29 Brackish tidal marshes of the Scheldt

The geosite includes the Scheldt, including outer dike salt marshes, from Burcht to the Belgian-Dutch border. The salt marshes cover a very limited area in this geosite: they form a narrow strip (100 to 350 m wide) in the inner bends of the Scheldt. The outer dike salt marshes are at 5 to 6 m TAW. This is higher than the inner dike areas of the Wase Polders (1.5 to 4 m TAW) and lower than the raised industrial and urban zones (6.5 to 8.5 m TAW). The Scheldt is 350 m to over 1 km wide in this zone and is under tidal influence. The part of the estuary in question has a large gradient in salinity over short distances and strong fluctuations in salinity throughout the year. It is therefore the zone where tidal vegetations with reeds and willow occur alongside salt-loving plant species. The latter increase downstream.

51.363857789812, 4.2460558674438

Origin of the landscape

During part of the Pleistocene there was no Scheldt in this area, drainage was via the Flemish Valley. At the end of the last ice age, this valley was dammed up by the Maldegem-Stekene sand ridge and the Scheldt took its present course. So it is only since the beginning of the late glacial that the Scheldt passes Antwerp. A very last cold phase caused a barren landscape and formation of cover sand ridges. From the Early Holocene, forests developed again. These held precipitation better and prevented erosion, therefore the Scheldt turns into a small stream within a swampy forest. About 6,500 years ago, the tide reached the region for the first time since the last ice age. During this phase, peat development was interrupted by mudflats and salt marshes. About 500 years later, the tidal action disappeared again and the formation of the peat bog that had already covered the entire valley by 5,000 years ago resumed.

Mudflats and salt marshes

About 2,500 years ago, the barrier of coastal dunes in Zeeland broke through. This allowed the tide to enter the land more easily. Once again, peatlands gave way to mud flats and salt marshes. From the 13th century AD, the areas along the Scheldt were reclaimed and the mud and salt marsh landscape was limited to a narrow zone along the Scheldt, as it still is today.