Flood Zones Explained

If you live in England, it may come as a surprise to learn that you are living in a Flood Zone, as defined by the Environment Agency for planning purposes

The Environment Agency has mapped the whole of England according to the annual probability of river and sea flooding

April 20th 2015

The Environment Agency’s definition of Flood Zones is intended for planning purposes and is documented in the Technical Guidance to the National Planning Policy Framework, published in March 2012. [1]

Local Authorities have a statutory duty to produce a Local Plan, which identifies sites that may be suitable for new development. They are also advised to produce a Strategic Flood Risk Assessment, which identifies and maps areas that have a ‘low’, ‘medium, and ‘high’ risk of flooding. The Environment Agency’s Flood Zones are intended to help Local Authorities in this forward planning, the intention being to steer new development away from areas at a high risk of flooding to areas with a lower risk.

The Agency has divided England into four Flood Zones for this purpose, defined as follows:

  • Flood Zone 1 – low probability
  • Flood Zone 2 – medium probability
  • Flood Zone 3a – high probability
  • Flood Zone 3b – the functional floodplain (i.e. land where water has to flow or be stored in times of flood)

It has published a publicly-accessible flood map for planning purposes which uses colour coding to display Flood Zones 2 and 3. Flood Zone 1 is not displayed but includes all the land that falls outside Flood Zones 2 and 3. In other words, everybody in England lives in an Environment Agency Flood Zone, though many will be located in Flood Zone 1 and with a low probability of river and sea flooding. To find out what Flood Zone your site is located in, input your postcode into the map. [2]

Flood Zones and Flood Risk Assessments

The Environment Agency defines an “area at risk of flooding” as being land within Flood Zones 2 and 3, or land in Flood Zone 1 that has critical drainage problems and has been notified as such to the Local Planning Authority. However, “flood risk” means risk from all sources of flooding, not simply river and sea flooding. All sources of flooding would include surface water flooding, groundwater flooding, and flooding from overwhelmed sewers and drainage systems. A Strategic Flood Risk Assessment takes all these sources into account, with the Environment Agency’s Flood Zones making a significant contribution.

A Local Planning Authority uses the Environment Agency’s Flood Zones, together with its Strategic Flood Risk Assessment (if available), to identify if a site-specific flood risk assessment is required when it considers a planning application. The requirements for a Flood Risk Assessment, and the level of detail it should contain, vary according to the Flood Zone a site is located in. In summary:

“A site-specific flood risk assessment is required for proposals of 1 hectare or greater in Flood Zone 1; all proposals for new development (including minor development and change of use) in Flood Zones 2 and 3, or in an area within Flood Zone 1 which has critical drainage problems (as notified to the local planning authority by the Environment Agency); and where proposed development or a change of use to a more vulnerable class may be subject to other sources of flooding.”

The Environment Agency’s designation of Flood Zones is also a factor in determining whether a proposed development is appropriate for the Flood Zone it is located in. With this end in mind, it has classified land use according to ‘Flood Risk Vulnerability’, the uses ranging from “water compatible development” (such as flood control infrastructure), through “less vulnerable”, “more vulnerable” and “highly vulnerable” uses, to “essential infrastructure.” A Local Planning Authority uses this classification not only as a guide to decide whether a proposed development is appropriate for its Flood Zone area, but also to decide what level of detail a Flood Risk Assessment should contain. For example, ‘less vulnerable’ uses (which include buildings used as shops, restaurants or offices) generally require less detail than ‘highly vulnerable’ uses (which include basement dwellings, mobile homes, and police and fire stations).

The conclusion from all of the above is that there is no “one size fits all” when it comes to assessing flood risk. The government’s planning portal website states that a site-specific flood risk assessment should always be proportionate to the degree of flood risk. A flood risk assessment should also be appropriate to the scale, nature and location of the property or development. [3]


[1] Technical Guidance to the National Planning Policy Framework, containing the Environment Agency’s definition of Flood Zones, is available as a PDF document from the GOV.UK website.

[2] Flood Zones are based on the annual probability of river and sea flooding, ignoring the presence of defences. For example, it is unlikely, but possible, that a flood with an annual probability of 1% will occur two years running. The definitions are set out in the National Planning Policy Guidance, as follows:

  • Flood Zone 1 – Land assessed as having a less than 1 in 1,000 annual probability of river or sea flooding (< 0.1%) in any year.
  • Flood Zone 2 – Land assessed as having between a 1 in 100 and 1 in 1,000 annual probability of river flooding (0.1% – 1%), or between a 1 in 200 and 1 in 1,000 annual probability of sea flooding (0.5% – 0.1%) in any year.
  • Flood Zone 3 – Land assessed as having a 1 in 100 or greater annual probability of river flooding (> 1%), or a 1 in 200 or greater annual probability of flooding from the sea (> 0.5%) in any year.

[3] For a more detailed explanation of Flood Zones, see our web page “Do I live in a Flood Zone?”.


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Ford near Clun © Copyright Anthony Bloor and licensed for reuse under a Creative Commons Attribution-ShareAlike 4.0 International License.

‘International Year of Soils 2015’ highlights importance of soil

The Food and Agriculture Organization is promoting a number of events to raise awareness of soil’s importance for human health, ecosystems and food security

April 17th 2015

2015 has been designated as the ‘International Year of Soils’ by the United Nations, following a declaration of its 68th General Assembly held in 2013. The Food and Agriculture Organization of the UN has been nominated to implement the aims of International Year of Soils 2015 and will be promoting a number of events throughout the year intended to raise awareness of the importance of soil for essential ecosystem functions and food security.

The Food and Agriculture Organization (FAO) says that the specific objectives of International Year of Soils 2015 are to:

  • Raise full awareness among civil society and decision makers about the profound importance of soil for human life
  • Educate the public about the crucial role soil plays in food security, climate change adaptation and mitigation, essential ecosystem services, poverty alleviation and sustainable development
  • Promote investment in sustainable soil management activities that will develop and maintain healthy soils for different land users and population groups
  • Advocate for rapid capacity enhancement for soil information collection and monitoring at all levels (global, national and regional)
  • Support effective policies and actions for the sustainable management and protection of soil resources
  • Strengthen initiatives in connection with the United Nation’s ‘Sustainable Development Goals’ process and post-2015 agenda

The importance of soil for food security is based on the estimate that 95% of our food is directly or indirectly produced on our soils. Because food availability relies on our soils, healthy and good quality food can only be produced if our soils are healthy. “A healthy living soil is a crucial ally to food security and nutrition,” says the FAO.

Whether a soil is healthy or not depends on its capacity to function as a living system. The FAO says that healthy soils maintain a diverse community of soil organisms which provide a multitude of ecosystem services, including the breakdown of waste and pollutants, the recycling of essential plant nutrients, and helping to prevent groundwater and surface water pollution. A healthy soil also contributes to the mitigation of climate change by maintaining or increasing its organic carbon content.

However, it is estimated that approximately 33% of our soils are facing moderate to severe degradation and the FAO says that the current rate of soil degradation threatens the capacity to meet the needs of future generations, unless this trend is reversed by a concerted effort towards the sustainable management of soils.

Soil degradation refers to a reduction in the capacity of soil to function as a living system. Soil degradation can take a number of forms including soil erosion, soil salinisation, nutrient depletion, a loss of soil biodiversity, soil pollution, soil compaction, and the loss of organic matter. On agricultural land, one consequence of soil degradation is an increased risk of flooding. A study by the Environment Agency found that about 90% of agricultural soils in the South-West of England suffer from poor structure whilst about 40% are badly compacted, causing surface water run-off and soil erosion across entire fields – see our news item “Farmers advised on how to reduce flood risk”.

Soil is considered to be a non-renewable resource because it does not renew itself at a sufficient rate in the human time frame. One centimetre of soil, says the FAO, can take hundreds to thousands of years to form from parent rock. But the FAO argues that soils have been taken for granted for a long time whilst human pressures on soils are reaching critical limits. Consequently, “there is an urgent need to raise awareness of the importance of this strategic resource.” For more information on International Year of Soils 2015, see the Food and Agriculture Organization website.


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Menhir in a field near St Buryan, Penwith, Cornwall © Copyright Anthony Bloor and licensed for reuse under a Creative Commons Attribution-ShareAlike 4.0 International License.

Big City Plan for Birmingham attracts £378m in local growth funding

Snow Hill redevelopment is Birmingham’s answer to Canary Wharf

Plans to create new office space and 4,000 new homes

April 13th 2015

Birmingham City Council announced plans earlier this year to regenerate the Snow Hill area as part of its strategy to attract more businesses to the city centre. The plans include better transport links, improved public spaces, and other work designed to attract property developers, financial businesses, and investors in infrastructure. Birmingham’s Big City Plan was set out in 2010 and the latest proposal was unveiled in January, following a deal with central government which will add a further £21.4 million to the current £357 million in local growth funding. The latest proposal is for a mixture of public and private funding to fund a twenty-year programme of improvements.

Speaking to the Telegraph, Sir Albert Bore, the leader of Birmingham City Council, said it was the right time to propose the redevelopment of Snow Hill. “Because of the way that the economy is going in Birmingham, we’ve now got to the point where by the end of 2015 there will be no grade A office space available. We have to take advantage of a steady stream of business enquiries in the city,” he said, and added that there was substantial interest in the proposal from developers and possible tenants.

Birmingham has a designated enterprise zone in the city centre, which includes Snow Hill. The enterprise zone allows the area’s local enterprise partnership to offer discounted business rates and easier planning rules for property development. According to the Telegraph, the Snow Hill ‘master plan’ is expected to create an additional 200,000 square metres of new office space, up to 4,000 new homes, and 10,000 jobs. The Council has claimed that the scheme will be Birmingham’s answer to Canary Wharf, but with operating costs 55% lower than in London. One of the existing office blocks at Snow Hill is expected to house the headquarters of HS2, the high speed rail link planned to connect London to Birmingham by 2026.

Sir Albert Bore said that cuts to local authorities were affecting the Council’s ability to deliver core services, but “on the other side of the coin, we can bring in investment to provide us with some means of ensuring in the future that jobs will be there. It’s two different pots, and they don’t harmoniously sit together. It’s hard for people to understand that we are investing on one hand but cutting services on the other – but we are using financial tools that are not available on the other side.”


Birmingham’s New Street station is also going through a process of redevelopment. © Copyright Anthony Bloor and licensed for reuse under this Creative Commons License.

Thames Water sets out plans to tackle sewer flooding

London’s sewer network struggling to cope with demands

April 6th 2015

Thames Water has announced it has invested £346 million to reduce the risk of sewer flooding for 2,500 properties in the Greater London area by 2015. The investment is focused on reducing the risk of flooding to properties which have already suffered internal flooding and its plans include the building of underground tanks to collect and store heavy rainfall, increasing the capacity of its sewers, and offering flood mitigation to homes at risk.

London’s sewer network was built in the 1800s but the city has since trebled in size and the sewer network is struggling to cope. Thames Water says: “More intense storms resulting from climate change, increased housing development and the paving over of green spaces to provide off-road parking, are all increasing the amount of surface water entering our sewer network. This, combined with people disposing of inappropriate waste into our sewers, is contributing to an increased risk of sewers flooding homes and properties.”

Sewer Surveys

Ofwat has set two targets for Thames Water: firstly, for a 10% reduction in annual instances of properties being affected by internal sewer flooding; and secondly, for a 9% reduction in leakage levels. As part of its strategy to reach the first target, Thames Water is in the process of carrying out surveys in areas of sewer problems to check whether the cause is a blockage or a sewer collapse. The surveys will involve camera investigations, water jetting the sewers, and mapping their location. The water company says the surveys will help to improve the network of sewer pipes in its region: “This will help reduce blockages and the need for future repairs. This programme of work is one of the largest we have ever undertaken for our sewer network and will involve checking the condition of the private sewers that came under our ownership in 2011.”

Counters Creek Flood Alleviation Scheme

Thames Water has been working on a range of measures to further reduce the risk of sewer flooding. Since 2010, the company has fitted 700 non-return valves on properties to stop sewage backing up through their pipes. A further 600 will be installed over the next six years. Thames Water also held a consultation recently on plans for a flood alleviation scheme for the Royal Boroughs of Hammersmith & Fulham and Kensington & Chelsea. The company says the Counters Creek flood alleviation scheme aims to reduce the risk of sewer flooding to over 1,700 basement properties in the two boroughs. The scheme will involve the construction of a new storm relief sewer, local sewer improvements, and trials of sustainable drainage systems and other measures to protect individual properties, such as anti-flooding (FLIP) devices. The consultation focused on how and where the new storm relief sewer will be constructed.

Water Briefing says 1,700 homes and businesses have flooded in recent years across the two boroughs, and more than a thousand properties are threatened by heavy rain “which overwhelms drains and sewers, forcing sewage to back-up in the pipes and overspill out of toilets and sinks.” Water Briefing also says that Thames Water set up an Independent Advisory Group comprising three leading academics in the field of urban drainage to review and challenge its plans as they developed. A Thames Water study revealed the urbanisation of London has contributed to the area’s problems, with impermeable land, which stops rainwater filtering through soil, increasing in the Counters Creek area by around 17% since 1971.


Thames Water came under scrutiny recently from the London Assembly’s Environment Committee, following an incident in which more than 1,000 trains were cancelled or delayed due to a burst water main near Farringdon station. Richard Aylard, External Affairs and Sustainability Director for Thames Water, told the Committee that the company was “pushing hard” for a national policy statement by the Government for water, saying that a national policy would give a boost to the sector to get infrastructure and resource projects “fast-tracked” through the planning system. He also said that Thames Water has a protocol in place with London Underground and that a similar principle with Network Rail should be set up. He was also asked about the likely increase in water bills due to the estimated £4 billion cost of the proposed ‘super sewer,’ the Thames Tideway Tunnel. Water Briefing reports that the cost is predicted to be around £34 per Londoner per year by 2020.

Groundwater Flood Risk & Sewer Flooding

Mark Fermor, Managing Director of the environmental consultancy ESI Ltd, is a hydrogeologist with a particular expertise in groundwater. He says that ESI’s ground-breaking Groundwater Flood Risk Map has helped water companies and waste water service providers reduce the risk of sewer flooding. “Although emergent groundwater tends to be clear and relatively clean compared to muddy fluvial flood waters, it has the potential to be contaminated by sewers and brownfield sites,” says Mark, “and it is the discharge of untreated sewage effluent during storm events that forms one of the primary mechanisms causing pollution of surface waters in England and Wales.” Mark explains that such discharges can occur when the flow entering works exceeds the treatment capacity or when storm overflows in the sewer system become active to prevent the network capacity being exceeded. “Under such conditions,” he says, “flows in the sewer networks can be significantly increased when the water table rises above the sewer invert level through defects in the system that allow the ingress of groundwater.”

ESI’s Groundwater Flood Risk Map has identified that the areas at risk from groundwater flooding are considerably less than previously flagged by others, and it allows the user to get a large-scale understanding of the groundwater flood risks of a region and an indication of the potential flood risks at a given site. The map has improved and expanded existing data by introducing the probability of a flood event, based on the 1 in 200 year groundwater levels – i.e. a 0.5% annual probability of a flood event – and on the severity of the flood event. The map is a powerful screening tool when planning major infrastructure projects, allowing water companies to better understand the areas of most pressing need for remediation works for instance. For more information, see the ESI website.

Wales Water Conference – ‘Wales Water 2015’

Wales Water Conference will examine the new Water Strategy for Wales

April 2nd 2015

The UK water industry’s leading publication Water and Wastewater Treatment (WWT) has organised a one-day conference for water professionals and environmentalists to be held in Cardiff on May 20th. ‘Wales Water 2015’ will bring together representatives from central and local government, water utilities, contractors, environmental and economic regulators, NGOs and consumer bodies.

WWT says the aim of the conference is to examine the new Water Strategy for Wales and the current and future pressures facing the sector: “The conference will examine the progress towards a joined-up approach to managing natural resources in Wales, and bring a number of stakeholders together to discuss strategies to reduce diffuse pollution. The 2015 event also features three new interactive workshops focusing on innovative highland, lowland and coastal water related projects.”

The conference features two morning sessions – ‘Water Strategy and Guidance’ followed by ‘Natural Resource Management’ – whilst the afternoon sessions feature three interactive workshops followed by ‘Innovation in Action,’ which includes presentations on ‘Delivering innovation in AMP6’ and ‘Catchment management innovation.’ There will be a broad range of speakers, including representatives from the Welsh Government, Ofwat, Dwr Cymru (Welsh Water), Natural Resources Wales, the NFU, the Centre for Ecology & Hydrology, and environmental experts from the Welsh universities.

Among the topics to be discussed are:

  • The new Water Strategy for Wales
  • Customer trust and confidence in water and waste water services in Wales
  • Progress towards a joined-up approach to managing our natural resources
  • Land use mapping and its importance in planning interventions
  • Catchment management innovation
  • Tackling diffuse pollution

‘Wales Water’ is an annual event. For the latest news, see the conference website at “Wales Water”.


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Llyn Llygad Rheidol © Copyright Anthony Bloor and licensed for reuse under a Creative Commons Attribution-ShareAlike 4.0 International License.