CONDITIONS IN HOLLAND AND BELGIUM A large part of Holland and some portions of Belgium are below the normal sea level and are protected from inundation by artificial embankments (dikes) or by narrow belts of sand dunes. The foreshore works on the coast of Holland and Belgium, although of great interest and attended with considerable success, do not afford examples to be followed as affecting the sea defences of Great Britain and other countries exhibiting physical char acteristics similar to those of the latter. The protection works in such cases as Blankenberghe, Heyst, Scheveningen, Kallantsoog and Petten are of great magnitude and the engineers responsible for these works, particularly in Holland, have at their command the accumulated experience of centuries of sea-defence work.
The local conditions with which these works have to conf orm viz., low flat foreshores consisting entirely of sand—are wholly different to those generally associated with sea-defence works in England. The large expenditure involved is justified by the neces- sity of securing the not only of the sea-board, but of large tracts of the countries selves. Investigations in Holland are said to indicate a continuous subsidence of the land of that country relative to the sea level, amounting to about 15cm. per century.
The North sea foreshores of Holland and Belgium consist for the most part of fine sand ; sim ilar deposits border the lower portions of the numerous river estuaries which penetrate far inland, but in the higher parts of these the foreshores are generally composed of fine sand covered with clay or mud. The foreshores of the North sea between high and low water have an average gradient of about i in 45 and the shores above high water normally slope at about i in 25. Submerged sandbanks more or less parallel to the shore are a characteristic feature of the North sea and estuary coast-lines of Holland and Belgium. These, where they exist, afford considerable protection to the sandy shores during on-shore gales. In calm weather and with off-shore winds sand accumulates on the foreshores.