Jetty


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coast protection

coast protection, methods used to protect coastal lands from erosion. Beaches can exist only where a delicate dynamic equilibrium exists between the amount of sand supplied to the beach and the inevitable losses caused by wave erosion. Various activities of man have upset this equilibrium, decidedly increasing the rate of erosion of the shorelines. For example, the plethora of dams constructed across major drainage systems has served to entrap sediment that would normally reach the coastal zone, imperiling the existence of beaches by cutting off their natural sand supply. Mining of beach sand has removed millions of tons of sand from coasts and drastically upset the balance between natural supply and losses. Historically, people have considered coast protection a local problem and have attacked the problem by building structures to inhibit the transportation of sand from a local area. However, it has been learned that building structures to solve a local erosion problem may extend and intensify the erosion problem along nearby beaches, requiring the construction of structures along an entire coast. For example, many structures block littoral drift, which is a movement of sand parallel to the coast, both on the beach and offshore, caused by waves. The blockage results in a depletion of sand downcurrent from the structure. Several different kinds of structures are built. Sea walls are constructed at the edge of the shore facing the ocean waves. Designed to protect only the beach areas behind them, they cause an increased loss of sediment in front of and beneath them. Breakwaters are long piers built offshore parallel to the shoreline; they are designed to provide calm anchorages in an area behind them called a wave shadow. At the breakwater off Santa Monica, Calif., the wave shadow impeded the littoral drift, producing a deposition of sand behind the breakwater and extensive erosion of the beach downcurrent. Groins are lines of rock or pilings constructed perpendicular to the shoreline. They act as a partial barrier to littoral drift, trapping sand on the updrift side and causing erosion on the downdrift side. Jetties are often built at river mouths and harbor entrances, projecting out into the ocean to direct and confine littoral currents and to prevent silting of the harbor entrance. Jetties cause the same problems of downdrift erosion as groins. In some instances it has been necessary to pump the sand trapped by the structure to adjacent beaches downdrift. Efforts have also been made to prevent erosion using the natural materials at hand. Artificial dunes have been built by bulldozing sand back from the beach or by placing snow fences to trap windblown sand. Since beaches themselves are effective in dissipating wave energy, one remedy to the lack of a sand supply is to pump sand directly onto the beach from interior or offshore zones. Unlike other human-made structures, artificial beaches do not harm the shore downdrift.
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Jetty

The upper story that juts out over the lower story of a timber-framed house.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Jetty

 

a hydraulic-engineering structure used to regulate the flow of a watercourse and to protect a seashore or riverbank from erosion. Earth, stone, concrete, fascines, and gabions are used as building materials for jetties. Jetties are built perpendicular or at an angle to the shore. Bottom jetties protect the foundations of shore structures (levees or retaining walls) from erosion.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

jetty

[′jed·ē]
(anatomy)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

jetty

A projecting part of a building, as a bay window or the upper story of a timber house.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
The structures, which measure 17.6 metres by 18.7 metres, slot into the jetty and move up and down with the tide to prevent the ship's overhanging flight deck from colliding with the jetty.
"When I asked the officials on how the fishermen would reach the sea with no jetty, they said using the shore to sail is prohibited since it is an unofficial jetty, but being in the sea was not," Mr Al Sinan told the GDN from the site.
Kiva Sales and Services (KSS) has announced a distribution partnership with Jetty Extracts, one of the largest vape brands in California.
Fly anglers enjoyed a rod average of eight, with most coming from the jetty and overflow end of the dam.
A MERCHANT shipping company says it has restarted using a jetty but will only continue to do so if new safety standards are maintained.
M2 EQUITYBITES-August 14, 2019-Kiva Sales and Service Acquires Jetty Extracts for Distribution and Sales
A press statement issued by the Chief Minister's office said greenfield ports and multi-purpose jetty developers will have to make 100 percent capital investment and handle 50 percent cargo in the first 35 years.
START your 3.6 mile walk around Brandelhow Park, Cumbria, at Hawes End Jetty.
The first of 42 trestles that will make up the 1.2km long jetty at Vassiliko was installed last week to enhance the under-construction oil storage terminal of VTTV.
1 Standing on Hawes End Jetty, turn to your left and head south for half a mile along the wide track which runs parallel to the lake shore.
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There were anxious moments for the passengers of an express boat on the Rejang river, near here today when the boat sprung a leak after hitting a jetty steel barrier.