13.11.2 How can a coast be managed? Understanding physical processes and human activities is key to reducing changes to coastal landscapes. While we can’t change natural forces like wind or waves, we can manage sand movement and use barriers to protect infrastructure. Coastal management involves hard engineering (such as building sea walls and groynes) and soft engineering approaches. Hard engineering can sometimes cause further issues, as seen in Seabird, Western Australia, where a sea wall stopped sand replenishment and led to beach loss. Soft engineering, such as dune revegetation by the Shire of Gingin, offers more sustainable solutions. Planting grasses and shrubs stabilises dunes by binding sand, which prevents erosion.
CASESTUDY Managing Adelaide’s living beaches
The problem: Adelaide’s sandy beaches face constant erosion ( FIGURE5 ). For 7000 years, south Adelaide’s beaches have eroded, with south-west winds driving the material northwards. This longshore drift has formed a peninsula and dune system in North Haven. For 30 years, sand has been trucked in to replenish southern beaches. The goal is to find a more cost-effective way to manage Adelaide’s beaches.
FIGURE5 The movement of sand northwards along the Adelaide Metropolitan coastline
Adelaide coastline last 7000 years
Key
BP= before present
Natural sand movement
0 years BP
Outer Harbor
Addition of sand has moved the beach and peninsula northward during the last 7000 years
2000 years BP
North Haven
5000 years BP
150 000 m³ per year
Semaphore
6000 years BP
7000 years BP
Sand supply from seagrass die-off approximately 100 000 m³ per year
Major sand movement northward
ADELAIDE
Torrens and Sturt Flood Plain
West Beach
30 000–40 000 m³ per year
Original lagoon and coastal swamp behind coastal dune barrier
Original beach ridge 7000 years BP
40 000–60 000 m³ per year
Brighton
200 000 m³ every two years by dredging
Present coastline
5000–10 000 m³ per year
Predominant erosion during last 7000 years
GULF ST VINCENT
Port Stanvac
0
10
20km
0
10
20km
Source: Spatial Vision
The solution : Adelaide’s Living Beaches Strategy ( FIGURE6 ) involves recycling sand from north to south using a pipeline instead of trucks to transport the sand. The pipeline will extend along the coast, sending sand to the southern end of the beach ( FIGURE6b ). Structures like breakwaters and groynes will be built to trap sand at key locations, further reducing the need for trucks and lowering beach restoration costs.
TOPIC13 Landforms and landscapes – diversity, significance and management 339
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