Case Study: The Port Campbell coast
The Port Campbell Coast, is famous throughout Australia for its scenic beauty. Its management is concerned with minimising the impact of the many visitors seeking to enjoy the views of the cliffs, stacks, caves, and arches.
The cliffed coast from Cape Otway to Port Campbell and on to Warruambool is famous for its scenic beauty (see figure 2.9(1)): the Great Ocean Road undulates close to the clifftop for more than a hundred kilometres, taking in a succession of wide panoramic views.
Geologically, the cliffs are cut into the Port Campbell Limestone, a yellowish brown calcareous clay and limestone capped by the thin, dark Hesse Clay. Typically the cliffs rise vertically 40-80 m from an energetic wave zone, and offshore stacks, reefs and arches are features of a striking scenic coastline. The cliffs face south-west, directly into the swell and storms of the Southern Ocean, which are only slightly reduced in energy by the narrow continental shelf. The cliffs truncate an undulating coastal plain, and in places valleys have been left 'hanging' by the rapid recession of the shoreline, estimated by Bird (1993) to average 17 cm/year. Many cliffs have a top of bare soil for a few metres from the edge, eroded by wind and spray down to the limestone. This is backed by a low (< 2 m) bluff in Hesse Clay. The clay soils are also vulnerable to foot traffic and gully erosion; in places runoff in the past from the coast road has cut deep trenches into the slope to the cliff.
The long, spectacular coastline is dominated by one major use – car-based scenic tourism. From the Great Ocean Road, short feeder roads lead to defined car parks, thence fenced walkways to lookouts. Management is based on access control and interpretive signs. Vegetation loss, packed topsoil and gullying are the clear impacts of past uncontrolled foot traffic, now much reduced by active management.
In many parts of Australia the scenic values of cliffed coastlines have been compromised by building close to edges or ridgetops, thus encroaching on skyline and horizon views. This is not the case along the Port Campbell coast, where public ownership has averted the problem. The coastline is almost entirely within the Port Campbell National Park, which is managed by Parks Victoria.
Several issues need to be addressed in the management of cliff and shore platfonn areas. Many cliffs and shore platforms are significant habitat in Australia; often they have been protected by their inaccessibility. Small crustaceans, molluscs and various algae may survive on platforms that are rarely visited, but are quickly depopulated by collecting and disturbance. Nesting sites and rare plant species clinging to steep cliff refuges may be lost in one
Figure 2.45 Cracking in cliff top, Hallett Cove, South Australia. This cliff is hard, partly metamorphosed, sedimentary rocks. It began to collapse, following several days of heavy rain, at locations where stormwater was discharged to the top of the cliff. The local council decided to repurchase four houses earlier approved for development, including the one shown here
(photography Nick Harvey)
season of sheep grazing. These pressures are not readily perceived, but constitute an ongoing challenge to coastal management in Australia, in recording, monitoring and protecting.
Everywhere cliff erosion has the potential to be a management issue. Longterm natural erosion is to be expected on steep areas that are subject to temperature changes, water flow and seepage (see figure 2.45). Many human activities can exacerbate the erosion or make it a matter of concern. Pedestrian traffic on cliff footpaths in unstable rock can accelerate erosion by orders of magnitude, as can vegetation removal through grazing. Stormwater that is allowed to run over clifftops may destabilise even apparently resistant cliffs.
Decisions to zone sites for development that are later found to be unstable can prove a very costly process for governments too ready to respond to the demand for houses with a wide coastal view. Likewise, engineering works to stabilise cliffs or to protect the eroding toe of a cliff are usually very expensive. Natural erosion of cliffs may proceed episodically, with cliffs that have been apparently stable for decades becoming locally mobile after a long period of exceptionally heavy rain that coincides with a very high tide. Such an episodic, irregular process may encourage a perception of stability in places where a cautious management approach, such as the use of buffer zones or special building foundation regulations, is more appropriate.
The collapse of easily undermined strata, such as aeolianite, raises safety and liability issues for coastal managers, especially where such places are at the back of well-used recreation beaches, ft can be addressed in a fairly straightforward way using notices or access control, provided there is an awareness of the potential of the problem.
Headlands and cliffs provide some of the most spectacular scenery in Australia; the rugged beauty of headlands form key landmarks as well as being popular viewpoints. The character and visual amenity of such places is critically affected by their management: clearance, inappropriate plantings, poorly located tracks, the intrusion of buildings – particularly in skyline silhouette locations – may have a significance for a wide area. These are places where sensitive planning and landscape architecture can make a particularly significant contribution to the amenity of the coast (see 'Protected coastal areas' in chapter 4).