Défense côtière (écologie)

Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands. Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates due to climate change. Changes in sea level damage beaches and coastal systems are expected to rise at an increasing rate, causing coastal sediments to be disturbed by tidal energy. Coastal zones occupy less than 15% of the Earth's land area, while they host more than 40% of the world population. Nearly 1.2 billion people live within 100 km of shoreline and 100 m of sea level, with an average density 3 times higher than the global average for population. With three-quarters of the world population expected to reside in the coastal zone by 2025, human activities originating from this small land area will impose heavy pressure on coasts. Coastal zones contain rich resources to produce goods and services and are home to most commercial and industrial activities. Coastal engineering of harbours began with the origin of maritime traffic, perhaps before 3500 B.C. Docks, breakwaters and other harbour works were built by hand, often in a grand scale. Ancient harbour works are still visible. Most of the grander ancient harbor works disappeared following the fall of the Western Roman Empire. Most coastal efforts were directed to port structures. Venice and its lagoon is an example of measures not related to ports. Protection of the shore in Italy, England and the Netherlands began in the 6th century or earlier. The ancients understood phenomena such as Mediterranean currents and wind patterns and the wind-wave cause-effect link. The Romans introduced many innovations in harbor design. They built walls underwater and constructed solid breakwaters. These structures were made using Roman concrete. In some cases wave reflection was used to prevent silting. They used surface-height breakwaters to trip the waves before they reached the main breakwater. They were the first dredgers in the Netherlands to maintain the harbour at Velsen.