The first defenses against the sea went up some 800 years ago. Today more than 2,400 kilometers of dikes shield the low, flat land—almost half of which lies below sea level—from invasion by the North Sea.
Water management is an important issue for the Netherlands, as due to its low height, approximately two thirds of its area is vulnerable to flooding, while the country is densely populated.
Natural dunes and man-made dikes, dams, and floodgates provide defence against storm surges from the sea. River dikes prevent flooding from water flowing into the country by the major rivers Rhine and Meuse, while a complicated system of drainage ditches, canals, and pumping stations / windmills keep the low-lying parts dry for habitation and agriculture.
Dutch Water Authorities (water control boards) are the independent local government bodies responsible for maintaining this system.
