The Australian coastline extends approximately 34,000 kilometres, with many sections being managed by the relevant local councils. Coastline management is a complex undertaking, with proactive steps required to keep our coastlines healthy and intact for future generations.
The Victorian Department of Energy, Environment and Climate Action (DEECA) Tonkin + Taylor have come together for an innovative study of Victoria’s coastline, focusing on the proactive management of coastal cliffs. Coastal cliffs are dynamic by nature, constantly eroding due to natural processes such as wind and wave action, drainage and overland flow, and chemical weathering. The distinctive features of the Victorian coastline are created by the complex interaction between the various geological units and coastal processes to create landforms that support a diversity of cultural, environmental, social, and economic values.
However, accelerated climate change, including the consequent rise in sea levels, poses a significant risk to coastal cliffs and their associated ecosystems and infrastructure. Proactive risk management is therefore essential to ensure these natural and man-made coastal assets can be enjoyed by future generations.
After a competitive tendering process, Tonkin + Taylor was selected by DEECA to undertake a study of coastal cliffs along the entire Victorian coastline.
The purpose of the study was to provide an understanding of coastal risks at a regional level, to support local land managers in undertaking their role, and to identify areas requiring detailed local assessments. Tonkin + Taylor’s skilled team of coastal engineers and engineering geologists brought extensive experience to this complex project.
The team assessed various geological units and coastal processes to determine cliff areas susceptible to inundation and erosion, as well as talus runout, in the even that instability occurred. Melbourne-based Tonkin + Taylor Associate Engineering Geologist Wendy Greatbatch helped lead the cliff instability assessment work.
“Projects like this, where you are dealing with a wide range of geologies and considering the effects on a regional scale, are very rare, and make for a very exciting project,” said Ms. Greatbatch. With an understanding of the Victorian geological units and their weathering behaviour, Ms. Greatbatch divided the coastline into areas with similar responses to coastal processes, validated through a series of “ground-truthing” site visits.
The study included complex GIS analysis of historic and recent aerial imagery, augmented by aerial reconnaissance of the entire coastline. Reconnaissance by a small fixed-wing aircraft provided additional detail on coastal processes, allowed further validation of the assessment approach, and provided DEECA with a repository of thousands of up-to-date high-resolution images, at a scale not previously available.
By combining disparate information from multiple sources, Tonkin + Taylor assessed past, present and future erosion rates under different sea-level scenarios. The information was then used to inform a “second-pass” risk assessment focused on public assets and safety.
This work by Tonkin + Taylor provides a valuable building block on which future detailed studies at a local scale can be undertaken, as well as providing a record of the current coastal cliff conditions at a scale not previously available. The work is intended to help land managers engage with their local community and to proactively manage their unique coastal assets.
For more information about Tonkin + Taylors geotechnical engineering capabilities, visit www.tonkintaylor.com.au.
Image: Darryl Leach/shutterstock.com
