The Victorian Coastal Cliff Assessment - Instability Areas (ASCCIE) is a digital dataset consisting of multiple spatial layer outputs from modelled erosion scenarios. The dataset is recommended for use at the statewide / regional scale along the Victorian coastline. Application of the data should be guided by the accompanying Victorian Coastal Cliff Assessment technical reports and expert advice. The product is not suitable for individual property scale assessments.

ASTaR have been derived based on the geological unit type and cliff height. The methodology for defining ASTaR is

a new method undertaken at a high level and based on the existing cliff height and a defined slope

to identify the possible seaward extent of talus runout. For this state-wide/regional scale assessment, single values were derived for each component. This ‘building-block’ approach (ie: a combination of individual parameters) is expected to produce ‘upper bound’, conservative results, which identifies areas potentially exposed to coastal erosion, cliff instability and cliff slumping/talus

The product is an update to the Victorian Coastal Cliff Assessment, Stage 1. Included datasets for Stage 2a supersede the Stage 1 outputs. The Stage 2a project report should be read in conjunction with the Stage 1 report. Application of the data should be guided by the accompanying "Victorian Coastal Cliff Assessment, Stage 2a technical report" (Tonkin & Taylor 2025) read in conjunction with the Stage 1 technical report, combined with appropriate expert advice.

Planning at regional / state-wide scale

10m

Areas Susceptible to Talus Runout (ASTaR)

Across the Victoria region, several large-scale landslips have been associated with the soft

rock cliff materials. Further to this, there has been a recent fatality due to one of these events.

Consequentially, as part of this assessment, ASTaR at the base of the cliffs have been assessed. A

review of a limited number of areas was undertaken, which identified that the talus runout can

extend as far out from the toe of the cliff as the height of the cliff (a relationship between talus

runout and cliff height of 1:1). Based on the above, a 45° angle has been adopted to be projected from the cliff crest seaward along the profile.

Mapping of the ASCCIE or ASTaR inherently introduces errors due to the mapping method and

resolution. For this assessment transects at 30 m alongshore intervals have been used, with straight

lines interpolating between output points. This could result in jiggered lines when zooming in too

close. Furthermore, the mapping tool does not always accurately identify the cliff toe and cliff crest

as a result of cliff profile/geometry. This is particularly evident for non-cliffs or very gentle slopes.

Some manual edits have been made interpolating between adjacent transects using engineering judgement.

A LiDAR survey of the Victoria region was undertaken between 2006 and 2009 by the Department of

Sustainability and Environment and provides full coverage of the entire Victorian coastline. This

LiDAR was processed into a Digital Elevation Model (DEM) surface and has a grid resolution of 2.5 m

x 2.5 m.

In addition to the 2006-2009 LiDAR, there is more recent higher resolution LiDAR coverage of

localised areas within Victoria. These additional data sets are as follows:

• Victorian Coastal LiDAR Level 3 Classification (Port Phillip Bay & Western Port and East & West

Victoria). This dataset consists of a reprocessed DEM from the original 2006-2007 LiDAR data.

• 2017-2018 Greater Melbourne LiDAR. This dataset consists of 1m DTM (Digital Terrain Model)

of 12,000 km2 of coast across the Greater Melbourne region.

• 2019-2020 Great Ocean Road Elevation and Photography. This dataset consists of a 0.5m grid

resolution DEM.

• 2020-2021 Bayside Yarra LiDAR. This dataset consists of a DEM with data captured at 24

pts/m2.

All of these LiDAR datasets were used in combination for the entire cliffed shoreline, with the highest

resolution and most recent LiDAR data being used for each location. Figure 3.2 shows the LiDAR

dataset extents that have been used for this study.

3.1.2 Coastal transects

In addition to the LiDAR DEMs and DTMs described above, coastal transects were provided by DEECA

for the full length of the Victorian coast. These transects are 400 m long and spaced at 30 m

increments along the shoreline (see example of transects in Figure 3.1). For this project some

transects (e.g. at very high cliffs) have been extended to capture the entire cliff profile.

Further information in the study report "Victorian Coastal Cliff Assessment", Tonkin and Taylor, Sep 2023