Department for Envi ronment and Heri tage Adelai de’s Living Beaches A Strategy for 2005 – 2025 Coastli ne No. 35 December 2005 www.envi ronment.sa.gov.au 0013_28pp_StrategySummary 1 23/12/05 10:42:28 AM Seacliff (Johnny Kamma) All information in this report was correct at the time of printing. Except where otherwise indicated, all figures and photographs have been provided by the Department for Environment and Heritage. All volumes of sand quoted in this report are compacted volumes, i.e. volumes in situ on the beach. When sand is loaded into trucks, the volume increases by approximately 30%. Cover photo: Brighton 0013_28pp_StrategySummary 2 23/12/05 10:42:46 AM Brighton jetty West Beach (Johnny Kamma) Contents 2 Foreword 3 Summary 4 Factors affecting the Adelaide coast 4 Wind and waves 4 Coastal development 4 Stormwater and wastewater discharges 4 Seagrass loss and seabed instability 5 Sea level rise 6 Coast protection methods used to date 6 Beach replenishment 7 Sand trapping 7 Sand bypassing 8 Seawall protection 8 Dune management 9 Alternative management strategies 10 Evaluation of alternative strategies 12 The management strategy for 2005–2025 13 Continue beach replenishment 14 Recycle sand more effectively using sand slurry pumping and pipelines 15 Add coarse sand from external sources 16 Build coastal structures in critical locations 17 Integrate sand bypassing at harbours with beach management 18 Implementation plan 20 Economic, social and environmental considerations 20 Economic assessment 21 Social impacts 22 Environmental impacts 24 Community education and consultation Page 1 – Adelaide’s Living Beaches 0013_28pp_StrategySummary 3 23/12/05 10:43:05 AM Tennyson dunes Brighton beach Foreword Adelaide’s coastline is a special asset and an inspiration to many local residents and visitors. The coastline is dynamic, always Furthermore, the strategy of beach increasing investment in strategic shifting in response to the wind and replenishment, using seawalls as areas of infrastructure. waves. However, human impacts the last line of defence, has been a In the long term, the strategy is have altered the dynamics of the successful and cost-effective method expected to reduce the future cost coast to such an extent that natural for maintaining sandy beaches, of managing the Adelaide coastline processes can no longer sustain rebuilding sand dunes and preventing by about 20%. the beaches. storm damage to property. The community’s views on beach Most of the land behind the This document describes the strategy management have been obtained foreshore was developed from for managing Adelaide’s beaches during extensive consultation over the early 1900s onwards. Roads, from 2005 to 2025, which has been many years, and these have been buildings, houses, recreational areas, developed by the Coast Protection considered in the development of and their sewerage and stormwater Board for the State Government. the strategy. Indeed, one of the infrastructure were often built right A technical report, enclosed on CD, over coastal dunes. Consequently, has been produced to accompany major benefits of the strategy is dune sand is unable to erode away the strategy. that it will minimise the number of trucks carting sand along Adelaide’s during storms, and so substantial In concert with the Government’s beaches and roads. protection works have been put in Living Coast Strategy (2004), the place to retain the foreshore and beach management strategy for The Coast Protection Board will now beaches. Early on, this protection 2005–2025 continues to manage guide the implementation of the was in the form of seawalls. From erosion risks to metropolitan coastal beach management strategy for the 1970s, however, protection was assets by replenishing beaches and 2005–2025, which was endorsed by mainly achieved by replenishing using structures in critical locations the Government in November 2005. beaches with sand. to slow the northerly drift of sand. In Adelaide’s coastline is now a highly addition, the strategy contains three managed one. The sand that forms important initiatives. The first is to the beaches is a scarce and moving recycle sand more effectively using asset. The future management of pipeline transfer systems. The second the beaches needs to be responsive is to add sand from external sources GRAHAM FOREMAN to changing conditions to ensure to the beach system to counter the Chair, Coast Protection Board that future generations are not ongoing loss of dune volume and disadvantaged by our decisions beach width caused by sea level now. rise and other factors. The third is to It is tempting to think that a integrate sand bypassing at harbours permanent structural solution to with beach management. These the moving sands is preferable to initiatives will contribute to achieving the ongoing recycling of sand from actions listed in South Australia’s north to south. However, the scale Strategic Plan (2004), including and number of structures that would maintaining the lifestyle quality of be needed to achieve this would South Australians, seeking creative be both costly and disfiguring. solutions to environmental issues and Page 2 – Adelaide’s Living Beaches 0013_28pp_StrategySummary 4 23/12/05 10:43:19 AM Beach replenishment at Seacliff, 2004 Summary The Coast Protection Board has been managing Adelaide’s beaches for over 30 years in response to sand eroding and moving north along the coast. The main management actions Other recent developments have The main components of have been to replenish beaches been the construction of the Holdfast the strategy for managing with sand taken from other Shores marina at Glenelg and the Adelaide’s beaches from metropolitan beaches, offshore Adelaide Shores boat haven at 2005 to 2025 or elsewhere, and to build seawalls West Beach. These harbours have as the last line of defence against interrupted much of the northerly 1. Continue beach replenishment – Continue the existing program storms. Without these measures, movement of sand along the of beach replenishment, placing several of Adelaide’s southern coastline. Ongoing bypassing and 160,000 cubic metres of sand each metropolitan beaches would by dredging of significant quantities year at strategic locations on now have very little sand left on of sand and seagrass around the southern and central beaches them and numerous foreshore harbours is now required. to maintain the sandy foreshore, build up dune buffers, and properties would have been In 2000, the Department for protect coastal infrastructure. damaged by storms. Environment and Heritage, on 2. Recycle sand more effectively Even so, the Coast Protection behalf of the Coast Protection using sand slurry pumping and Board recognises the need to Board, initiated a review of the pipelines – Existing sand supplies improve the management strategy, management of Adelaide’s will be recycled more effectively particularly in regard to reducing metropolitan beaches. Based on using sand slurry pumping and pipelines, which will minimise the the number of trucks carting sand examination of the benefits and costs need for trucks to cart sand along along Adelaide’s beaches and of a range of strategies, along with beaches and suburban roads. roads. Moreover, following a major the results of a series of modelling 3. Add coarse sand from external program of offshore dredging at and feasibility studies and input from sources – Coarser, more stable Port Stanvac in the 1990s, historical the community, the Department sand will be added to the system sources of sand have now been has developed this strategy for from external sources such as exhausted. Alternative sources of managing Adelaide’s beaches from Mount Compass to tackle the sand have been investigated as a 2005 to 2025. The strategy will ensure ongoing loss of dune volume and beach width caused by sea matter of urgency to supplement the the long-term viability of the city’s level rise and other factors. existing finite amount of sand within coastal assets by maintaining beach the metropolitan beach system. quality for recreation, amenity and 4. Build coastal structures in critical locations – Structures such as However, the cost of importing sand protection purposes, while reducing groynes and offshore breakwaters from sources outside the beach the impact of replenishment activities may be used in a few critical system has escalated to the point on beach users and coastal residents. locations to slow the northerly that alternative management drift of sand. options have been initiated in 5. Integrate sand bypassing critical locations. For example, a at harbours with beach trial breakwater has been built at management – Integrating sand bypassing requirements Semaphore South to slow sand at harbours with the beach movement. The trial is at an early replenishment program will result stage, but the breakwater is already in more effective recycling of holding sand in the area and sand and reduced harbour performing as expected. management costs. Page 3 – Adelaide’s Living Beaches 0013_28pp_StrategySummary 5 23/12/05 10:43:23 AM Henley Beach, 1953 (State Library) Semaphore Park, 1999 Factors affecting the Adelaide coast The Adelaide coast is a dynamic environment controlled by numerous physical and biological processes. Wind and waves Stormwater and meadow edge can be eroded by waves. This is thought to have The dominant forces affecting wastewater discharges increased the rate of seagrass loss Adelaide’s beaches are the wind With coastal urbanisation comes and made it difficult for plants to and waves, which together set up the necessity for stormwater recolonise the seafloor, even though an overall northward drift of sand infrastructure and sewerage. water quality has been improved. along the coast, although sand Much of Adelaide’s stormwater is Finer-grained sand that was once is also moved in other directions discharged to the coast through trapped by seagrass meadows under different wind conditions. This the Patawalonga, Torrens and Port has been released and washed movement of sand along the coast River systems, as well as via over ashore.