seaward of the dune foot and above the level (glw-h) The position of the momentary coastline (SKL) is defined in relation to the national beach pile line as: (A/2h) - Xdv The background of this method is that the thickness of the sand layer to be taken must be a function of the measuring wave height; however, it is unknown. But because the elevation of the dune foot is also a function of the measuring wave height, the value h is a good representation of the effect of both tide and wave influences. For the determination of the beach profiles, the so-called JarKus profiles are measured along the coastline. These profiles are roughly 250 metres apart and are measured annually from around 800 meters in the sea to just behind the dunes. These measurements are available throughout the coast from 1965 onwards. From the period from about 1850 there are also profile soundings available in some places, but these are often slightly shifted compared to the jarkus rowing and are therefore more difficult to analyse. In the case of groynes, the sounding is carried out exactly in the middle between the groynes. The Basic Coastline (BKL) The Basic Coastline is by definition the coastline of 1 January 1990. But of course there are no measurements made on exactly that date, moreover, there are always variations in the measurements. The BKL is therefore determined by taking the beach measurements of the approximately 10 years prior to 1990 and by determining the MKL for each of those years. These values are placed in a graph, a regression line is determined. Where this regression line cuts the date 1-1-1990 lies the basic coastline BKL. In principle, the location of the BKL is immutable. In very special cases, where the coast is substantially altered by a work, it can be decided to shift the BKL. This is not based on a technical or morphological calculation, but actually a political decision. An example of this is the Hondsbossche Zeewering, as sea dike near the village of Petten, where the BKL was actually on the toe of the dike. Due to the construction of a new artificial dune in front of this dike (the Hondsbossche Duinen), a piece of dune was added, of which the intention is to preserve it. So there is the BKL shifted seaward. The coastline to be tested (TKL) Within the framework