The height of the dike ranges to 40 in.
These rise generally only a few feet above the level of the sea, and are crowned by a single house standing on an artificial mound and protected by a surrounding dike or embankment.
These are represented by the famous sea dikes called the Westkapelle dike and the Hondsbossche Zeewering, or sea-defence, which were begun respectively in the first and second halves of the 15th century.
In 1901 the government introduced a bill in the States General, based on the recommendations of the commission, providing for enclosing the Zuider Zee by building a dike from the North Holland coast, through the Amsteldiep to Wieringen and from that island to the Friesland coast at Piaam; and further providing for the draining of two portions of the enclosed area, namely the N.W.
In this way the towns of Rotterdam, Schiedam, Vlaardingen and Maasluis have all gradually extended over the Maas dike in order to keep in touch with the river, and the small town of Delftshaven is built altogether on the outer side of the same dike.