Fixed breakwaters are semi-permanent structures that require construction by a knowledgeable person with an understanding of the area's wave transmission. Construction costs can be relatively high when compared to floating breakwaters. Breakwaters that are continuous can pose an ecological hazard when placed in wetlands by barring organisms from entering or leaving. Fixed breakwaters are often an eyesore--an aesthetically displeasing sight on the shoreline.
Credits:http://www.ehow.com/list_6830350_pros-cons-breakwaters.html
Tuesday 26 June 2012
Effectiveness of breakwaters
Fixed breakwaters usually consist of mounded rubble or concrete barriers. These types of breakwaters offer protection from high and fast-moving waves and can still offer protection even if mildly damaged in heavy storms. Stone or rubble that is dislocated by heavy waves can be easily repaired without having to replace the entire structure. Some aquatic creatures use breakwaters as a habitat, and fixed breakwaters that are placed with open segments allow free movement of aquatic wildlife.
Credits:http://www.ehow.com/list_6830350_pros-cons-breakwaters.html
Credits:http://www.ehow.com/list_6830350_pros-cons-breakwaters.html
sentosa breakwater
Two new breakwaters have been built at Siloso beach, on the southwest shore of Sentosa island. They will serve to protect the beach there, as erosion has been accelerated by the wash from the high-speed ferries plying between the nearby World Trade Centre and the Riau islands of Indonesia. At almost a kilometre in length, Siloso beach is the longest of three artificial beaches built at a cost of $20 million in 1991. The new breakwaters cost more than $1 million. They are each eighty metres long and are placed about a hundred metres offshore.
Breakwaters are only needed at Siloso Beach and along the East Coast Park because elsewhere in
Singapore, longshore drift is negligible.
How is the Breakwaters form:
The breakwaters may be small structures, made of granites and placed one to three hundred feet offshore in relatively shallow water, designed to protect a gently sloping beach
When oncoming waves hit these breakwaters, their erosive power is concentrated on these
structures some distance away from the coast. In this way, there is an area of slack water behind
the breakwaters, which thus will reduce erosion.
Limitations of the Breakwaters:
When the breakwaters deflect the incoming waves before they reach the shore, these
waves that are deflected to other places (exposed areas of the coast) causing erosion.
Breakwaters are unable to provide complete protection for the whole coast and therefore
unprotected areas will prone to erosion.
Breakwaters are only needed at Siloso Beach and along the East Coast Park because elsewhere in
Singapore, longshore drift is negligible.
How is the Breakwaters form:
The breakwaters may be small structures, made of granites and placed one to three hundred feet offshore in relatively shallow water, designed to protect a gently sloping beach
When oncoming waves hit these breakwaters, their erosive power is concentrated on these
structures some distance away from the coast. In this way, there is an area of slack water behind
the breakwaters, which thus will reduce erosion.
Limitations of the Breakwaters:
When the breakwaters deflect the incoming waves before they reach the shore, these
waves that are deflected to other places (exposed areas of the coast) causing erosion.
Breakwaters are unable to provide complete protection for the whole coast and therefore
unprotected areas will prone to erosion.
Types of breakwater structures
A breakwater is constructed some distance away from the coast or built with one end linked to the coast. Breakwaters may be either fixed or floating: the choice depends on normal water depth and tidal range. A breakwater structure is designed to absorb the energy of the waves that hit it. This is done either by using mass or by using a revetment slope (e.g. with rock or concrete armour units).
Caisson breakwaters typically have vertical sides and are usually used where it is desirable to berth one or more vessels on the inner face of the breakwater. They use the mass of the caisson and the fill within it to resist the overturning forces applied by waves hitting them. They are relatively expensive to construct in shallow water, but in deeper sites they can offer a significant saving over revetment breakwaters.
Rubble mound breakwaters use the voids in the structure to dissipate the wave energy. Rock or concrete armour units on the outside of the structure absorb most of the energy, while gravels or sands are used to prevent the wave energy continuing through the breakwater core. The slopes of the revetment are typically between 1:1 and 1:2, depending upon the materials used. In shallow water revetment breakwaters are usually relatively cheap, but as water depth increases, the material requirements, and hence costs, increase significantly.
Caisson breakwaters typically have vertical sides and are usually used where it is desirable to berth one or more vessels on the inner face of the breakwater. They use the mass of the caisson and the fill within it to resist the overturning forces applied by waves hitting them. They are relatively expensive to construct in shallow water, but in deeper sites they can offer a significant saving over revetment breakwaters.
Rubble mound breakwaters use the voids in the structure to dissipate the wave energy. Rock or concrete armour units on the outside of the structure absorb most of the energy, while gravels or sands are used to prevent the wave energy continuing through the breakwater core. The slopes of the revetment are typically between 1:1 and 1:2, depending upon the materials used. In shallow water revetment breakwaters are usually relatively cheap, but as water depth increases, the material requirements, and hence costs, increase significantly.
Credits:
http://en.wikipedia.org/wiki/Breakwater_(structure)
purposes on breakwaters
Offshore breakwaters, also called bulkheads, reduce the intensity of wave action in inshore waters and thereby reduce coastal erosion. They are constructed some distance away from the coast or built with one end linked to the coast. The breakwaters may be small structures, placed one to three hundred feet offshore in relatively shallow water, designed to protect a gently sloping beach. Breakwaters may be either fixed or floating: the choice depends on normal water depth and tidal range. They are made of large pieces of concrete and are spaced about 50m from each other. Breakwater construction is usually parallel or perpendicular to the coast to maintain tranquility condition in the port. Most of Breakwater construction depends upon wave approach and considering some other environmental parameters
When oncoming waves hit these breakwaters, their erosive power is concentrated on these structures some distance away from the coast. In this way, there is an area of slack water behind the breakwaters. Deposition occurring in these waters and beaches can be built up or extended in these waters. However, nearby unprotected sections of the beaches do not receive fresh supplies of sediments and may gradually shrink due to erosion, namely long shore drift.
Breakwaters are subject to damage, and overtopping by big storms can lead to problems of drainage of water that gets behind them. The wall also serves to encourage erosion of beach deposits from the foot of the wall and can increase long shore sediment transport.
Credits:
http://en.wikipedia.org/wiki/Breakwater_(structure)
When oncoming waves hit these breakwaters, their erosive power is concentrated on these structures some distance away from the coast. In this way, there is an area of slack water behind the breakwaters. Deposition occurring in these waters and beaches can be built up or extended in these waters. However, nearby unprotected sections of the beaches do not receive fresh supplies of sediments and may gradually shrink due to erosion, namely long shore drift.
Breakwaters are subject to damage, and overtopping by big storms can lead to problems of drainage of water that gets behind them. The wall also serves to encourage erosion of beach deposits from the foot of the wall and can increase long shore sediment transport.
Credits:
http://en.wikipedia.org/wiki/Breakwater_(structure)
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