North of the Hinder Banks sand waves are found (height 3–15 m) the steep side of which points to the south. Further to the north the steep side of the sand waves is directed northward. There is no explanation as yet for this phenomenon. In fact regarding displacements of sand waves little is known. In one location it was observed that the height of the sand wave crests depends on the frequency of occurrence of heavy gales which erode the crests and the length of the intermediate calm weather period in which the crests are building up. The maximum observed variation in the height of the sand wave crests was about 2 m.Wandering mega-current ripples (height 0.2–2 m) were observed on the flanks of the sand waves. The crests of these current ripples often make an angle with the sand wave crests. In many locations it was observed that the travelling direction of these ripples, according to their asymmetry is directed towards the crest of the sand wave from both sides.The grain size differs significantly from one place to another. |
