- Coastal Flood Boundaries - additional help and further information
- Where can I access the Coastal Flood Boundaries data and guidance documents?
- How is sea level rise accounted for in the Coastal Flood Boundaries?
- I am concerned about the large differences in values in some locations and the effects on my project
- Levels have fallen in my area of interest since the previous Coastal Flood Boundaries update. How can this be when sea levels are known to be rising?
- What has changed in Coastal Flood Boundaries 2018?
- I’ve been given mean high water springs (MHWS) and highest astronomical tide (HAT) predicted Tide Levels by another source. They don’t match up to those in the Coastal Flood Boundaries. Which should I use?
- How are levels within ‘Inland Extensions’ or ‘Estuaries’ derived?
- How should I use Coastal Flood Boundaries levels in estuaries and tidal rivers?
- What are the key outputs of Coastal Flood Boundaries 2018?
- What has been done to update the Coastal Flood Boundaries in 2018?
- Why are regular updates, and therefore likely change in the estimates, necessary?
- How often is the Coastal Flood Boundaries dataset updated?
- How can I generate my Base Tide Curves?
- Are waves included in the Coastal Flood Boundaries?
- What information is included in the extreme sea levels shapefiles?
- What is the accuracy of the Coastal Flood Boundaries extreme sea levels?
- What is the vertical datum of the Coastal Flood Boundaries Level?
- What is the base year for Coastal Flood Boundaries levels?
- What is meant by Annual Exceedance Probability (AEP) and which extreme sea level probabilities are included?
- How does the Coastal Flood Boundaries inform us about flood risk around the UK coast?
- Who should use the Coastal Flood Boundaries (CFB) data?
- What are the Coastal Flood Boundaries?
What information is included in the extreme sea levels shapefiles?
Created: 03 October 2019 Updated: 03 October 2019
Both the CFB_Extreme_Sea_Levels_2018.shp and CFB_Extreme_Sea_Levels_Estuary_2018.shp shapefiles contain 16 extreme sea levels (prefixed ‘T’). They also include 16 lower (2.5%) and upper (97.5%) confidence levels (prefixed ‘C_T1’ and ‘C_T2’ respectively).
Each extreme sea level value represents the peak total sea level that occurs during a tidal cycle associated with particular extreme probability. Predicted tidal levels combine with storm surge to produce the extreme peak sea level. Information on how to generate a design time series tide curve using CFB extreme sea level and surge information is provided in the supporting documentation: Coastal flood boundary conditions for the UK: update 2018, User report.
The confidence levels provided account for statistical uncertainty in the skew surge joint probability method. They do not take account of uncertainty due to interpolation using model data or predicted tidal variation between gauge sites. Locations of gauge sites used in the statistical analysis are given in CFB_Gauge_Data_2018.shp.
The shapefiles also include information on base year and Highest Astronomical Tide (HAT) and Mean High Water Spring (MHWS) predicted tide levels (not suitable for navigation). The location and chainage of each point is given.
Location chainage information included in the shapefiles is unchanged from CFB 2011 where the same location has been included in CFB 2018.