Coasts and Oceans Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Australian State of the Environment Committee, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06751 5
Coastal settlement and development (continued)
Erosion of beaches and dunes
The movement of sand is a natural feature of beaches. Beaches can be described as eroding (losing sand and foredunes) or accreting (gaining sand). The frequency and severity of cyclonic or storm events and seasonal weather patterns can result in fluctuations of beach width and slope.
The causes of erosion can be classified as follows (Tomlinson 2001):
- short-term natural variability - beach fluctuations, storms,
- medium-term natural variability - periodic changes in coastal climate and beach conditions,
- medium-term erosion - disruption to local sediment budget due to people's activities, or
- long-term natural variability - sea level rise, geological realignment, reduction in sediment supply.
Where development has occurred, property and infrastructure integrity can be threatened by landward movement of the erosion. The south-east Queensland - northern New South Wales coastline has been greatly developed since the mid 1970s but has not experienced a significant erosion event similar to the 1967 event that caused five houses to collapse into the sea on the Gold Coast.
Structures designed to reduce the extent of beach erosion can sometimes result in the opposite effects; that is, increased erosion, either on the beach or on an adjacent stretch of coastline. Similarly, the increasing popularity of offshore undersea barriers to create surfing waves or to dissipate wave energy from sensitive beaches will have ecological impacts that have yet to be determined.
It should be an objective of any coastal management plan for an area such as the Gold Coast to proactively mitigate any erosion caused by groynes and retaining walls (Tomlinson 2001). It should also be an objective to enhance the capability of the natural system to respond to natural sand movement by encouraging dune rehabilitation, for example. However, long-term studies to assess the effectiveness of coastal management strategies are hard to find.