Abstract:

The migration of submarine, coastal and desert dunes is influenced by their morphological parameters. Analysis of the wave height and length of some representative largescaled dunes indicates that these parameters are highly different among the submarine, coastal and desert dunes, with the height being the smallest for the submarine dunes and the largest for the desert dunes for the same range of lengths. Such phenomena are mainly due to the difference in the thickness of the fluid over the bedforms and secondly due to the sediment supply. In shallow marine environments, the water depth represents a limiting factor for upward growth of the dunes, whilst on land the thick atmospheric layer provides the space for dune growth; in deserts, relatively abundant sand supply, as compared with the coastal environment, results in full growth of the dunes. There tends to be deviations of the heightlength data points from statistical HL curves; numerical experiments demonstrate that such deviations may be associated with the bedload transport rate. Along the transport pathways, if the transport rate increases or decreases, then the resultant HL data may systematically deviate from the standard curve; likewise, rapid decrease in the transport rate can reduce significantly the dune migration rate, which causes upward accretion of sand and may form extremely high dunes. This behavior  can be used to control the rate of dune migration, on the basis of a distanceduration curve and appropriate design of dune height. An example of deriving the distanceduration curve is provided in the present study. The designed height may be realized by artificial measures such as a fencing system, low walls and trenches in front of the dunes, and the deployment of armoring layers on the bed.

Key words: bedform parameters; HL relationship; bedload transport; dune migration; distanceduration curves, dune height design; Taiwan Strait; southwestern French coast