Answers to commonly-asked questions about Flood Map.
1. What is the Flood Map?
The Flood Map is a multi-layered map which provides information on flooding from rivers and the sea for England and Wales. The Flood Map also has information on flood defences and the areas benefiting from those flood defences.
2. What does it show?
The key for the Flood Map consists of the following layers of information:
- Flooding from rivers or sea without defences - the natural flood plain area that could be affected in the event of flooding from rivers and the sea
- For flooding from rivers the map indicates the extent of a flood with a 1% (1 in 100) or greater chance of happening each year
- For flooding from the sea the map shows the extent of a flood with a 0.5% (1 in 200) or greater chance of happening each year
- Extent of extreme flood - the extent of a flood with a 0.1% (1 in 1000) or greater chance of happening each year
- Flood defences - flood defences such as embankments and walls, and flood storage areas (which are areas of land designed and operated to store flood water)
- Areas benefiting from flood defences - where possible we show the areas that benefit from the flood defences shown, in the event of a river flood with a 1% (1 in 100) chance of happening each year, or a flood from the sea with a 0.5% (1 in 200) chance of happening each year. If the defences were not there, these areas would flood. Note that we do not show all areas that benefit from flood defences.
- Main rivers - these are usually larger streams and rivers. Our powers to carry out flood defence works apply to main rivers only. In England, Defra decides which are the main rivers. The Welsh Assembly Government does this in Wales.
The Flood Map does not provide information on flood depth, speed or volume of flow. It doesn't show flooding from other sources, such as groundwater, direct runoff from fields, or overflowing sewers. Your local Environment Agency office may have more information on these. Call 0370 8506506 to find out who to contact at your local office.
3. How was the Flood Map produced?
The Flood Map combines detailed local data from modelling and mapping studies with information from a national model of England and Wales.
For rivers, detailed survey data gives us information about the topography or ground surface, and we combine this with information on flows. For coastal areas, we again take detailed survey data and combine it with analysed sea level and wave data. This allows us to work out the water level at the coast and how the water could flood inland. Where detailed mapping is not available, we have supplemented our data with national generalised modelling, which gives a consistent picture of flood risk for all rivers with a catchment size greater than 3 km2 and the sea.
4. Who uses the Flood Map and why?
The Flood Map is designed to increase awareness among the public, local authorities and other organisations of the likelihood of flooding, and to encourage people living and working in areas prone to flooding to find out more and take appropriate action.
The Flood Map can also be used by those people who wish to apply for planning permission in England to see whether the site they plan to develop is in a flood risk area.
To assist householders and insurers in providing insurance, we have supplied ABI member insurance companies with information that gives a national assessment of likelihood of flooding from rivers and the sea, within the floodplain taking into account flood defences. It provides a first step for insurers in assessing flood risk for a general location and forms part of a wider range of information that they use in their risk assessment.
5. Is the Flood Map ever updated?
As further appropriate information becomes available, it is included in quarterly updates to the published Flood Map. These updates take place in January, April, July and October. Flood defences not yet shown are added gradually through these quarterly updates.
6. Why do you need to update the map?
We are committed to provide the best latest information to the public on flood risk. Our models are predictive and in the event of actual flooding we need to revise the maps to take account of the new information received.
We also have an ongoing programme of improvement; as more detailed models are developed, and we have access to more information, we update the maps with it.
7. How accurate is the data?
Flood mapping is a complex, detailed and extensive process which can never be completely accurate, but we will always provide the best currently available information, using national consistent data. The Flood Map gives a good indication of the areas at risk of flooding in England and Wales. However it cannot provide detail on individual properties.
8. I thought that I was protected by a flood defence but it isn't shown on your map
Not all defences and areas that benefit from flood defences are shown yet. More are being added as part of the updating process. We also undertake a lot of maintenance and clearance to our rivers, to reduce the chance of flooding, but there isn’t room to show all of this on the Flood Map.
9. What do you mean by likelihood of flooding?
The probability or likelihood of flooding is described as the chance that a location will flood in any one year. The likelihood is expressed as a percentage i.e. 1%, or as a chance expressed for example as 1 in 100 chance in any given year. It is important to remember that the risk of a flood occurring is there at all times - this year, next year and future years.
10. How do I find out whether I can insure my home for flooding?
Insurance companies decide whether to offer flood insurance to properties. However, an agreement reached between the Association of British Insurers (ABI) and Government in 2002, and updated in 2005 and 2008, known as the ABI Statement of Principles, means that insurance companies offer insurance to many properties that are at risk of flooding.
The Environment Agency has helped to ensure that as many people as possible are able to obtain insurance by providing information on the risk of flooding across the whole of England and Wales from a National Flood Risk Assessment. This is a snapshot of flood risk at a national scale taken in 2008. The information from this assessment is provided on the website to support the Flood Map. By clicking within either of the blue areas of floodplain, you can see which of three further categories of likelihood of flooding (significant, moderate, or low) apply there. These categories are based upon the likelihood of flooding from rivers and the sea at a location, taking into account the presence and effect of flood defences. As it is a national assessment, it is not able to state what the actual likelihood of flooding is to any specific property.
11. Will my insurer use the Flood Map?
Insurers have been given the same information on flood risk as you can access on the Internet by clicking within either of the blue areas of floodplain. None of our flood mapping shows the risk at a particular property as we carry out flood mapping for areas of land. This is because we cannot know all details about all properties, for example how high the floor level is above ground level. Insurers can therefore only use the information as a first stage in assessing the flood risk for a general location.
12. What if there are any errors in the data? Will it affect my house insurance?
The National Flood Risk Assessment gives us an indication, at a national level, of the likelihood of areas of land flooding.
Using the latest science, which is developing all the time, lots of different data is modelled to give an overview of where flooding is most likely across the country. It does not specifically tell us which properties will flood, but gives us a good indication of land areas that could flood.
However, as it uses vast quantities of data, from across many different datasets for England and Wales, there are some errors which although they do not affect the national overview, they can affect the local flood risk picture. As we develop NaFRA we will be improving the data to correct these errors.
All the companies (including insurers) who use NaFRA data have been told that it is indicative only. It should not be used in isolation to make decisions about local flood risk. There are various ways to check data, including contacting our area offices directly to get the latest flood risk information, from the most recent studies. We have agreed with the insurance industry that property owners can contact us to check their flood risk. If the national data does not reflect the local situation accurately, we will give them a letter with the most recent local flood risk data to send to their insurers.
We are already working on how NaFRA will be developed in the future, to give an even more comprehensive picture of flood risk.
13. How has the likelihood of flooding been calculated and does it take account of climate change?
The likelihood of flooding has been calculated using predicted water levels and taking the location, type and condition of any flood defences into account, whether or not they are currently shown on the Flood Map.
NaFRA is an assessment of flood risk based on information last updated in 2008. It shows the likelihood and consequences of flooding that could happen now. It does consider climate changes that have already happened but it does not show how the risks will increase in the future due to climate change. However, we are planning to develop and use this method to determine how flood likelihood may change in the future with climate change.
It is worth bearing in mind that the potential extent of an extreme flood shown on the Flood Map might in future become more 'normal' as a result of climate change.
14. Why is there no information on the likelihood of flooding for my area?
The method for calculating the likelihood of flooding is independent of the method for calculating flood extents. The likelihood calculations are more complex and require more detailed input datasets. For a very small number of locations, this extra data was not available at the time of production of the likelihood of flooding. We are continually improving and updating the data and will be reducing the areas where there is no information.
15. Why does clicking within either of the blue areas of floodplain tell me that my area is outside the extent of an extreme flood, when the map shows my area clearly in the floodplain?
The information accessed through clicking within either of the blue areas of floodplain is a snapshot of flood likelihood, at a national scale. There are two possible reasons why it may tell you that you are outside the extent of an extreme flood when the map shows your area in the floodplain. One possible reason is that the area you are looking at falls in or within three metres of a river, estuary or sea. In this case you may wish to try clicking slightly further away.
The second possible reason is that we have updated the mapped extent of extreme flood - which we will do every three months if we have better information - but have not yet updated the assessment of likelihood of flooding.
16. Why does an area behind a defence still have a 'significant' or 'moderate' flood likelihood?
Flood defences do not completely remove the risk of flooding, but they do reduce it. Defences are built to withstand a flood of a certain magnitude but can be overtopped or fail either in extreme weather conditions or due to poor condition. Defences are built to different design standards according to local needs. Information on the likelihood of flooding takes account of the condition of defences as well as the standard of protection they provide. Your local Environment Agency office may be able to provide more information on the defences in your area. Call 0370 8506506 to find out who to contact in your local office.
17. Why does the flood probability data occasionally indicate a significant risk for locations within the light blue shaded area?
The flood extents shown on the Flood Map and the flood probability data accessible by clicking within either of the blue areas of floodplain have been calculated using two different and independent methods. The flood probability data takes account of defences which could be breached or fail in a major event.
18. Does your latest flood risk assessment show that flood risk is increasing each year?
The NaFRA will eventually enable us to monitor flood risk each year to determine whether it is increasing as a result of climate change, further development in floodplains and/or as a result of deteriorating condition of existing flood defences. But the assessment needs some further improvements before we can use it for this purpose.
As this is only the fourth time the NaFRA for England and Wales has been undertaken we are not able to see a trend in the results to be able to answer this question. However, as future assessments are completed it is expected that we will see a trend in the level of flood risk.
These assessments are expected to show that flood risk is increasing. What we want to find out is by how much and the level of funding that may be necessary if we choose to hold the risk at the current level or choose to reduce the risk.
All of our decisions in managing flood risk will be based on appropriate flood risk assessments so we can ensure that our actions will maximise the return on investment measured by the reduction in flood risk. It is important that our flood risk assessments links with those undertaken by others (e.g. the spatial planning system) to ensure that planning decisions do not put more lives or property at risk.
19. What's included in the assessment and what isn't?
The NaFRA includes flooding from all rivers with a catchment size greater than 3 km2, and all flooding from the sea (both along the open coast and tidal estuaries). Smaller rivers are included in the assessment where they fall within the area that could be affected by an extreme flood (0.1% chance in any year). It does not include other forms of flooding such as from highway drains, sewers, overland flow or rising groundwater.
The assessment takes into account the type, location and condition of flood defences.
20. Why aren't you including other forms of flooding in your data, as well as flooding from rivers and the sea?
The NaFRA has been developed with the potential to enable us to include other forms of flooding in our flood risk assessments in the future. However, we need to make sure that we have appropriate methods to assess that risk, that we understand the uncertainty associated with the results. Following on from the review of the Summer 2007 flooding we have been approaching local resilience forum partners (e.g. local authorities, water companies etc) to gather data from other types of flooding to feed into a national database. We can then use that data to help validate and improve future flood risk assessments.
21. I don't agree with the map for my area. I want to challenge your information
If you believe that a particular location is not at risk of flooding, or if you have information that you believe we may not have taken into account, please contact your local Environment Agency office, who will consider your comments and will advise on the appropriate procedure. However we would be unlikely to be able to consider an amendment to the Flood Map based only on anecdotal evidence.
22. My property has never been shown as being in the floodplain before but it is now, why is this?
We are committed to provide the best information to the public on flood risk. New data from local studies is continually becoming available and is used to update the Flood Map quarterly, to make sure that the most up to date information is available. This means that some areas which we did not previously know were at risk of flooding are now known to be at risk; in other areas, our more detailed understanding of flood risk areas means that we have reduced the extents shown on the Flood Map.
23. Is a flood warning service available to me?
By using the link on the Flood Map, you will be able to find out whether you can get an advance flood warning.
24. I've lived in my village for 50 years and I know this property has never flooded. Why is it shown on your Flood Map?
A flood with a 1% (1 in 100) or 0.1% (1 in1000) chance of happening in any one year may well not occur within the space of 50 years. Being in a floodplain doesn't mean your home or business will definitely be flooded - many other factors come into the equation. The maps are a guide and should prompt people who live near a river or the sea to be aware and find out more.
25. I don't live near a river or the sea, why am I shown on your Flood Map?
Flood flows follow the natural contours of the ground - therefore the area that may flood could be some distance from a river. The location may be on a route that floodwater will take. Alternatively there may be culverted watercourses under the property or nearby, which you may not be aware of - during a flood these may not be able to carry all of the flood flow, and some water will flow above ground.
Flooding can occur from other sources such as groundwater and surface water runoff, but flooding from these sources is not shown on our map.
26. How do I get a copy of the Flood Map?
You can request a printed copy for your location, for your personal use, by contacting your local Agency Office, or by calling our National Customer Contact Service on 0370 8506506 or email@example.com. There is a charge associated with re-use of electronic data, or with data for commercial or business use. A licence for this purpose can be supplied by the Information Enterprise Centre: firstname.lastname@example.org