Useful Information (FAQ)

Flood risk modelling uses computer simulations to predict how water will flow and cause flooding, based on factors like terrain, rainfall, and river levels. It is used to assess and manage flood risk by creating flood maps, planning flood resilience projects, guiding development decisions, and preparing emergency response plans.  

It is important to bear in mind that: 

Yes. The model of the river that was developed by the River Thames Scheme (RTS) is the basis for the West London Communities Project (WLCP) modelling. Additional scenarios were added to show the impact of the change in Thames Barrier operation.

The same team of modelling experts worked on the WLCP modelling and the RTS modelling to ensure continuity of approach. 

The models went through extensive quality assurance. The model results were verified and calibrated against real world events from the decades of gauging history we hold for the River Thames. 

The results we have presented follow a standard approach which we use for other flood risk models across the country. The results show the peak water level for that event, i.e. the peak of the high tide coinciding with the peak river levels. While the background model contains more detail, the results only show the maximum water levels we expect to see during different flood scenarios.

Therefore, the variation in water levels which communities experience between low and high tides is not represented in the model results. This does not mean that tides have not been accounted for in the modelling. The results just show the peak water level when high river levels coincide with the peak of the high tide. This allows us to plan for worst case scenarios under different river and tide conditions, and ensures that any interventions to manage flood risk account for peak water levels. All the results we have presented are a combination river levels and tide levels.

The risk of flooding is increasing across the country due to a changing climate, causing more frequent and intense rainfall events and storms, as well as sea level rise.

Communities from Richmond up to Sunbury, grouped as West London communities in this project, already face the growing threat of flooding from multiple sources which will continue to rise with climate change. Sea level rise and more extreme rainfall patterns will progressively increase flood levels in these communities, impacting up to 4,000 residential and commercial properties.

The most severe flooding often results from combinations of flooding, such as high river levels coinciding with periods of intense rainfall and high tides. Like most urban areas, this area is also vulnerable to surface water flooding (flooding from overland flow of rainfall). The risk of surface water flooding is projected to rise because of increased rainfall intensities resulting from climate change.

We know that the Lower River Thames is slow to rise and fall, so properties and businesses can remain flooded for days or even weeks. We will consider this when we start investigating future resilience measures.

We will continue work with professional partners to manage future flood risk and support communities to be resilient to flooding.

The West London Communities Project will focus specifically on flood resilience measures for properties and critical infrastructure such as transport, hospitals and schools. The project itself will not look at flood resilience for public spaces, the Thames Path or moorings.

However, we will share the modelling data with the Thames Landscape Strategy Partnership and help them understand how to use it to inform their refresh of the Strategy as part of the Joint Thames Strategy project.

When we share this data with our other external stakeholders, we will also encourage them to consider how this will affect their own operations and assets, and to make plans to adapt accordingly.

No. As part of the Thames Estuary 2100 Plan we are considering possible options for flood storage areas downstream of the Thames Barrier, but not in South-West London or Surrey. However, it’s important to note that many open spaces adjoining the Thames in these locations will see increasing flood depths and extents because they are part of the floodplain. 

For example, Syon Park, Old Deer Park and Petersham Meadows all have large areas on the riverward side of the flood defences. We recognise that undefended floodplain, where present, will play an important role as a buffer to the impacts of climate change.

To help communities adapt to climate change while accepting that some flooding is unavoidable, the West London Communities Project will be looking at small scale, local measures to improve resilience to flooding for properties, such as:

The River Thames Scheme (RTS) focuses exclusively on fluvial flood risk upstream of Teddington Weir. We are jointly delivering RTS with Surrey County Council.

The Thames Estuary 2100 Plan focuses primarily on tidal flood risk downstream of Teddington. The West London Communities Project is part of the Thames Estuary 2100 Plan and will investigate and deliver flood risk management measures to mitigate the change in risk for communities in South-West London and Surrey that will be affected by changes to operating the Thames Barrier from 2035.

No. To progress and secure funding, each scheme needs to demonstrate it won’t cause flooding elsewhere. Flood Risk Assessments are carried out along with investigations on the scheme’s potential impact on river flows, sediment movements and other issues which can impact the river and flood risk.

We consider the interaction of all the schemes in the River Thames as a whole, including the system of locks and weirs in the non-tidal part of the river. This ensures flood water is managed and controlled and doesn’t cause problems downstream.

Closing the Thames Barrier is one of the ways the Environment Agency currently manages flood risk in South-West London and Surrey. By shutting out the incoming tide, the closure of the barrier helps to increase the capacity in the Thames and its tributaries, reducing the impact of river flooding between Richmond and Sunbury. 

Climate change is bringing more extreme weather, flooding, and frequent intense storm surges from the North Sea. This will increase the number of times the Barrier needs to close and put significant pressure on its operation. So, from 2035, we will adapt how we use the Thames Barrier to help protect London from these growing risks.

Like all infrastructure, the Thames Barrier requires regular inspection and maintenance to ensure it is reliable and can close when needed. Frequent barrier closures limit the time available for maintenance, which may reduce its reliability. Closures can also disrupt navigation and reduce upstream water quality.

The Thames Estuary 2100 Plan sets a threshold of 50 closures per year on average for the Thames Barrier. This threshold is for strategic planning to set deadlines for changes to the defence system, including upgrading and raising defences. We will close the Barrier more than 50 times in a year if required.

Limiting the number of times we operate the Barrier, alongside increased maintenance and repairs, means it can continue to protect London up to 2070, when a replacement will be needed.

Yes, we will close the Thames Barrier for big fluvial events if they combine with high tides with the potential to overtop walls and embankments in central London. This is in line with the Thames Estuary 2100 Plan approach to continue using the Thames Barrier to manage flooding in defended areas between Teddington and Charlton.

Changing how we use the Thames Barrier in 2035 is an action in the Thames Estuary 2100 Plan. The Plan pioneers an adaptive management approach to address the challenge of rising sea levels on the Thames Estuary and the growing threat of tidal flooding.

This change is outlined in the Thames Estuary 2100 Plan, which was first published in 2012 following wide consultation with communities, stakeholders and government, including HMT approval. The Thames Estuary 2100 Plan was subsequently reviewed and updated in 2023.

Maintaining the Thames Barrier is a key part of keeping it reliable. We have a dedicated, full-time team that conducts test closures to exercise the gates and train staff, performs regular engineering assessments, carries out preventative maintenance, and delivers upgrade and replacement projects.

In addition to changing Barrier operation in 2035, we will also be taking other measures to keep limit the number of closures. We will be improving the accuracy of tidal forecasting to reduce the number of precautionary closures. And increasing the height of the tidal flood walls and embankments upstream of the Thames Barrier by 2050 and 2090, allowing higher tides to pass into Central London.

Yes, we will no longer use the Thames Barrier to manage flooding upstream of Teddington from 2035. We have made this decision using the best available evidence and data for sea level rise and tidal variations, and the latest Thames Barrier operation modelling.

The government approved and published the Thames Estuary 2100 Plan in 2012 after two rounds of public consultations with partners and communities. The evidence base of the Thames Estuary 2100 Plan was recently reviewed in 2023, which confirmed 2035 is the latest date we can change Thames Barrier operation and continue to safely maintain the asset.

We cannot eliminate all flood risk. We all have a role to play in making ourselves and our homes and businesses more resilient to the current and growing threat from flooding. 

With flood risk expected to increase in the future, there are things we can all do to make ourselves ready. Essential first steps are:

1. checking your flood risk,
2. signing up for flood warnings, and
3. making a flood plan.

Making our homes and businesses more flood resilient is a vital part of responding to the climate emergency.

People should also consider property flood resilience (PFR) measures, with the aim of making homes more resilient to flooding and make it easier to recover following flood events.

PFR can include measures such as air brick covers, water resistant doors and non-return valves on drainage. These measures will make houses more resistant to flood water but will not stop it entering entirely during floods that last a long time.