The influence of ice on sediment transport, deposition and reworking in a temperate mudflat area, the Danish Wadden Sea

The impact of ice formation on the transport, deposition and reworking of sediment at temperate intertidal mudflats has only been little studied. Investigations at the Kongsmark tidal flat in the Danish Wadden Sea reveal that sediment transported incorporated in drifting ice floes and deposited as melt out sediment may significantly influence both the sediment balance and the morphology of intertidal mudflats and supra tidal salt marshes. It was found that sediment deposited as melt out sediment from ice floes may account for a major part of the net accumulation on the fringing salt marshes, and it is suggested that sediment in the intertidal is transported from the lower part of the mudflat towards the higher lying parts thus influencing both the micro relief and the slope of the mudflat significantly. The transport distance was estimated to be at least in the order of 2 km, and the transport from the intertidal onto the salt marsh was found to be a one way transport process because vegetation quite rapidly grows through the melt out sediment, thus preventing resuspension. The results suggest that the ice transport process can be defined as a secondary process because it almost exclusively redistributes sediment already imported to the estuary. This is contrasting the primary estuarine processes of settling–scour-lag, tidal pumping and estuarine circulation which continuously concentrate cohesive sediment in the estuarine waters.