Title

Cliff Risk Score - Short Term - now to 2040 

Alternate title

cliff_riskscore_shortterm_to_2040 

Purpose

Regional / state-wide scale 

Maintenance and update frequency

As needed  

Title

File geodatabase, shapefile 

Topic category

• Environment
• Oceans

Classification

Unclassified  

Statement

The risk assessment framework defines risk as the “effect of uncertainty on objectives” and utilises likelihood and consequence to determine risk. Where likelihood is the probability of a coastal hazard occurring, and consequence is the impact of the coastal hazard on coastal values and uses, e.g. social, cultural, economic, and environmental. The first step of the risk assessment was the development of hazard extents and likelihoods based on the mapped ASCCIE and ASTaR. Likelihood defines the potential frequency of occurrence of a hazard occurring, and these were mapped to identify areas potentially at risk to cliff instability and/or erosion related to a likelihood. In this assessment a qualitative measure of likelihood was used. Likelihood is divided into five categories: rare, unlikely, possible, likely, almost certain. Each hazard scenario is assigned a particular likelihood and rated on this five-point scale which is considered increasingly likely over the long-term (2070-2100). Professional judgement was used to best define the likelihood of the hazard scenario for each timeframe. It is recognised that there are a range climate change trajectories and uncertainties regarding the impact of climate change on hazards. Note that the GIS exercise undertaken utilised only a single ASCCIE polygon (the most likely) for each timeframe in the analysis. The calculation of risk ratings assumes the same likelihood for each assessed timeframe across all coastal compartments, irrespective of differences in the underlying geology of coastal cliffs across coastal compartments. This limitation of the assessment is tied to the regional scale and deterministic approach adopted in the development of hazard inputs. For a regional/state-wide scale assessment it is not possible to adopt a probabilistic approach due to the large scale, total length of the shoreline and lack of site-specific data to build probability distributions around each parameter. The purpose of this regional/state-wide assessment is to identify high risk areas, where it would be prudent to undertake more detailed, probabilistic assessment on a local-scale or site-specific scale. Further information in the study report "Victorian Coastal Cliff Assessment - Stage 2 - Risk Assessment", Tonkin and Taylor, Sep 2023 

Description

Output derived from ASCCIE and ASTarR modelled datasets 

Use limitation

Unknown 

Classification

Unclassified  

Attribute Quality

Positional Accuracy

Comments

The method utilised to produce the risk ratings presented in this report has delivered an effective overview of risks associated with coastal cliffs at the coastal compartment level. There is potential to further leverage the data underlying the assessment and to refine the outputs of the process for the benefit of end users. The following recommendations should be considered for future further development of risk assessments focused on areas susceptible to coastal instability and erosion hazards within Victoria.  Future third-pass risk assessments building on the second-pass risk assessment framework presented in this report should include a review of risk tolerability thresholds, and the likelihood and consequence criteria used in the calculation of risk ratings. Engagement with local stakeholders should be prioritised to ensure the perspectives and risk tolerance of Traditional Owners and key stakeholders are reflected in risk ratings derived from tertiary risk assessments. Future third-pass risk assessments should also consider additional localised features such as the specific geology of coastal cliffs. 

Conceptual Consistency

Missing Data

Excess Data