15.1 A good supply of water resources is essential to health, quality of life and many business processes. However, water-related issues are particularly important to Salford as a result of significant parts of its urban area being at risk of river and/or surface water flooding, and the relatively poor quality of some of its watercourses.
15.2 Minimising the risk and potential impacts of flooding, taking into account the likely impacts of climate change, will be essential to ensuring that Salford continues to be an attractive location for investment and provides a good quality of life for its residents. Many prosperous cities across the world, such as London, successfully manage the risk of flooding with the need to accommodate large levels of development. The economic and social benefits of continuing to secure investment within areas of Salford that could be subject to flooding are considered to significantly outweigh the potential risks and costs. Some of these areas are fundamental to the prosperity of Greater Manchester, whilst others need investment to support their regeneration and to ensure that they can more actively contribute to and share in the city’s economic growth. They are also central to the overall development strategy and helping to reduce the need to travel.
15.3 The emphasis is therefore on ensuring that the scale of flood risk is minimised as far as possible, for example by seeking additional flood control measures and reducing the surface water runoff from new developments, and ensuring that buildings are appropriately sited and designed so as to minimise the potential impacts in the event of a flood. When combined with the relocation of vulnerable uses, and the replacement of some existing buildings with more flood resilient designs, this should ensure that the Local Plan helps to support continued economic growth whilst reducing the overall economic and social impacts in the event of a flood.
15.4 Some of the measures aimed at reducing flood risk, such as minimising surface water runoff and increasing the use of sustainable drainage systems, should also help to address problems of water quality in the city’s watercourses. However, specific investment in improving the oxygen levels within the Manchester Ship Canal will also be required. This will help to ensure that European targets for water quality are met by the end of the plan period.
A comprehensive and integrated approach to the management of water resources will be taken, enabling significant levels of development to be delivered in accessible locations in an environmentally sensitive way. This will include:
Reasoned justification
15.5 Water-related issues often have a major impact on the scale and form of development that is appropriate. Unlike some other parts of the country, water supply and wastewater treatment are not a significant constraint on the total amount of development that can be accommodated within Salford during the Local Plan period, although some further investment will be required to improve functionality and to facilitate individual new developments.
15.6 Flood risk is a much more important influence within Salford, with some of the most accessible, economically important and socially deprived areas being at a significant risk of flooding. It is unrealistic to adopt a development strategy based on significantly restricting additional investment within these areas, as this would effectively involve abandoning existing communities, and could constrain the future success of key economic areas. The emphasis is therefore instead on ensuring that flood risk is appropriately managed through a combination of measures. This will mean that some new developments will be at risk of flooding, but provided that such development is appropriately designed and adequate flood response plans are in place then it is considered that the benefits of securing major investment in these parts of the city significantly outweigh the likely impacts of any flood events. This investment will also enable some existing buildings that would be badly affected by a flood to be replaced by new buildings that are designed to be much more flood resilient. Overall, the number of people who live or work in a flood risk area will see an increase, but the number who would be significantly affected by a flood event should decrease, providing a more sustainable position than at present.
The Thirlmere Aqueduct and the West East Link Main will be protected from development that could compromise their physical integrity or effective maintenance.
Development should minimise water use as far as practicable by incorporating appropriate water efficiency and water recycling measures.
Reasoned justification
15.7 Salford falls within United Utilities’ Integrated Resource Zone which covers much of the North West region. Latest forecasts suggest that there ”we have more water than we need in the Integrated Resource Zone and lots of potential to make more water available”(22). Consequently, the total available water supply should not act as a constraint on the scale of development within Salford during the Local Plan period, but it is still more sustainable for new developments to be designed to use water efficiently,for example in terms of reducing greenhouse gas emissions associated with water treatment, and take pressure off wastewater treatment works.
15.8 The Thirlmere Aqueduct is the most important piece of water supply infrastructure in the city, and forms part of the Greater Manchester ring main which serves the majority of the conurbation. The new West East Link Main connects the water supply systems that serve the Manchester and Liverpool City Regions, enabling water to be moved around more easily to respond to the challenges of climate change, statutory compliance and maintenance. It is therefore essential that these major pieces of infrastructure are protected from any inappropriate development that could adversely impact on them.
Reference:
(22) “Final Water Resources Management Plan” – United Utilities (March 2015), p10
The water quality of Salford’s water bodies will be protected and enhanced, including through the following measures:
Reasoned justification
15.9 The EU Water Framework Directive sets challenging targets for the ecological and chemical status of surface waters. Working towards them will take a combination of measures, including minimising pollution from developments, investing in wastewater treatment, and delivering individual water quality improvement projects.
15.10 Significant investment in wastewater treatment works serving Salford has been made in recent years. United Utilities is monitoring the need for further investment in its wastewater treatment works so that this can be submitted as part of future 5 year investment submissions to be considered by its regulator. New sewerage infrastructure may be required to serve some of the larger development proposals included in the Local Plan, and this will be investigated with United Utilities.
15.11 Even with improvements to the wastewater treatment works in Salford and adjoining areas, controls over polluting activities, and restrictions on surface water discharge to the sewerage network, other measures will be required to ensure that the water quality within the Manchester Ship Canal is improved. This will be particularly important at Salford Quays given the prominence of the area and the proposed scale of investment. A former scheme to pump liquid oxygen into Salford Quays turning basin was successful at improving the dissolved oxygen levels in this location but was not a sustainable long-term solution. A new system of compressors and underwater helixors within the canal commenced in 2012. This process of aeration raises the oxygen content of the water, improving the water quality and the environment for aquatic life. The city council will work with key partners including Trafford Metropolitan Borough Council, United Utilities, the Environment Agency and the Manchester Ship Canal Company to identify a funding mechanism for this more cost-effective long-term solution that could be extended further down the Manchester Ship Canal.
15.12 The Environment Agency has identified around 2,000 Groundwater Source Protection Zones across the country which are intended to ensure that groundwater sources used for public drinking water are not adversely affected by contamination. The inner protection zone represents the area within which water takes 50 days or less to reach the groundwater source from any point below the water table, the outer protection zone takes less than 400 days, and the source catchment protection zone relates to the entire area from which there is discharge to the groundwater source. The presence of these zones may lead to restriction on the activities that can take place within them.
Structures and other features that help to reduce the risk of flooding or mitigate its impacts will be protected, including the flood basins at Littleton Road and Castle Irwell. Their loss, alteration or replacement will only be permitted where there would be no increase in flood risk.
Opportunities for further improvements in flood mitigation in Salford will be sought, potentially including through the provision of new open space in the Cambridge area.
The city council will work with other local authorities and the Environment Agency to identify the potential for additional flood water storage upstream of Salford.
Reasoned justification
15.13 The city council will use its powers under the Flood and Water Management Act 2010 to identify, protect and ensure the maintenance of structures and features that affect flooding. Planning controls will be coordinated with this regime, and developments will not be permitted where they would adversely affect infrastructure that helps to reduce the risk and impacts of flooding.
15.14 The River Irwell Flood Control Scheme currently protects Lower Kersal, Charlestown and Lower Broughton from river flooding to a 1 in 75 year standard, making some allowance for climate change. The completion of the second flood basin at Castle Irwell will increase the level of protection to 1 in 100 years. However, further measures for reducing flood risk will be sought, in order to better protect the residents and business of Salford. The coordinated improvement of Cambridge would offer the potential to deliver a major new open space that could provide additional flood water storage, similar to Green Grosvenor Park in Lower Broughton.
15.15 If flood risk is to be minimised within Salford then it will be essential that an integrated approach is taken across the whole of the River Irwell’s catchment, and the Catchment Flood Risk Management Plan will be a key vehicle for this. It would seem likely that significant interventions will be necessary upstream of Salford, both in terms of additional flood storage and the reduction of surface water runoff. This is highlighted as a priority in the Greater Manchester Spatial Framework.
Development will not be permitted where it would:
1A) Be subject to an unacceptable risk of flooding, with the acceptability of any risk being determined having regard to:
a) The likely frequency of a flood event;
b) The likely depth and velocity of any flood waters;
c) The vulnerability of the use;
d) The potential impacts on any users of the development; and
e) The potential impacts on any buildings and other structures;
1B) Materially increase the risk of flooding elsewhere;
1C) Result in an unacceptable maintenance liability in terms of dealing with flood-related issues; or
1D) Require unduly complicated or burdensome emergency planning procedures.
Within areas that would be subject to a 1 in 100 year risk of flooding or more (not taking into account flood defences), the following uses will not be permitted:
2A) Police stations, ambulance stations, fire stations, command centres and telecommunications required to be operational during flooding;
2B) Basement dwellings;
2C) Caravans, mobile homes and park homes intended for permanent use, including sites for gypsies, travellers and travelling showpeople; and
2D) Installations requiring hazardous substances consent, except where there is an essential need.
Development that would be subject to a 1 in 1,000 year risk of flooding or more should:
3A) Be designed to minimise the impact of any flooding, in a way that is proportionate to the level of flood risk;
3B) Broadly maintain, and wherever possible increase, the flood water storage capacity of the flood cell within which it is located;
3C) Enable the appropriate flow of flood waters;
3D) Have safe and clearly identified access and egress routes, or a safe refuge, to be used in the event of a flood; and
3E) Have clear evacuation procedures in the event of a flood, and be fully integrated into the city’s emergency planning systems.
Flood risk assessments
A site-specific flood risk assessment should be submitted with any planning application for development that would:
4A) Potentially increase the risk or impacts of flooding; and
4B) Be located on:
a) Any site within Flood Zones 2 or 3;
b) Any site elsewhere that is known to be at significant risk from surface water, sewer or groundwater flooding;
c) Any site within a critical drainage area measuring 0.5 hectares or more; or
d) Any other site in the city measuring 1 hectare or more.
The flood risk assessment should consider all types of flooding and the relationship between them, including that associated with rivers, canals, reservoirs, surface water, sewers and groundwater.
The level of detail in the flood risk assessment should be proportionate to the potential risk and impact of flooding that the development would result in or to which it would be subject.
Definitions
For the purposes of this policy, all assessments of flood risk should take full account of the likely implications of climate change.
Reasoned justification
15.16 Based on the 2011 Strategic Flood Risk Assessment, approximately 3.6% of Salford’s land area and around 1,664 homes would be adversely affected by a 1 in 100 year flood event(23), with significant additional areas being at risk in a 1 in 1,000 year event(24). The main source of this flood risk is the River Irwell, although there is some limited flood risk associated with several of the city’s other watercourses, surface water, groundwater and sewers.
15.17 National planning policy sets some requirements for managing flood risk, based largely around a ‘Sequential Test’ and an ‘Exception Test’. The Sequential Test seeks to steer development to areas with the lowest probability of flooding, with this being particularly important for the uses that are most vulnerable in the event of a flood. Some uses are considered so vulnerable that it would be inappropriate for them to be located in the highest risk areas. Where such uses already exist in those locations, the city council will work with occupants to find alternative sites wherever possible. If development proposed for a site at risk of flooding can meet the Sequential Test then, for more vulnerable uses, it also needs to pass the Exception Test, which essentially requires it to be demonstrated that the sustainability benefits for the community outweigh the flood risk, the development will be safe, and that it will not increase the risk of flooding elsewhere.
15.18 Given the scale and extent of flood risk in Salford, it is essential that a rigorous approach to assessing the flood-related implications of developments is taken. Site-specific flood risk assessments are an important part of this, and these should have regard to the strategic flood risk assessment for Salford and any other relevant information on flood risk. Critical drainage areas were initially defined within the strategic flood risk assessment and may be refined by subsequent information. It will only be appropriate to permit development where it can be clearly demonstrated that there would be no unacceptable risk or impact of flooding, either on the development itself or elsewhere. This will require developers to give very careful consideration to the type of uses proposed, their location and the detailed design of their developments, and to consider the implications not just for their own site but for the wider area and locations downstream. This may require innovative design solutions to reduce the risk and impacts of flooding to an acceptable level. It will also be important to ensure that the implications of any flood event can be successfully managed in practice, and detailed consideration of emergency planning and evacuation requirements will be vital in this regard.
References:
(23) A 1 in 100 year flood event is an event that has a 1% chance of occurring in any one year.
(24) A 1 in 1,000 year flood event is an event that has a 0.1% chance of occurring in any one year.
Surface water should be managed in a way that helps to minimise the risk of flooding.
Developments should use all practicable measures to:
In terms of point 1 above, as a minimum there should be where practicable:
A) For greenfield sites, no net increase in the rate of surface water discharge
B) For previously developed sites, a reduction of at least 50% in the rate of surface water discharge, or a reduction to equivalent greenfield rates, whichever allows the greater discharge
Exceptions may be made where it is necessary to move surface water away from a site more quickly in order to help mitigate serious flood risk problems in the local area.
On-site measures to deal with surface water should be designed as multi-functional pieces of green infrastructure wherever possible.
Reasoned justification
15.19 The Flood and Water Management Act 2010 introduced new responsibilities for the city council relating to the approval of proposed drainage systems in new developments and redevelopments, subject to certain thresholds and exemptions, having regard to minimum national standards. This policy should be read in conjunction with these statutory requirements.
15.20 Given the significant risk of surface water and river flooding affecting many parts of Salford, it will be important to minimise the amount of surface water runoff and discharge from development sites across the city. This could be done for example through the use of porous materials to allow surface water to infiltrate the ground, trenches and soakaways, rainwater harvesting and green roofs. Such features should be also designed to minimise surface water pollution, aiding compliance with the EU Water Framework Directive, for example through the use of filters, membranes and reed beds. It should be noted that some drainage solutions may not be appropriate within the Groundwater Source Protection Zones identified under Policy WA3.
15.21 The range of different drainage solutions available means that it should be possible to comply with this policy on the vast majority of sites. However, it is recognised that it may not be practicable to significantly reduce surface water runoff on some small sites. The identification of measures should have regard to best practice as well as site constraints.
15.22 The wider benefits of investment in drainage systems should be maximised as far as possible, especially by designing them to form part of the city’s green infrastructure network. There are particular opportunities to provide wildlife habitats, supporting the objective of significantly increasing Salford’s overall biodiversity value. Such benefits will be most effectively achieved by designing sustainable drainage systems into the site layout at an early stage.
15.23 There may be limited circumstances where there would be clear benefits from moving surface water away from a site quickly, because dealing with it all on site would exacerbate the risk of flooding in the surrounding area. This is only likely to be the case where water can be discharged quickly into large watercourses such as the River Irwell before their flows peak. This exception will not apply where it is only the development site that would suffer from an increased flood risk.
15.24 The discharge of surface water to the combined sewerage network can lead to the hydraulic capacity of that network and some of Salford’s wastewater treatment works and assets being exceeded. This results in intermittent discharges of storm sewage from those assets into the city’s watercourses, which have an adverse impact on water quality. Surface water discharge to the sewerage network can also result in local sewer flooding, due to the limited network capacity in some areas. It is therefore necessary to ensure that new developments across the whole city, including those on previously developed land, do not discharge any surface water to the combined sewerage network (either directly or indirectly).
Monitoring
15.25 The main indicators that will be used to monitor this chapter are:
| Indicator | Target |
| Percentage of surface water bodies of at least good ecological status or potential | 100% by 2035 |
| Planning applications approved contrary to Environment Agency advice on flood risk | Zero (2015-2035) |