The southwestern marine clay area covers a large part of Zeeland and the South Holland islands. It is divided chronologically into oldland and newland. The new land includes the eastern part of Schouwen-Duiveland, the northern part of Tholen, St. Philipsland, a small part of Walcheren, Noord-Beveland, the western and eastern part of Zuid-Beveland, and most of Zeeuwsch-Vlaanderen . From the middle of the 13th century, dikes were no longer built so much to defend existing land, but also to reclaim 'new' land. The areas belonging to this are called new land and consist of both rising and accretion, as well as silted up 'drowned' old land (such as Noord-Beveland). Wax ups are flats or salt marshes that form in the middle of the water under the influence of the tides. Accretion is accretion against land that has already been embanked. In Nieuwland polders there are often remnants of creeks, which were closed off from the outside water by the dykes. The Nieuwlandpolders are more silted up and less settled than the Oudlandpolders and are therefore relatively high in the landscape. The soil structure is much more uniform than that of the oldland polders. The habitation in the Nieuwlandpolders was not tied to certain high-lying areas; the polders were flat and had good natural drainage. As a result, a large part of the land could also be used for arable farming (including grain, madder and flax, later potatoes and sugar beets) and fruit growing. Only the lowest parts along the creeks were used as grassland. The layout of the polder is usually rational: a rectangular, relatively large-scale allotment with straight roads. The farms were built scattered in the polders, the newly founded settlements were concentrated along the roads and dikes (road and dike villages). Front street villages were built from the 15th century. Various polders have been flooded several times. Major floods have been the storm surges of 1134, 1248, 1375, 1421 (Second Elisabeth Flood), 1530/32 (North Beveland and South Beveland), 1570 (Land van Saeftinghe) and 1953. In the current landscape, weels and creeks indicate where the dikes have broken. In response to the floods, embankments were constructed. The inlaagdijk was laid in places where the existing dike threatened to break through. The area between this dike and the old seawall is called an inlayer. Inlays mainly occur where a deep channel ran close to the dike and where the subsoil was weak (young sea sand). To strengthen dykes, clay was often excavated from the inlays, creating elongated pools, separated from each other by dams. Because this clay was transported with carts, these areas are called cart fields. In the 19th century, the landscape of the Nieuwlandpolders was strongly influenced locally by the construction of railways, canals and dams, followed later by the inundation of 1953 and large-scale reparcelling.
