Hard Engineering Methods
Gabions: As you can see in figure 1, gabbing are cages formed by wire with large stones and rocks. They act as a riverbank linings in wet land structures.
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Figure 1: Gabions In Australia, adjacent to the sea.
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Location in Australia: Newcastle
Newcastle Council has recently completed a capital works project to stabilise the headland at the northern end of Bar Beach, south of Newcastle. The civil construction works was undertaken by local company, Michilis Constructions and the substantial gabion portion of the works, consisting of several walls, was subcontracted to Prospect Contractors from South Australia.
The natural appearance of the exposed rock is aesthetically pleasing and its inherent durability and flexibility were the main factors in the selection of rock filled gabions as the preferred wall type.
The gabions were assembled by Prospect Contractors using a pneumatic lacing tool which saved significant time and cost compared to the traditional continuous lacing wire procedure. Rocks with select facing were used to create an aesthetically pleasing profile whilst PVC coated gabions were selected due to their excellent long term performance in close proximity to salt water.
The natural appearance of the exposed rock is aesthetically pleasing and its inherent durability and flexibility were the main factors in the selection of rock filled gabions as the preferred wall type.
The gabions were assembled by Prospect Contractors using a pneumatic lacing tool which saved significant time and cost compared to the traditional continuous lacing wire procedure. Rocks with select facing were used to create an aesthetically pleasing profile whilst PVC coated gabions were selected due to their excellent long term performance in close proximity to salt water.
Groynes: As shown in figure 2, a gabion is a rigid hydraulic structure built at right angles to the beach to prevent long shore drift. It traps the sediment from longshore drift so that the sediment doesn't shift too far away. They are made of large rocks and stretch out into the sea.
Figure 2: Big and Little Gyrone, Kirra beach, Queensland
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Location in Australia: Maroochy Beach, Queensland
The beaches to the south of the Maroochy River (Maroochydore, Sunshine Coast, Australia) had previously experienced substantial erosion.
This prompted the construction of 4 groynes (with lengths varying between 50 and 100m). ICM undertook the stability calculations and engineering drawings in addition to construction supervision and final certification for Maroochy Shire Council.
The groynes were all constructed using the new 2.5m3 [nominal 4 -5t] sand-filled geotextile containers developed for this project to increase the stability from the previous maximum size of 0.75m3 containers [nominal 1.5t]. Construction was staged, with the first groyne completed in November 2001 and the remaining works completed by May 2003. The works have been very successful at retaining a wide beach and provide additional recreational benefits. On a side note, building groins is not cheap but it has been an effective solution for Maroochy beach due to the effective prevention of erosion. If the government did not step in, they would have lost a lot of tourists, and the land behind would have been in trouble.
This prompted the construction of 4 groynes (with lengths varying between 50 and 100m). ICM undertook the stability calculations and engineering drawings in addition to construction supervision and final certification for Maroochy Shire Council.
The groynes were all constructed using the new 2.5m3 [nominal 4 -5t] sand-filled geotextile containers developed for this project to increase the stability from the previous maximum size of 0.75m3 containers [nominal 1.5t]. Construction was staged, with the first groyne completed in November 2001 and the remaining works completed by May 2003. The works have been very successful at retaining a wide beach and provide additional recreational benefits. On a side note, building groins is not cheap but it has been an effective solution for Maroochy beach due to the effective prevention of erosion. If the government did not step in, they would have lost a lot of tourists, and the land behind would have been in trouble.
Sea Wall: In figure 3 we can see a sea wall, which is a wall or embarkment erected to prevent the sea from encroaching on or eroding an area of land. They are usually built on the edge of a coastline.
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Figure 3: Sea Wall at the Sydney Opera House, Australia
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Rip-Rap: As you can see in figure 4, rip rap is loose stone used to form a foundation to form a foundation for a breakwater of other structure.
![Picture](/uploads/2/0/1/3/20136645/4808035.jpg?325)
Advantages:
- Absorb the energy of waves.
- Allows the build up of a beach.
Disadvantages:
- Can be expensive to obtain and transport the boulders.
- Can be a visual eyesore
- Possibly dangerous for kids
(Figure 4: Rip Rap in Perth, Australia)
Revetments: As shown in figure 5, a revetment is a sloping structures placed on banks or cliffs in such a way as to absorb the energy of incoming water. River or coastal revetments are usually built to preserve the existing uses of the shoreline and to protect the slope, as defense against erosion. For example, a tetrapod (a four-legged concrete structure used as armour on breakwaters. The tetrapod's shape is designed to dissipate the force of incoming waves by allowing water to flow around rather than against it, and to reduce displacement by allowing a random distribution of tetrapods to mutually interlock). |
Figure 5: Revetment in Australia
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