtilage of private properties, responsibility for surface water drainage lies with the owner. Outwith private properties (unless the site is served by a private sewer) statutory responsibility for surface water drainage is split between roads authorities - responsible for the drainage of adopted roads - and water authorities - responsible for drainage of roof run-off and curtilages/other land.

Local authorities (roads authorities) and Scottish Water may enter into agreements for shared drainage. Some agreements provide for a single shared drainage system to drain surface water from properties and from roads. While generally considered to apply to piped sewerage systems, it has been used as the basis for an agreement for maintenance of public above-ground SuDS (including swales or other ground depression features) being the responsibility of the local authority or other, whilst below ground SuDS will be the responsibility of Scottish Water.

The following checklist may be used to ensure that any planning application submitted addresses the key matters covered by this guidance:

• Does the proposal improve the physical environment of a watercourse/water body and therefore improve its water quality?

• Is the development site at risk of flooding from any source?

• Will the development lead to increased flood risk elsewhere?

• Has the need for a Flood Risk Assessment been established?

• Does the proposal include details of how surface and groundwater from the site will be sustainably managed* during construction and post-construction?

• Has a drainage statement or Drainage Impact Assessment been undertaken to the required standard?

• Is it possible to provide safe access and egress during flood events?

• Does the proposal include details of who will be responsible for the ongoing management and maintenance of the SuDS?

• Does the proposal explain how the development proposals will impact on the water environment in relation to any habitats, protected species and/or natural environment designations?

• Are there opportunities to enhance and connect with green or blue infrastructure, providing multiple benefits - including provision of shelter, biodiversity habitats and links, creating attractive public spaces, access and travel, pollution mitigation and food production - while managing surface water?

* in line with the requirements of CIRIA SuDS guidance (currently CIRIA C753 The SuDS Manual) and CIRIA C768 Guidance on the construction of SUDS), the Water Environment (Controlled Activities) (Scotland) Regulations 2011 (CAR) (as amended), (refer to CAR practical guide), and Local Development Plan 2 Policy 18

Catchment

River Kelvin

Length (km)

18.042

Genre

Heavily modified water body

Current Status

Moderate

Target Status 2021

Moderate

Target Status 2027

Good

Comments

Flood risk present

Catchment

River Carron

Length (km)

6.258

Genre

Surface water

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

22.017

Genre

Heavily modified water body

Current Status

Poor

Target Status 2021

Poor

Target Status 2027

Good

Comments

Historic flood issue, but strategic flood defence scheme now in place

Catchment

River Kelvin

Genre

Heavily modified water body

Current Status

Poor

Target Status 2021

Poor

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

8.166

Genre

Heavily modified water body

Current Status

Moderate

Target Status 2021

Moderate

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

4.744

Genre

Heavily modified water body

Current Status

Moderate

Target Status 2021

Moderate

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

7.409

Genre

Surface water

Current Status

Moderate

Target Status 2021

Moderate

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

7.837

Genre

Surface water

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

9.181

Genre

Heavily modified water body

Current Status

Poor

Target Status 2021

Bad

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

15.136

Genre

Surface water

Current Status

Poor

Target Status 2021

Moderate

Target Status 2027

Good

Comments

Flood risk present

Catchment

River Kelvin

Length (km)

5.519

Genre

Surface water

Current Status

Moderate

Target Status 2021

Good

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

8.134

Genre

Heavily modified water body

Current Status

Poor

Target Status 2021

Moderate

Target Status 2027

Good

Catchment

Glasgow Coastal

Length (km)

9.895

Genre

Artificial water body

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Comments

Flood risk at Bishopbriggs

Catchment

River Kelvin

Length (km)

9.811

Genre

Artificial water body

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Catchment

River Kelvin

Length (km)

14.105

Genre

Artificial water body

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Catchment

n/a

Length (km)

n/a

Genre

Bedrock

Current Status

Poor

Target Status 2021

Poor

Target Status 2027

Good

Comments

n/a

Catchment

n/a

Length (km)

n/a

Genre

Bedrock

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Comments

n/a

Catchment

n/a

Length (km)

n/a

Genre

Bedrock

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Comments

n/a

Catchment

n/a

Length (km)

n/a

Genre

Bedrock

Current Status

Good

Target Status 2021

Good

Target Status 2027

Good

Comments

n/a