16. Why does some of the analysis show the cliffs “growing towards France”?
The error within the historic mapping, or aerial photography used as the basis for the BMP can be greater than the rate of erosion at that time. This is normal when using historic data sets, with error both within the survey undertaken at that time or when referencing older data to more recent mapping.
The resulting erosion rates could appear on the face of it to show the cliffs advancing as opposed to retreating (or not moving) as would be expected.
The transect method for measuring erosion has been used by CH2M partly to avoid areas of the largest error with the historic datasets.