FAQ’s

The ARC is an exciting initiative seeking to create an innovative commercial structure to enable Leeds businesses to support long-term flood protection for Leeds. The project involves multiple stakeholders from across the public and private sectors to build greater, and greener business resilience. In particular, the project is focussed on addressing the future impact of climate change, to mitigate the predicted increase in frequency and intensity of rainfall that will see a significant increase in the volume of water entering the River Aire and consequently passing down the Aire valley towards Leeds during such an event. ARC is offering the business community in Leeds a proactive opportunity to securing their flood resilience and business continuity whilst contributing to their net-zero and ESG ambitions.

The ARC project will establish a legal entity. This will be a not-for-profit, asset locked Community Interest Company (CIC) with responsibility for ensuring the delivery and maintenance of nature-based, and hydrologically modelled, flood management measures within the Aire Valley to significantly reduce the risk of future flooding in Leeds resulting from the impact of climate change.

This will work in conjunction with the Environment Agency funded, and Leeds City Council operated, Leeds Flood Alleviation Scheme (Leeds FAS). The delivery of ARC will create a highly effective, and proactive ‘first line of defence’; reducing the dependence on the hard engineered flood defences of Leeds FAS.

The headline target for ARC to achieve regarding reducing the flow of water entering Leeds is for a minimum 5% reduction in the peak volume of water flowing into Leeds during a 1 in 200-year storm by 2069. This figure is important as climate modelling tells us that by 2069, a storm equivalent to Storm Desmond, which brought flooding to Leeds in 2015 will see 8% more water flowing into Leeds at its peak.

Underpinning ARC will be a financial model which engages private finance to ensure the maintenance of these measures long into the future, ensuring greater long-term security for both the residents of Leeds, and its business community.

The ARC project is being led by The Rivers Trust and Leeds City Council. Other organisations providing significant input are the Environment Agency (EA), the Aire Rivers Trust (ART) and Nature Finance (NF). In addition, there are several key stakeholders who are supporting and contributing to the project development including, the Yorkshire Wildlife Trust, the White Rose Forest and the Regional Flood and Coastal Committee (RFCC). This project is working in close alignment with the Leeds Flood Alleviation Scheme (Leeds FAS) project team.

ARC will achieve its objectives using Natural Flood Management (NFM). NFM uses natural processes and works with the landscape to slow the flow of water off the land during periods of heavy rainfall. These measures can include planting trees to increase woodland cover, building leaky dams to hold back water; and land management techniques such as soil aeration and grassland conversion. Soil aeration increases the amount of water that can soak into the ground reducing the amount entering becks, streams and ultimately the River Aire. It also means greater amounts of water are ‘held’ in the land for longer, helping to protect against periods of drought. Using extensive and detailed hydrological modelling of the Aire Valley, ARC has identified the priority areas for delivery, and the two most effective NFM measures for use. These are tree planting and soil aeration. This does not mean that we will not implement other NFM measures as ARC will deliver a range of measures to provide a comprehensive and holistic approach.

ARC is not a pilot project, much smaller projects based on a similar model have been successfully delivered elsewhere in the UK (for example in the Wyre catchment). However, ARC is unique in the scale at which it is seeking to deliver NFM and in its engagement with the private sector to develop a consortium of local businesses working together to generate a range of benefits alongside reducing their own flood risk.

‘Peak Flow’ is the maximum flow of a waterbody in response to a storm or period of heavy rainfall. In particular this relates to water ‘running off’ the land immediately after landing as rain. This water quickly finds its way into rivers and streams and when it reaches its highest point is referred to as the ‘Peak Flow’. Factors influencing peak flow include the ability of the landscape to intercept or absorb rainfall as well as the degree to which the ground is saturated. It is important as it represents the highest point at which water levels within the river system will rise during a storm and therefore is the level that flood defences must be able to protect against. ARC’s objective is to reduce the level of the peak flow traveling down the Aire and reaching Leeds by a minimum of 5%.

We recognise that not all companies will contribute to ARC yet will still gain the benefit of a climate resilient catchment. This is unavoidable. However, reduced flood risk is just one of the benefits to be gained by contributing.

ARC represents an opportunity for businesses to demonstrate their commitment to Leeds, the communities of the Aire Valley and to building climate resilience for themselves, their supply chains, and their customers. ARC’s focus on the Aire catchment means that firms can demonstrate their values and corporate social responsibility by acting locally and making a real difference to the environment and to the communities in which they operate. By safeguarding your customers, workforce, and supply chains, together with the infrastructure that allows your businesses to function, you are protecting your future business prosperity.

To recognise where businesses do contribute, ARC will ensure visibility on its website and any publicity materials for those contributing. We will also ensure there is reporting on outputs and outcomes in a format that can be readily used in ESG reporting.

Through the Environment Agency, the government has provided over £200 Million to Leeds to build the Flood Alleviation Scheme (FAS) in and around the city. This has extended to include further funds for tree planting in the Aire Valley. Given the pressures on public finances, there are no additional funds available through this route to cover the cost of the delivery under ARC. The long-term maintenance and monitoring of the ARC delivery requires income from a range of sources including the private sector which may unlock further match funding from the public sector to assist with the cost of delivery. However, the bulk of long-term funding, necessary to ensure maintenance and monitoring of works delivered and to ensure the intervention retains its efficacy and the city continues to enjoy enhanced flood risk reduction, will need to come from the private sector.

The design of Leeds FAS did take into account the predicted impact of climate change. The natural flood management schemes were factored in when deciding the height of the new flood walls. Hard engineered flood management schemes such as Leeds FAS are expensive and intrusive to the city. The greater the level of protection desired, the higher the walls and more prominently the protective measures will need to be built. These are intrusive and Leeds waterfront, a key feature in Leeds’s attractiveness as a place to live and work, would be negatively impacted. Leeds FAS has been built to contain a repeat of the flooding seen on Boxing Day 2015 courtesy of Storm Eva with additional capacity to manage water levels reaching 3% higher. The challenge we face is that scientific modelling shows by 2069, a storm equivalent to 2015’s Storm Eva will see nearly 8% more water surging into Leeds at its peak due to climate change. Forces of nature such as this are incredibly difficult to manage or contain. It is important therefore to add a further ‘ring’ of protection upstream that can provide a proactive defence in addition to the more reactive defences in and around Leeds. By intervening earlier on, before rainfall can reach the river and become a surge, we can reduce the volume of water reaching the river at any one time and effectively ‘slow the flow’.

Like all changes to land use, Natural Flood Management takes time to mature so we must implement them now. Time is needed both to engage with farmers and landowners and for landscape features like bunded hedgerows to grow. Many of these landscape changes like soil management offer biodiversity improvements and flood risk reductions that the Aire Valley needs now. Storm events are unpredictable. Storm Eva was referred to as a “1-in-200 years flood”, but this doesn’t mean we will have to wait 200 years for another one. Climate change means that heavy rainfall events and becoming more frequent and more severe. In fact, 5 of the 10 wettest years on record have been in the past 25 years and 2024 was the wettest period since record began.

Hard-engineered flood-risk solutions are a vital asset in managing and mitigating flood risk as they can respond to rises and surges in water levels to protect properties, businesses, and key infrastructure. However, these alone cannot provide long term proactive protection against the present and future flood risk facing our communities. Hard-Engineered flood defences need to be supplemented with natural solutions that reduce the impact of flooding to people, businesses, and infrastructure. Natural Flood Management (NFM) involves slowing the flow of water over the land and increasing storage in the catchment to reduce floods. This also benefits the environment by reducing pollution and restoring natural habitats. NFM is a proactive and preventative suite of measures which complement the landscape in which they are located. Not only do they work well with hard engineered defences, but they also reduce wear and tear and therefore maintenance costs.

Natural flood management works with natural processes to reduce flooding. The interventions we will implement have been subjected to peer-review studies and are informed by detailed hydrological modelling of the Aire catchment. The Environment Agency has produced a comprehensive report outlining the impact this can have , indicating the need to use this approach in establishing joined up and holistic flood defence measures moving forward.

As part of Phase 2 of the Leeds Flood Alleviation Scheme (LFAS2), a catchment-wide approach has been developed with the aim of reducing flood risk to Leeds from the River Aire. This includes natural flood management (NFM) measures on the upper and mid stretches of the River Aire as an integral part of LFAS2, complementing planned engineered flood defences in and directly upstream of Leeds city centre. Thomas Mackay Ltd has undertaken hydrological screening of the River Aire and supporting hydraulic and hydrological modelling. The modelling has help prioritise what interventions, and where in the catchment NFM should be focussed to achieve the greatest value and impact.

The hydrological modelling carried out by Thomas Mackay Ltd has been approved by the Environment Agency and underpins ARC’s approach to the delivery of NFM in the upper catchment.

The NFM hub hosted by The Rivers Trust, will act as the asset register for the project and form a key part of the reporting process, enabling access and visibility to stakeholders within the project. The NFM Hub is a tool which allows project managers for catchment-scale or community-led Natural Flood Management (NFM) projects in England to record the information that is relevant to any NFM project delivery, regardless of its size. The NFM Hub allows users to map NFM projects and record relevant evaluation metrics. It is accessible, open source and free to use.

Sadly not. ARC is designed to complement the Leeds FAS, providing long term climate adaption to ensure that when combined, this package of flood defences can provide the level of protection to Leeds necessary to protect against the future equivalent to the Boxing day floods of 2015. However, this kind of work is inherently uncertain, and no set of defences could guarantee total protection against flooding. As with most things, it’s impossible to eliminate risk entirely.

What we can say, however, is that ARC will substantially reduce the risk of flooding in the future. You might think of it in these terms: it will mean that there are many more floods that don’t happen.

ARC is built on extensive hydrological modelling, using data gained from previous severe weather events to best predict the behaviour of water during a future event. This modelling will be regularly updated as throughout the life of ARC to ensure that any adaptations required to maintain effective protection can be implemented.

To give a sense of the impact the Leeds FAS scheme is already having; since 2017, the scheme has already been operated nine times to prevent floods.

So, whilst we can’t guarantee that flooding won’t happen when ARC is up and running, we can say with some confidence that it will mean many more floods don’t happen.

Businesses providing revenue contributions to ARC will sign an agreement with ARC to do so. Within this agreement will be a ‘get out’ clause allowing parties to choose to exit the agreement after the second year under certain circumstances. These conditions are that ARC cannot demonstrate it has secured the full £400k per annum revenue to scale up delivery to ensure the full ambition for the programme or that ARC has not delivered NFM in line with the amount outlined in the agreement.

The NFM will be managed, monitored, and maintained to a high standard on an ongoing basis. The assurance around delivery and maintenance will be a significant part of the contracting process with Buyers and there will be a specific break clause included in case of non-delivery or failure of the measures in place. We are confident in the modelling underpinning the delivery, and of the growing evidence base which supports the impact of NFM in addressing flood risk (see link to Environment Agency report in earlier answer).

Leeds City Council have a wide range of competing priorities around the utilisation of business rates and although ARC should be considered alongside other applications for the funding this generates this will need to be done in future when an appropriate opportunity to review rates is undertaken. Consideration would also need to be given to how this would be tiered or split geographically to represent the influence of flood zones and direct and indirect flood risk and impact, much like the Sheffield based Lower Don Valley Business Improvement District did.

The further into the future that climate modelling is done, the less certainty there is. It is difficult to predict the outcome with certainty due to greater opportunity for developments to occur that could not be predicted or controlled. The climate modelling impact on river flows that informs Leeds FAS provides data up to 2069. This therefore is the future point on which ARC can base its response to climate change. This does not mean ARC will end in 2069. We expect future modelling to take us beyond 2069 to which ARC will respond and continue to protect the city.

Currently, the NFM to be delivered will not directly or immediately influence flood risk banding or consequently the calculation of insurance premiums based on this. However, the impact of the NFM on flood risk will provide increased protection to many businesses and properties. We are engaged with the insurance (and re-insurance) industry to develop the evidence base for NFM’s ability to reduce flood risk which could in the future allow it to influence flood maps and insurance premiums. For this to happen there need to be large scale schemes such as ARC which, in partnership with the hydrological modelling which underpins the scheme can demonstrate its ability to reduce the reach and impact of flooding. This in turn will reduce the volume of insurance claims related to flooding.

ARC will be an independent body, established as a Community Interest Company (CIC). It will consist of a board of directors who share responsibility for the company. Day-to-day programme management will be delegated to a contracted Programme Management role. This body will work on behalf of the board and will engage ARC’s key stakeholders, the Business partners, farmers & landowners, and delivery partners to ensure ARC operates within its remit and delivers its contractual responsibilities.

The board of directors of ARC will represent the key stakeholder groups, for example representatives from the Business and Farmer groups.

The primary benefit achieved by ARC will be flood risk reduction. This benefit will be experienced across all business in Leeds and industry, local communities, and the city region. The impact of flooding stretches far beyond individual incidences of properties flooding; the interconnectedness of business, supply chain and communities mean there is a ripple effect from a flood which impacts supply chains, customers and workforce meaning even businesses not directly flooded will experience a negative impact from floods hitting the city. Beyond flood risk reduction, there are additional benefits to be gained through ARC’s nature-based approach. These include:

Water Quality

Catchment Nutrient Balancing (CNB) is an innovative approach to water company phosphorus permitting which uses integrated catchment planning to address water quality drivers (e.g., Water Framework Directive status). CNB allows water companies to offset the impacts of Wastewater Treatment Works through paying another sector, such as agriculture, to implement measures that go beyond their regulatory fair share. The Environment Agency are the regulator of CNB schemes, and their recommendation is to use the ADAS Farmscoper model to quantify the potential phosphorus savings that can be made on farms. Farmscoper contains over 100 mitigation methods, of which 17 have been agreed for use in CNB in accordance with agricultural fair share. Some of these mitigation methods will align with those delivered through ARC which presents the opportunity to engage with CNB schemes. There may be scope to use additional methodologies for quantifying phosphorus reductions, but these would need to be approved by the regulator.

An alternative approach to the sale of water quality benefits is through the Volumetric Water Benefit Accounting methodology. For further details on this approach please read the Water Stewardship section of the FAQs.

Biodiversity (inc. Biodiversity Net Gain)

The delivery of nature-based solutions through ARC will offer a benefit to biodiversity in the areas it is delivered. Addressing challenges such as climate change through enhancing the landscape and utilising natural processes will ensure greater protection of a varied habitat through which biodiversity can flourish.

Biodiversity Net Gain (BNG) is a policy brought about by the UK Government which aims to create a market for buying and selling Biodiversity Units. The complete guidance and legislation regarding BNG is yet to be released and many questions still surround the policy. ARC will not be engaging with the BNG market in its current form due to the regulatory complexities around stacking BNG with other ecosystem service markets. Additionally, the legislative uncertainties surrounding the policy could pose a risk to the project and create a barrier to landowner engagement due to the 30-year agreements which BNG requires and uncertainties around the tax implications of BNG.

Carbon (inc. Carbon credits)

Although a significant part of the flood protection generated by ARC will be through tree planting, this is being carried out via White Rose Forest who already have systems and buyers in place for the sale of the carbon credits generated through their delivery. Therefore, there is little scope for ARC to offer carbon credits as it will not have access to these.

However, ARC will have a beneficial impact on carbon release in the Aire Valley and Leeds City Centre. We know that floods have a large carbon footprint so ARC itself, through its action in reducing the risk of flooding, will have a positive impact on reducing carbon released because of flooding. A Leeds Council commissioned Edinburgh University study has shown that the embedded carbon of the new flood walls is less than the carbon footprint of another flood like Boxing Day 2015. This would be equivalent to nearly 52,000 tonnes of CO2 being released. This would be equivalent to 3100 return flights from London to New York.

Water Stewardship

The Volumetric Water Benefit Accounting (VWBA) methodology (Reig et al., 2019) allows for the quantification of Volumetric Water Benefits (VWB) delivered through water stewardship activities relative to a unit of time. VWBA uses peer-reviewed methodologies, such as the curve number method, to quantify these benefits. These activities funded through VWBA should address a shared water challenge in the catchment. The Rivers Trust has developed a web tool which uses local data to apply the VWBA methodology, quantifying the volumetric benefits delivered from interventions. These are known as the Replenish benefits and are quantified in m3 per year.

The primary driver of the ARC is to reduce flood risk and therefore interventions will be addressing the shared water challenge of extreme weather events. The benefit of wetlands is quantified as volume stored and the benefit from land use change is quantified as the volume of runoff reduced. There is scope in catchments where there are water quality drivers to quantify the benefit of certain wetlands as volume treated, the methodology assumes that water entering the wetland is failing a recognised water quality standard (e.g., Water Framework Directive) and is observably improved by passing through the feature.

Social Benefits

Natural Flood Management not only provides practical flood risk reduction but also offers a range of social benefits that contribute to the overall well-being and resilience of communities.

The delivery of NFM, through ARC, will involve the creation and restoration of green spaces, wetlands, and other natural features. These areas can enhance the aesthetic value of a community, providing spaces for recreation, relaxation, and connection with nature. Furthermore, the scale and delivery of project will create economic opportunities through job creation and local business development. For example, the restoration of natural areas may require the hiring of local labour contributing to the local economy.

Furthermore, the project will contribute to climate resilience by enhancing a community's ability to adapt to changing weather patterns and increased flood risks. These measures can reduce the vulnerability of communities to the impacts of climate change. The impact and threat of flooding has been well documented to have negative effects on communities. In extreme or recurring situations, it can contribute to poverty and a lack of financial mobility through reduction in property values and difficulties obtaining insurance. The distress created by flooding, or the threat of flooding can cause psychological harm to individuals with long term health consequences. The project will work closely with flood effected community, increasing their knowledge, and understanding of flood risk. This engagement can strengthen community ties, enhance local knowledge, and empower residents to take an active role in managing their environment.