Major Studies and Reports on Adelaide Coast Protection
The 1970 Culver ReportIn early 1965, a University of Adelaide study jointly funded by State and local governments was begun to determine the causes of beach loss and to propose remedies for it. In December 1970, Bob Culver of the Civil Engineering Department of the university presented the report of this study, now known as the Culver Report (1970). It made several important recommendations:
Following proclamation of the Coast Protection Act 1972, the Coast Protection Board was formed. The main protection strategy pursued since then has been beach replenishment in order to provide adequate sand for buffers and beach provision. This has been backed up by using seawalls where necessary as a last line of defence against erosion and storm damage. These seawalls complemented the seawalls constructed before the Coast Protection Act by councils and the Marine and Harbors Agency. The strategy also included stabilisation of dunes from wind-blown sand drift with vegetation and fencing. The 1984 Adelaide Coast Protection Strategy ReviewThe 1984 Adelaide Coast Protection Strategy Review by the Coastal Management Branch reviewed the rock protection and beach replenishment strategy adopted following the Culver Report and all practical alternative strategies:
After a cost analysis of these options in alternative combinations, the main recommendation of the 1984 review was to continue beach replenishment and to replace existing seawalls only where adequate beach protection could not be provided by replenishment. This was considered at the time to be the most effective and least costly way of maintaining the beaches and protecting development until an adequate offshore sand supply could be found. 1984 Review (4.8Mb PDF) (Please note that this is a large file and may take some time to download.) The 1985 Metropolitan Coast Protection District Management PlanThe 1985 Metropolitan Coast Protection District Management Plan is one of five Coast Protection Board district management plans for the South Australian coastline. It covers the coastal area (as defined in the Coast Protection Act) from Port Gawler in the north to Sellicks Beach in the south. The plan included the following policy commitments:
The Board recommended careful consideration of all construction, whether it be buildings, roads or engineering structures such as seawalls, in beach and sand dune areas. The potential for structures to interfere with natural processes, aesthetics and public access was high, and this, together with a risk of damage to the structure itself, indicated that siting and design were more critical than in inland areas. The Board considered that in many cases development should be prohibited. The 1992 Review of Alternatives for the Adelaide Metropolitan Beach Replenishment StrategySince the review in 1984, the Coastal Management Branch had been able to investigate beach replenishment sand sources, particularly those offshore, in more detail and collect better data on sand movement along the metropolitan coast. The Branch was able to better represent the metropolitan beach system in terms of volumes of sand movements, rates of movements, identification of erosion and accretion zones, anomalous behaviour along the coast, onshore/offshore movements and other aspects of the beach system. It was found that up to 160,000 cubic metres of beach replenishment sand was required annually in order to maintain beaches to 1977 levels. Sampling and underwater investigations of offshore beach replenishment sources were greatly assisted by trial dredging operations carried out from 1989 to 1991. Between 1988 and 1990, around 190,000 cubic metres of sand was trucked from Torrens Island to Glenelg North and 100,000 cubic metres of sand was pumped ashore at North Haven by a suction dredge and trucked to Somerton. In 1990, the Coast Protection Board recommended a trial dredging program to reduce the amount of sand carting by trucks. Government funding allowed Australian Dredging and General Works Pty Ltd to dredge approximately 100,000 cubic metres of sand from an offshore sand source at North Haven using a small split hopper trailing suction dredge called the Pelican. The dredged sand was pumped ashore through a pipeline to the beach at Glenelg North. A further dredging trial in 1991 saw Australian Dredging and General Works dredge 200,000 cubic metres of sand from an offshore source at Port Stanvac. In view of this information, particularly the opportunity to provide sand to the beaches by dredging offshore sources, it was considered time to reassess the beach replenishment strategy and update the 1984 review of the methods available to achieve the required level of protection for the Adelaide coast. Eight strategies were considered in the 1992 review, several similar to those outlined in the 1984 review but using updated information and costings for their assessment:
Each alternative was costed over a 20-year period to determine the most cost-efficient strategy for maintaining the metropolitan beaches. The status quo strategy was found to be the least costly, and would provide for no further loss of beach amenity and maintain beach levels. Construction of seawalls was the next most cost-efficient strategy but over the long-term would lead to sand erosion and loss of beach amenity. The increased replenishment strategy would provide for improved beaches but was 40% more expensive than the status quo strategy. The progressive construction of groynes strategy represented a significant visual intrusion and was 60% more costly than the status quo strategy. In addition, while major replenishment by dredge was more cost-effective than major replenishment by pipeline, it was still nearly 100% more costly than the status quo strategy. The Coast Protection Board recommended that $2.5 million be allocated in the 1992–93 capital works budget for beach replenishment and thereafter for every 2-year period until the offshore sand source at Port Stanvac was depleted, and then an ongoing commitment of approximately $2.9 million biennially for the remainder of the 20-year period, based on 1991 present day costs. The funding would enable 200,000 cubic metres of sand to be dredged and pumped ashore from an offshore sand source, and some remedial beach replenishment at localised erosion zones along the metropolitan coast. This was in accordance with the Board's protection strategy for the metropolitan coast. The Board considered this the most cost-efficient minimum ongoing replenishment necessary to maintain the beaches in their condition and to provide adequate protection against storm damage. The replenishment strategy adopted was the most cost-efficient means of recovering offshore sand sources. However, dredging costs were approximately 2.5 times more expensive than previously used trucking methods. As the Minister for Environment and Planning announced when the dredging method was being trialled in 1989, the benefits over trucking were elimination of damage to roads and noise in residential areas, and minimisation of conflict between trucks and beach users. Coastal councils and local residents showed enthusiastic support and preference for the dredging method. A further benefit was that the source of the sand was not naturally available to the existing beach system. The current metropolitan beach sand source was finite and diminishing due to natural losses and ongoing sea level rise. The offshore source was generally better quality sand and provided a new injection of sand without jeopardising the beaches from which sand was taken in the past. The 1997 Report of the Review of the Management of Adelaide Metropolitan BeachesIn 1997 a reference group was appointed by the then Minister of Environment and Natural Resources, the Hon. David Wotton, to conduct a public inquiry into the management of Adelaide's beaches from Port Noarlunga to North Haven. The reference group considered that beach replenishment was the most appropriate strategy for managing the Adelaide coast between Kingston Park and Semaphore. The group recommended that maintaining beach quality for recreation and amenity should be given due regard in future coastal protection programs. The group also recommended that alternative sources of sand be investigated as a matter of urgency to supplement the existing finite amount of sand within the metropolitan beach system. Of immediate concern to the reference group was the erosion at Semaphore Park and the associated loss of amenity and risk to property. Ten years of sand carting had not provided a long-term solution to the erosion problem in that area and alternative protection measures needed to be considered. A plan for protection of the area with a field of breakwaters was initiated, with construction of a trial breakwater at Point Malcolm starting in 2003 and being completed in February 2005. The trial is at an early stage but the breakwater is already holding sand in the area and performing as expected. For more information see Semaphore Park Foreshore Protection Strategy. Since the 1997 review, the Coast Protection Board has carried out a range of offshore and land-based sand source investigations. A large reserve of suitable sand has been identified in the Mount Compass area, estimated to be sufficient to supply Adelaide's beaches for hundreds of years at current replenishment rates. However, the need for washing to remove clay and the supply costs for sand from Mount Compass are much higher than for sand from within Adelaide's beach system. Cover, Introductory Diagrams
and Table of Contents (450Kb PDF) Latest Review of Adelaide Beach ManagementIn 2000, the Department for Environment and Heritage, on behalf of the Coast Protection Board, initiated a review of the management of Adelaide's metropolitan beaches. During the review, the Department considered a range of alternative coast protection strategies. Most of these alternatives had been examined in previous studies in 1970, 1984, 1992 and 1997. However, all alternatives were reassessed in light of the recent changes to the coast and the results of updated coastal process modelling data commissioned by the Board during the review. For more information see Alternative Management Strategies. Based on examination of the benefits and costs of all alternatives, along with the results of a series of modelling and feasibility studies and input from the community, the Department has developed an innovative strategy for managing Adelaide's beaches called Adelaide's Living Beaches: A Strategy for 2005–2025. Details of the latest review of Adelaide beach management are contained in the Adelaide's Living Beaches: A Strategy for 2005–2025 technical report, which is available on CD-ROM by contacting the Coastal Protection Branch (see Information Resources). Coastal Processes StudyIn April 2003 the Coast Protection Board commissioned Coastal Engineering Solutions Pty Ltd to update coastal process modelling for the metropolitan coastline from Kingston Park to Outer Harbor, to provide technical support for the latest review of Adelaide beach management. The study took into account possible future changes to seagrass meadows and sea levels (as a consequence of climate change), as these have the ability to alter nearshore wave conditions and thus the amount of sand being transported along the coast. The coastal reach in the vicinity of Hallett Cove was also included in the study area to investigate a possible strategy of exploiting the predominant northerly sand transport processes to naturally supply sand to the downdrift metropolitan beaches while improving beach amenity at Hallett Cove. As well as addressing the existing situation, the study included modelling of the processes affecting the beaches as they might have been 100 years ago and are likely to be in 20, 50 and 100 years time. The last three scenarios have obviously made progressively larger assumptions about how the coast and climate will change. Sea level rise predictions are the mid-range of the current modelled predictions by the Intergovernmental Panel on Climate Change in 2001 (see the IPCC Third Assessment Report: http://www.grida.no/climate/ipcc_tar/). Main findings of the coastal processes study (150Kb PDF) Seagrass Rehabilitation StudiesIn 2001, SARDI Aquatic Sciences and the Coastal Protection Branch of the Department for Environment and Heritage held Australia's first workshop on seagrass restoration to review the current status and knowledge in Australia and overseas. Following the seagrass restoration workshop a program for seagrass rehabilitation was formulated, with the ultimate objective to develop reliable techniques for seagrass restoration and rehabilitation suitable for application along the Adelaide metropolitan coast. Three approaches to seagrass restoration have been or are currently being investigated:
During 2002 and 2003 work focused on donor-dependent and independent methods, but current research is predominantly directed towards recruitment facilitation. Most successful is the use of hessian material to boost natural recruitment of Amphibolis antarctica juveniles. Trial sites are located at Henley Beach and Tennyson. Seedlings are being monitored for survival and growth. If the trials prove successful, then artificial stabilisation of the seabed to assist seagrass regrowth could be contemplated. This approach not only avoids damaging existing seagrass meadows but also appears to be less time-consuming than the propagation and planting of seagrass seedlings. Notwithstanding this, research into the use of seedlings in seagrass restoration is ongoing. New seagrass meadows would provide habitat and protect marine life, which could restore a substantial ecology that has been lost off the Adelaide coast. However, it would be many centuries before seabed levels are restored by this means. Therefore, the exacerbated foreshore erosion due to seagrass loss will only partially be reduced. This reduction would be due solely to the increase in seabed friction on wave energy from the seagrass meadows. For more information see the South Australian Research and Development Institute (SARDI) website: http://www.sardi.sa.gov.au Beach Values StudyThe beach values study carried out by Burgan in 2003 quantified the value of beaches to foreshore property owners and the public. Records of historic storm damage give an indication of the value of beaches to protect not only houses but also foreshore infrastructure including roads, services and public amenities. These values would be lost or significantly reduced where beaches are not prevented from drifting away. The basic results are contained in the table below.
Beach Values Study Final Report (200Kb PDF) Beach Users StudyIn 2003, the Department for Environment and Heritage commissioned a study by McGregor Tan Research to determine how the community uses the beach, the value of particular beach attributes, and attitudes towards different beach management strategies. A clean beach, a clean ocean and having sandy beaches were considered valuable by a large proportion of respondents. Beach replenishment received the most support in terms of different management strategies, because it was generally perceived to be the most effective and least intrusive method. Pipelines were suggested by some participants as an effective way of maintaining sand on the beaches while minimising social impacts. Beach Users Study Summary Report (500Kb PDF) Recreational Beach Width for Adelaide's Metropolitan BeachesIn 2005, recreational beach widths were calculated for each profile location along the metropolitan coast. Results were compared with data obtained in previous years to reveal long- and short-term trends in beach erosion or accretion. The major finding of the study was that the beach replenishment program has successfully increased the width of the beach in several critical areas along the metropolitan coastline. Coastline 36 – Recreational Beach Widths along the Adelaide Coastline (1.1Mb PDF) Technical Report – Recreational Beach Width for Adelaide's Metropolitan Beaches (1.1 Mb PDF) Appendix A – Changes in recreational beach width at each profile location over time (1.1 Mb PDF) Information ResourcesCopies of many studies and reports on Adelaide coast protection are available by contacting the Coastal Protection Branch on (08) 8124 4877 or by email: Carole Hutchens. |
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