Delta Works was completed by the Europoortkering which required the construction of the Maeslantkering in the Nieuwe Waterweg between Maassluis and Hoek van Holland and the Hartelkering in the Hartel Canal near Spijkenisse. The works were declared finished after almost forty years in 1997. In reality the works were finished on 24 August 2010 with the official opening of the last strengthened and raised retaining wall near the city of Harlingen, Netherlands. Due to climate change and relative sea-level rise, the dikes will eventually have to be made higher and wider. This is a long term uphill battle against the sea. The
Geography of the European Netherlands (Nieuwerkerk aan den IJssel) , "below" sea level. "highest point on European mainland:" Vaalserberg above sea level. "highest point (including the Caribbean islands):" Mount Scenery on Saba above sea level. Natural resources: natural gas, petroleum, peat, limestone, salt, sand and gravel, arable land Land use: (2011) "arable land:" 25.08% "permanent crops:" 0.88% "other:" 74.04% Irrigated land (2007): Total renewable water resources (2011): Natural hazards: flooding by sea and rivers is a constant danger. The extensive system of dikes, dams, and sand dunes protect nearly one-half of the total area from being flooded during the heavy autumn storms from the north-west.