A document which describes the methodology in further detail will be available on outputs page when finallised. However, in short the methodolgy of the National Coastal Change Assessment is as follows:
- The OS 6 inch County Series maps from approximately the 1890's (which you can see here), along with OS maps from approximately the 1970's are georeferenced and used within ArcGIS along with a graphics tablet to hand digitise the coastline (the High Water Mark of Ordinary Spring line in the 1890's and the Mean High Water Springs line in the 1970's, which technically represent the same line, however there has been a change in terminology over time).
- The current Mean High Water Springs (MHWS) is derived from the OS MasterMap product, but where a digital terrain model (DTM) is available (either LiDAR or aerial photography based) the project team will extract the MHWS position using the known elevation of MHWS to extract a contour from the DTM.
Coastal Change and Implications
- The three coastlines are then analysed using a grid based system to determine the change (either erosion or accretion) over time, from which change rates can be established. These rates are then used to linearly extrapolate change into the future, along with the Coastal Erosion Susceptibility Model (CESM), to estimate the future position of the coast. Asset data is then used to determine the assets that will potentially be impacted by this change.
The NCCA has and will produce a number of reports, in addition to a range of GIS datasets. When the various project outputs have been produced they will be available for download here.