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 s ediment at temperate intertidal mudflats has only been little studied. Inve stigations at the Kongsmark tidal flat in the Danish Wadden Sea reveal that sediment transported incorporated in drifting ice Bees and deposited as me lt out sediment may significantly influence both the sediment balance and t he morphology of intertidal mudflats and supra tidal salt marshes. It was f ound that sediment deposited as melt out sediment from ice flees may accoun t for a major part of the net accumulation on the fringing salt marshes, an d it is suggested that sediment in the intertidal is transported from the l ower part of the mudflat towards the higher lying parts thus influencing bo th the micro relief and the slope of the mudflat significantly. The transpo rt distance was estimated to be at least in the order of 2 km, and the tran sport from the intertidal onto the salt marsh was found to be a one way tra nsport process because vegetation quite rapidly grows through the melt out sediment, thus preventing resuspension. The results suggest that the ice tr ansport process can be defined as a secondary process because it almost exc lusively redistributes sediment already imported to the estuary. This is co ntrasting the primary estuarine processes of settling-scour-lag, tidal pump ing and estuarine circulation which continuously concentrate cohesive sedim ent in the estuarine waters. (C) 2000 Elsevier Science Ltd. All rights rese rved.