The Great Stour Project - River and Coastal Flooding

GEOLOGY

The geology of the Stour catchment comprises sedimentary rocks of Cretaceous age or younger.

The oldest rocks are located in the south-west where erosion of the Wealden anticline has revealed Weald Clay, Lower Greensand and Gault Clay. These rocks were originally deposited as horizontal layers on the floor of an ancient sea and subsequently buried beneath an enormous accumulation of chalk, over 2000 metres thick in places.

During the Tertiary period forces associated with the formation of the Alps in southern Europe produced a series gentle flexures in the Cretaceous sediments, forming the Wealden anticline and Thames Basin.

Superimposed upon the larger structures are smaller scale folds such as the Wantsum syncline and the Thanet pericline in north-east Kent.

Weathering and erosion have since removed the top of the anticline exposing the softer rocks lying below the chalk. Since the various strata differ in resistance to erosion they have been removed at different rates.

In East Kent, the most resistant rock is the Chalk which forms an escarpment running from north-west to south-east. It is the eastern extremity of the North Downs, which mark the northern rim of the Wealden dome and extend for over 100 kilometres through Surrey and Kent to terminate abruptly at the White Cliffs of Dover.

From Dover to Ashford, the steep south to south-westerly facing scarp is a striking feature of the landscape, with a crest height of around 180 metres above sea level. From Castle Hill (TR214379), near Folkestone, there is a good view of the scarp face of the North Downs running toward the north-west, rising above the clay lowland and the Eurotunnel terminal near Folkestone.

Further west, there is a another fine view of the southerly facing chalk scarp over Folkestone Warren.

To the north-east, the chalk dips gently toward the Thames Estuary. In north-east Kent, it is buried under a cover of recent sediments in the Wantsum Channel, to reappear in the Isle of Thanet before it’s final descent in the Thames Estuary. From the cliffs at Kingsdown (TR380467) there is a marvellous view to the north, down the dip of the Chalk, toward Deal with the Isle of Thanet beyond.