the design of supplements to prevent erosion. Use of measurements for nourishment design To compensate for coastal erosion, the design of a supplementation is actually very simple, every year the same amount of sand has to be applied as erosion disappears annually. The assumption is that there is no significant change in the wave climate and the orientation of the coastline. With most nourishments, this is a correct assumption. In case of substantial changes in the coastal orientation, this method is therefore not always usable (e.g. in the design of the sand engine). In practice, the length of the nourishment must be 20-40 times the width in order to apply this method. In short, the method consists of the following steps: Make sure there are enough measured profiles (at least 10 years). Use these profiles to calculate the annual sand loss (in m3/year) for a coastal section. Multiply this amount by an appropriate lifetime (e.g. 5 years). Add a loss factor (order 40 %). Place this amount of sand somewhere on the beach between the low water line and the dune foot. To determine the amount of sand in the profile, the same method can be used as used for the basic Coastline. Given the fact that the instantaneous coastline has been measured for the necessary years and thus the decline of this coastline, determining the loss of sand is quite simple. Suppose the decline of the MKL is 5 m/year, then the annual sand loss is 5*(2h) m3 per year per linear meter of coastline. Here is 2h the height of the active beach profile. Along the Dutch coast, h is near Hoek van Holland in the order of 4 m, so in the above example the erosion would be 40 m3 per year per linear meter of coast. For a nourishment with a length of 4 km and a lifespan of 5 years is therefore 40*4000*5 = 80 000 m3. Because there is extra sand loss immediately after construction, a good amount is 1.4 *80000 = 112 000 m3. This is a seaward shift of 1.4*5*5= 35 m. In the practice of beach nourishments (from 1990 onwards), this method appears to work very well. Analyses of nourishments in northern Germany also show that this is a reliable method. The starting point is that the grain size of the nourishment sand is equal to the original beach sand. If