Geography Please Help!!!?

[rue]

we are learning things in geography on longshore drifts. well my question is "What are Groynes and how are they effective towards coastal defence. by the way im in year 8 or (Eighth grade) im in the United Kingdom

[JokerWannabe]

We havn't done this yet! It's out next topic! From what I can remember from Primary school is that Longshore drift is where sand from one part of a beach ends up on another part of a beach...I may be totally wrong but I have Geography tommorow. If we are doing about long shore drift tommorow, I will Re answer (edit) and tell you what I mean!

[joniboni]

A groyne (groin in the United States) is a rigid hydraulic structure built out from the shore (in coastal engineering) or from the bank (in rivers) and interrupts the flow of water and sediment. Groynes serve a multitude of functions.The best form of natural defence is a beach which efficiently absorbs the energy of the waves. Along many coasts, however, longshore drift causes the beach to thin out in places and erosion of the land behind becomes a problem. Groynes are designed to slow down longshore drift and build up the beach. They are usually made of tropical hardwoods which are more resistant to marine borers and erosion. A few are made of concrete, steel or in more recent times large rocks. They are built at right angles to the shore and spaced about 50-100 metres apart. Groynes may have a life of 15-20 years but often have to be replaced rather than repaired.Groynes are one of the most common and effective methods of coastal defense against transportation of sediment. Groynes are structures which run perpendicular to the shoreline. Groynes extend from the upper foreshore or beach down towards the sea, usually at right angles to the sea. Groynes are usually made of wood, concrete, or piles of large rocks. Groynes are generally constructed in groups called groyne fields.Groynes are wooden, concrete and/or rock barriers or walls perpendicular to the sea. Beach material builds up on the updrift side, where littoral drift is predominantly in one direction, creating a wider and a more plentiful beach, therefore enhancing the protection for the coast because the sand material filters and absorbs the wave energy. However, there is a corresponding loss of beach material on the downdrift side, requiring that another groyne to be built there. Moreover, groynes do not protect the beach against storm-driven waves and if placed too close together will create currents, which will carry sand material offshore.Groynes are extremely cost-effective coastal defense measures, requiring little maintenance, and are one of the most common coastal defense structures. However, groynes are increasingly viewed as detrimental to the aesthetics of the coastline, and face strong opposition in many coastal communities.Many experts consider groynes to be a "soft" solution to coastal erosion because of the enhancement of the existing beach.Cost – est. at £200,000 per groyne, £60 per metre[citation needed]In addition to being costly, there is also a problem called Terminal Groyne Syndrome. The last groyne that has been built or the terminal groyne, prevents longshore drift from bringing material to other nearby places. This is a common problem along the Hampshire and Sussex coastline in the UK.