page_title: Coastal management
section_title: Groynes
hierarchical_section_title: Coastal management / Construction techniques / Hard engineering methods / Groynes
caption_attribution_description: Groyne at Mundesley, Nofolk
context_page_description: Coastal management is defence against flooding and erosion, and techniques that stop erosion to claim lands.
  Coastal zones occupy less than 15% of the Earth's land area, while they host more than 45% of the world population. Nearly 1.4 billion people live within 100 km of a 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.
  Protection against rising sea levels in the 21st century is crucial, as sea level rise accelerates. 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.
context_section_description: Groynes are ert or walls perpendicular to the coastline to trap the sedimentation of longshore drift to gradually create a beach and for it ongoing protection by eliminating coastal erosion, often made of greenharts, concrete, rock or wood. Material builds up on the downdrift side, where littoral drift is predominantly in one direction, creating a wider and a more plentiful beach, thereby protecting the coast because the sand material filters and absorbs wave energy. However, there is a corresponding loss of beach material on the updrift side, requiring another groyne there. Groynes do not protect the beach against storm-driven waves and if placed too close together create currents that carry material offshore. Shapes of groynes can be straight, outwardly curved away in opposite direction from downdrift.
  Groynes are cost-effective, require little maintenance and are one of the most common defences. However, groynes are increasingly viewed as detrimental to the aesthetics of the coastline and face opposition in many coastal communities.
  Groynes can be considered a "soft" solution because of the beach enhancement.
  Groyne construction creates a problem known as terminal groyne syndrome. The terminal groyne prevents longshore drift from bringing material to other nearby places. This is a problem along the Hampshire and Sussex coastline in the UK; e.g., at Worthing.
caption: Groyne at Mundesley, Norfolk, UK
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