Flood control is an important issue for the Netherlands, as due to its low elevation, approximately two thirds of its area is vulnerable to flooding, while the country is densely populated. Natural sand dunes and constructed dikes, dams, and floodgates provide defense 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 (historically: windmills) keep the low-lying parts dry for habitation and agriculture. Water control boards are the independent local government bodies responsible for maintaining this system. In modern times, flood disasters coupled with technological developments have led to large construction works to reduce the influence of the sea and prevent future floods. These have proved essential over the course of Dutch history, both geographically and militarily, and has greatly impacted the lives of many living in the cities affected, stimulating their economies through constant infrastructural improvement. History The Greek geographer Pytheas noted of the Low Countries, as he passed them on his way to Heligoland around BCE, that "more people died in the struggle against water than in the struggle against men". Roman author Pliny, of the 1st century, wrote something similar in his Natural History: There, twice in every twenty-four hours, the ocean's vast tide sweeps in a flood over a large stretch of land and hides Nature's everlasting controversy about whether this region belongs to the land or to the sea. There these wretched peoples occupy high ground, or manmade platforms constructed above the level of the highest tide they experience; they live in huts built on the site so chosen and are like sailors in ships when the waters cover the surrounding land, but when the tide has receded they are like shipwrecked victims. Around their huts they catch fish as they try to escape with the ebbing tide. It does not fall to their lot to keep herds and live on milk, like neighboring tribes, nor even to fight with wild animals, since all undergrowth has been pushed far back. The flood-threatened area of the Netherlands is essentially an alluvial plain, built up from sediment left by thousands of years of flooding by rivers and the sea. About 2,000 years ago most of the Netherlands was covered by extensive peat swamps. The coast consisted of a row of coastal dunes and