Understanding the data

The Environment Agency’s National Coastal Erosion Risk Map (NCERM) was released in 2011, following a project that began in 2006, with the aim to provide a map of erosion risk across all coastlines in England and Wales. The erosion risks can be plotted for the short (0-20 years, up to 2025), medium (20-50 years, up to 2055), and long term (50-100 years, up to 2105) and under three different confidence bands: 5th, 50th, and 95th percentiles. The 50th percentile is the mean erosion extent likely to occur over the specified time period, and the 5th and 95th percentiles are the maximum and minimum extent the erosion zone might reach, respectively, over the specified time period. All erosion distances are cumulative over time, and the erosion risks can be plotted either assuming the Shoreline Management Plans will be delivered or assuming no active intervention. 

In our analysis, we plotted the erosion risk for the long term (up to 2105) under the 5th percentile (as conducted in the Committee on Climate Change’s coastal report) to account for the full range of uncertainty. We also assumed all Shoreline Management Plans will be delivered by the end of the century for each of the analysed coastlines. 

The method to plot the coastal erosion extents on ArcGIS Online is detailed here.

The NCERM data and associated information is intended for guidance – it cannot provide details for individual properties. The NCERM information considers the predominant risk at the coast, although flooding and erosion processes are often linked and data on erosion of foreshore features are, in general, not included.  

The data describes the upper and lower estimates of erosion risk at a particular location, within which the actual location of the coastline is expected to lie. The dataset does not estimate the absolute location of the future coastline. Details of geologically complex areas, known as “complex cliffs” are, in general, not included within the dataset due to the inherent uncertainties associated with predicting the timing and extent of erosion at these locations. 

This dataset succeeds National Coastal Erosion Risk Mapping (NCERM) – National (2012 – 2017)  

Attribution statement: © Environment Agency copyright and/or database right 

National Coastal Erosion Risk Mapping dataset is usable under the Environment Agency Conditional Licence

NCERM combines cliff and slope erosion with the probability of defence failure. The EA developed a probabilistic method to calculate erosion predictions based on historic coastal retreat rates from monitoring programmes and risk-based inspections (RACE project). NCERM does incorporate some future sea level rise (SLR) but does not account for the most recent (UKCP18) SLR projections, nor the acceleration of this rate in the next 100 years. As a result, NCERM data could be underestimating erosion extents in the medium and long term, as rates of SLR are expected to increase over the next decades (Kirby et al., 2021). 

The Environment Agency is however updating NCERM to include the latest climate change projections, which is due to be released in 2023 (NCERM2).

NCERM only provides data for coastal frontages where the risk is from coastal erosion; it does not provide predictions where coastal flooding is the main risk. See our article for a summary of the risks from both coastal flooding and erosion.

Each country has their own coastal erosion dataset: NCERM for England, NCERM for Wales, and Scotland’s Dynamic Coast. Our map only includes the NCERM dataset for England. Moreover, to identify the coastlines at risk, we used the property impact dataset from the Committee on Climate Change which only assessed erosion impacts in England.

No. Our map is only showing the coastlines with the highest number of properties at risk based on currently available data. If your coastline is not featured in the map it does not mean it is safe from coastal erosion. There are many other areas that are experiencing erosion across the country, such as coastlines that have plans to maintain defences but not necessarily the funding or technical feasibility to support that. To find out estimated erosion predictions for your coastlines, click on the colour-coded SMPs on the map and view the information box on the left. This will tell you about the SMPs for the short, medium, and long term, as well as the future erosion predictions under a no-active-intervention scenario and a scenario in which the SMP is funded and implemented.

Policies in the SMPs were those agreed through public consultation processes so these are the ones that were used on the One Home map after consultation with the Environment Agency. During the SMP refresh process, some policies will inevitably change to reflect better the environmental and economic realities of the area. SMP policy discrepancies may exist on the map in areas where policies haven’t yet been decided. The NCERM can only select one policy to model erosion predictions and this policy may therefore differ to those outlined in the Shoreline Management Plans.

This dataset from the Committee on Climate Change (CCC) provides estimates on the number of residential properties at risk from erosion by 2105 for most coastlines in England under a scenario in which all Shoreline Management Plans are implemented. The dataset was accessed following a freedom of information (FOI) request submitted in May 2021 by an unknown organisation.  The dataset is an intermediary to the summary provided in their “Managing the Coast in a Changing Climate” 2018 report.

The method to calculate the number of at-risk properties for each coastline is outlined in the method statement to the CCC’s coastal report entitled “GIS-based assessment of coastal flood and erosion risk in England” (Sayers 2018). In brief, the erosion risk zones (NCERM) were mapped against property data to determine the number of properties overlapping at-risk areas.

The dataset is an intermediate stage to the summary provided in the “Managing the Coast in a Changing Climate” report; therefore, it should be viewed as such and not directly used to support policy decisions. The results should not be relied upon on the localised scale and further developments could improve some of the assumptions made. However, the insights remain insightful and useful at the scale of England and for national policy considerations.

Satellite mapping images confirm that a significant number of at-risk properties identified by the CCC on the Holderness Coast are static caravans. To distinguish between the number of properties at risk and the number of caravans at risk – and in the absence of a property dataset – we used a proximity analysis tool on ArcGIS mapping software to count the number of buildings (OS Local Buildings Layer) overlying the erosion zone. As the OS buildings layer does not include static caravans, we assumed that the number of buildings overlying the erosion zone represents the maximum possible number of properties at risk of erosion (as some buildings will not be domestic properties). We then subtracted this number from the total number of properties at risk (quoted by the CCC) to estimate the minimum number of caravans at risk. As this analysis relies on existing analysis, the conclusions should be caveated in that context.

Property damage estimates for most coastlines were calculated by multiplying the number of at-risk properties by the average house prices over the last year from Rightmove’s website (accessed from the Land Registry’s property datasets).

Average house prices were unavailable in coastlines where no properties have been sold in the last year or where erosion risks only affect isolated houses over long coastlines (making it difficult to obtain an average house price for the region). For these coastlines, we either used the Land Registry’s average house price for local authorities (house price index for Oct 2022) for property damage calculations or performed location-specific analyses using property price information (Rightmove) from previous years (see the method below for the Holderness coast). The caveats and sources for each location are indicated on the map.

To calculate damage estimates for the Holderness Coast, we manually identified the streets overlying the 2100 erosion zone using ArcGIS’s satellite basemap. We then used Rightmove’s map to get sales data on properties sold in these locations. This data was used to calculate the average house price for the coastal unit, which was then multiplied by the number of properties at risk, excluding static caravans (see Section 2 on estimating the number of properties and caravans at risk in the Holderness Coast).