3.2. Probability density functions
To examine both high- and low water levels and their occurrence in the Rhine–Meuse channel network in high detail, probability density functions of water level records have been calculated. To detect changes in water level distribution through time, four centroids labeled were determined corresponding to adjacent segments in a pdf, separated by the two peaks and one local minimum in a of a tidal signal (Fig. 5). When the tidal amplitude decreases, the two peaks of the approach each other, and so do When tidal amplitudes are negligible, is single-peaked, and only the two centroids are calculated. The two centroids in a single peaked are considered to correspond to the two centroids of the segments including the tails of the distributions in the double peaked. Using this method, the characteristics of a pdf can be