The information on the Flood Map for Planning (Rivers and Sea) is designed to only give an indication of flood risk to an area of land and is not sufficiently detailed to show whether an individual property is at risk of flooding. This is because we cannot know all the details about each property.

The Flood Map for Planning (Rivers and Sea) 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.

The Flood Map for Planning (Rivers and Sea) only shows the predicted likelihood of flooding from rivers or the sea for defined areas, and is not detailed enough to account for precise addresses. Individual properties therefore may not always face the same chance of flooding as the areas that surround them.

Flooding has the same chance of happening in any year, with smaller floods happening more often than bigger floods.

Flood Zone 2 - medium probability

These areas have been shown to have between 0.1% – 1% chance of flooding from rivers in any year or between 0.1% – 0.5% chance of flooding from the sea in any year.

Flood Zone 3a - high probability

These areas have been shown to have a greater than 1% chance of flooding from rivers in any year or greater than 0.5% chance of flooding from the sea in any year.

Flood Zone 3b - the functional floodplain

There areas are what are called the functional floodplain. This is at most risk from flooding from rivers or the sea. This land has a 5% or 1 in 20 chance of flooding and is where water is stored when a flood occurs.

Source: https://environment.data.gov.uk/dataset/86ec354f-d465-11e4-b09e-f0def148f590

The Environment Agency's (EA) Spatial Flood defences layer is a comprehensive and up-to-date dataset in England that shows flood defences currently owned, managed or inspected by the EA.

Flood defences can be structures, buildings or parts of buildings. Typically these are earth banks, stone and concrete walls, or sheet-piling that is used to prevent or control the extent of flooding.

A defence is any asset that provides flood defence or coastal protection functions. This includes both man-made and natural defences. Natural defences may include man-made elements to make them more effective or protect them from erosion. Normally a number of assets will be used together to manage the risk in a particular area, working in combination within a risk management system.

Source: https://environment.data.gov .uk/dataset/8e5be50f-d465-11e4-ba9a-f0def148f590

Source: © Copyright Colin Smith and licensed for reuse under Creative Commons Licence.

The dataset shows the chance of flooding from rivers and/or the sea, based on cells of 50m. Each cell is allocated one of four flood risk categories, taking into account flood defences and their condition. No more detailed resolution is provided.

The four categories are shaded in different colours of blue and explained in more detail below.

High risk means that this area has a chance of flooding of greater than 3.3% each year. This takes into account the effect of any flood defences in the area. These defences reduce but do not completely stop the chance of flooding as they can be overtopped, or fail.

Medium risk means that this area has a chance of flooding of between 1% and 3.3% each year. This takes into account the effect of any flood defences in the area. These defences reduce but do not completely stop the chance of flooding as they can be overtopped, or fail.

Low risk means that this area has a chance of flooding of between 0.1% and 1% each year. This takes into account the effect of any flood defences in the area. These defences reduce but do not completely stop the chance of flooding as they can be overtopped, or fail.

Very low risk means that this area has a chance of flooding of less than 0.1% each year. This takes into account the effect of any flood defences in the area. These defences reduce but do not completely stop the chance of flooding as they can be overtopped, or fail.

Source: https://ckan.publishing.service.gov.uk/dataset/risk-of-flooding-from-rivers-and-sea1

Source: © Copyright Richard Humphrey and licensed for reuse under Creative Commons Licence.

Surface water flooding happens when rainwater does not drain away through the normal drainage systems or soak into the ground, but lies on or flows over the ground instead.

The flood depth is grouped into 6 bands measured in millimeters as shown in the map legend.

Source: https://ckan.publishing.service.gov.uk/dataset/risk-of-flooding-from-surface-water-depth-3-3-percent-annual-chance

Source: © Fernweh. / CC BY-SA 2.0

Flood Storage Areas shows those areas that act as a balancing reservoir, storage basin or balancing pond. Their purpose is to reduce the effect an incoming flood on the 'downstream' area of the river. It may also delay the timing of the peak of a flood peak so that its volume is discharged over a longer time interval. It should be noted that flood storage areas do not completely remove the chance of flooding and can be overtopped or fail in extreme weather conditions.

Source: https://ckan.publishing.service.gov.uk/dataset/flood-map-for-planning-rivers-and-sea-flood-storage-areas

Source: © Terry Jacombs / Cox's meadow flood storage basin. / CC BY-SA 2.0

An SMP is a non-statutory plan providing a large-scale assessment of the risks associated with coastal processes. It presents a policy framework to reduce risks to people and the developed, historic and natural environment. The 'SMP web link' layer places points on the map which you can click on to get more details and a link to the actual plans.

There are four types of approaches to managing the coastline as outlined below using the following symbols on the map

Hold the Line (HTL): an aspiration to build or maintain artificial defences so that the current position of the shoreline remains. This can involve maintaining or changing the standard of protection.

Advance the Line (ATL): by building new defences on the seaward side of the original defences. This is rarely used and is limited to policy units where there is significant land reclamation is considered. There are no policy units in Wales assigned ATL.

Managed Realignment (MR): by allowing the shoreline to move backwards or forwards naturally but managing the process to direct it in certain areas.

No Active Intervention (NAI): where there is no planned investment in coastal defences or operations, regardless of whether or not an artificial defence has existed previously. The coastal management approach for a certain section of coast may change from the status quo where a policy may no longer be practical or acceptable over 100 years. Therefore, a combination of policies may be proposed over the length of the SMP. The dataset identifies which of the second-generation Shoreline Management Plans are applicable to a particular stretch of the Welsh coastline and the policies assigned to policy units related to that particular area. This dataset is a polyline, spatial data layer for the Welsh coast only.

You can find a fuller explanation here

Source: © Christine Matthews / Cox's meadow flood storage basin. / CC BY-SA 2.0