Sediment distribution and transport in the shallow coastal waters along the west coast of Denmark

Abstract

Until recently, studies of the regional distribution of seabed sediments off the littoral zone of the Danish North Sea coast had been concentrated on the Jutland Bank area (Fig. 1; Leth 1996, 1998). Knowledge on the sedimentary conditions and processes along the entire west coast of Jutland has, however, significantly increased as a result of 2000 km of newly acquired high-resolution seismic and side-scan sonar data, supplemented by about 100 vibrocores. These data were collected by the Geological Survey of Denmark and Greenland (GEUS) during joint projects with the Danish Coastal Authority between 1998 and 2001 (Leth et al. 1999; Larsen & Leth 2001). The coastal zone off west Jutland displays a highly dynamic environment, where sediment transport is governed by strong tidal and wave-induced currents. The net wavegenerated current is south going, while the coastal current has a net direction towards the north (Knudsen et al. 2002). The direction of the net littoral drift is southward from the outlet of Limfjorden to Blåvands Huk, with net erosion north of Nymindegab and aggregation to the south; the offshore part of this depositional system has recently been studied (Larsen & Leth 2001).

Formation mechanisms for self‐organized kilometer‐scale shoreline sand waves

“…Thus, it seems that offshore features should be excluded as the primary cause of shoreline sand waves. This is also confirmed by the observed sea bed geology off the Danish west coast [ Leth et al , ]. Similarly, the hypothesis that they were related to surf zone bars seems unlikely since Kaergaard et al [] found little correlation between the shoreline undulations and the breaker bars.…”

“…While the morphodynamic instability hypothesis is very plausible, another possibility is that sand waves were forced by offshore bathymetric features. Off the Holmslands Tange coast there is a thin layer of mobile sand [ Leth et al , ], and tidal and current sand waves have been documented [ Anthony and Leth , ]. However, their wavelengths are an order of magnitude smaller than those of shoreline sand waves.…”

Late Quaternary stratigraphy and morphogenesis in the Danish eastern North Sea and its relation to onshore geology

“…1 million m 3 is transported away to Fan0 and the Wadden Sea area (Kystdirektoratet, 2001). The coast south of Ringk0bing Fjord is presently aggrading about 0.5 -2 m/year, this is in contrast to the long stretch of coast north of the study area where net erosion takes place (Kystinspektoratet, 1998;Leth et al, 2004). The cape of Blavands Huk is separating the southern end of the wave-dominated, microtidal, simplified west coast of Jutland and the northern limit of the mesotidal Wadden Sea (Fig.…”

“…It is generally assumed that the Weichselian proglacial river plains extended westward off the west coast of Jutland forming the featureless seafloor in this part of the North Sea (Houmark- Nielsen & Kjaer, 2003). However, very little has been published on observations of the Quaternary sequence below the seafloor within 50 km off the west coast of Denmark (Liineburg, 1967;Foged, 1987;Leth et al, 2004). A rim of Holocene marine forelands such as spits and barriers has developed between the glacial landscape and the present day coast (Fig.…”

“…In the Wadden Sea area, this rim is a prism of mainly submarine tidal deposits (Bartholdy & Pejrup, 1994) protected by a row of barrier islands from R0m0 in the south, to Fan0 and the peninsular Skallingen in the north (Aagaard et al, 1995;Bartholdy & Pejrup, 1994). Recent studies indicated that the seabed off these areas was acting as a depocenter in the Holocene (Leth et al, 2004).…”