Development response to coastal hazards

Natural processes such as erosion and inundation continually shape our diverse and dynamic coastline. When these processes may have a negative impact on environmental, cultural, social, and economic values along the coast, we refer to them as coastal hazards.  Coastal hazard exposure occurs periodically across the coast, and is projected to increase with changes in wave action, storm activity and sea level rise associated with climate change

Clause 13.02-1S requires Council’s to plan for and manage coastal hazard risk and climate change impacts. This requires us to plan for sea level rise of not less than 0.8 metres by 2100 and allow for the combined effects of tides, storm surges, coastal processes and local conditions such as topography and geology when assessing risks and coastal impacts associated with climate change.

What are the coastal hazard risks?

A term to collectively describe physical changes and impacts to the natural environment which are significantly driven by coastal or oceanographic processes. VC171 defines Coastal Hazard to mean "an occurrence of an event within coastal Victoria which includes the individual or combined effects of inundation by the sea, the effects of storm tides, river flooding, coastal erosion, landslip and sand drift which adversely affects or may adversely affect human life, property or aspects of the environment."

Erosion Hazards

Erosion is the loss of sediment from the shoreline because of terrestrial and coastal processes.

The most relevant processes to be considered will be defined by the geomorphic setting and

shoreline class for a given location. The following definitions are adopted from Victoria’s Resilient Coast – Coastal Hazards Extended Guideline (Water Technology, 2022):

  • Short-term erosion (storm bite) is erosion that occurs on a short-term basis, often during a storm. The shoreline and beach then gradually regain sediment (rebuilds). This category of erosion is relevant to Sandy shorelines.
  • Long-term erosion (recession or retreat) is a continuing movement of the shoreline position in a landward direction, occurring either gradually over many years, or when the shoreline does not recover following a short-term erosion event. This category of erosion is relevant to Sandy, Low-earth Scarp, Soft and Hard Rock shoreline classes.

Inundation Hazards

Coastal inundation hazards are typically related to the temporary direct inundation of low-lying land because of overtopping or breaching of dunes, coastal barriers, beach access points or protection works; and/or because of elevated water levels in adjacent waterways from catchment or coastal processes.

  • Storm-tide inundation is caused by a combination of tides, storm-surges, and high wave action during severe weather events, Figure 1.
  • Permanent inundation occurs when low-lying areas are regularly flooded due to the tide. Although not typically a significant issue under current sea level conditions, this type of inundation is likely to having increasing level of impact with sea level rise.

Figure 1 Components of a storm tide event.png

Do I need a CHVRA?

You will be required to provide a Coastal Hazard Vulnerability and Risk Assessment (CHVRA) as part of your planning permit application if your property is identified as being exposed to coastal hazard risks.

You can check if your property is exposed to coastal hazard risks on the Shire’s Online Planning Map. You can use the Address search at the bottom of the map to search for your property. You will see the Climate Change Hazards layers on the left within the layers panel. This shows the areas at risk for both Western Port Bay and Port Phillip Bay.

Click the small plus icon to expand the layers and tick layers off/on to hide/view. Use your mouse wheel to zoom in and out, and hold down the left mouse button and drag to pan.

Coastal-Hazards-GIS-Legend.jpg  

It is recommended that you call Planning Services via (03) 5950 1010 to clarify if your property is exposed to coastal hazard risks and if a CHVRA is required before submitting your application.

Western Port Bay

The State Government’s Western Port Local Coastal Hazard Assessment identifies land exposed to coastal hazards along the Western Port coastline.

It is noted that Council is proposing to apply planning controls in these areas to recognise the coastal hazards formally in the Mornington Peninsula Planning Scheme and ensure associated risks for new development are properly assessed during the planning permit process.

The proposed controls are the Land Subject to Inundation Overlay – schedule 2 to 4 (LSIO2-4) and Erosion Management Overlay- schedule 6 (EMO6). These controls specify the threshold of development that triggers the need for a planning permit and are being introduced by Planning Scheme Amendment C271morn.

You can view the mapping of the LSIO2-4 and EMO6 in the “Planning Information” map on the Shire’s Online Maps. For more information about these controls, visit our Amendment C271morn webpage.

Port Phillip Bay

The State Government’s Port Phillip Bay Coastal Hazard Assessment (2023) identifies land exposed to coastal hazards along the Port Phillip Bay coastline.

It is noted that Council is advocating to the State Government to introduce appropriate planning controls along this coastline to ensure coastal hazards are consistently and transparently assessed during planning permit processes.

 

How can I get a CHVRA?

The CHVRA must be prepared by a specialist with the relevant expertise, such as:

  • A suitably qualified coastal specialist, which is a person with:
    • A relevant qualification in coastal engineering, coastal sciences, geomorphology, and significant relevant professional experience (10 years or more); or
    • A relevant engineering qualification (that is civil, environmental, geotechnical engineering) and significant relevant professional experience (10 years or more).

Additional skills may be required such as flood engineering, ecology, or soil science, however their work must be overseen by the coastal specialist.

If the CHVRA identifies erosion risk to people or property because of landslides caused by coastal processes where the risk is medium or above, then a geotechnical hazard and risk assessment report by a suitably qualified geotechnical engineer or engineering geologist with experience in landslide risk assessment is required.

Where risk treatments (often termed "mitigation measures") are proposed that require the physical construction of works, then the assessment, design, and approval of the works would need to be obtained from the relevant qualified professional e.g., a qualified geotechnical engineer for the assessment and design of slope stabilisation works.

 

What must a CHVRA contain?

All CHVRA's need to consider the following documents:

Marine and Coastal Act 2018

 Marine and Coastal Policy (DELWP, 2020)

 Marine and Coastal Strategy (DELWP, 2022)

 Victoria’s Resilient Coast – Adapting for 2100+ guidelines and supporting documents

 Guidelines for Development in Flood Areas (DELWP, 2019)

 Victorian Floodplain Management Strategy (2016)

 Planning Practice Note 53 (2023) Managing Coastal Hazards and the Coastal Impacts of

Climate Change

 Melbourne Water (2023) Sea level Rise Guidelines – Interim Development Assessment

Principles

 Mornington Peninsula Planning Strategy and Planning Policy Framework with specific

reference to Clause 13.01-1S and 13.01-2S

 Siting and Design Guidelines for Structures on the Victorian Coast (DEWLP, 2020)

 AS 5334-2013: Climate Change Adaptation for Settlements and Infrastructure

 Western Port Local Coastal Hazard Assessment (Water Technology, 2014)

 Mapping outputs from the Western Port Local Coastal Hazard Assessment and subsequent

inundation modelling by Melbourne Water)

These documents and guidance material may change over time, and the most recent and relevant information should be used when undertaking a CHVRA.

 

A CHVRA is a risk management process that provides a structured approach to the management of risk. This is the approach outlined in AS/NZS 5334-2013 “Climate change adaptation for settlements and infrastructure - A risk-based approach”. The risk framework for CHVRA is as shown in Figure 2 below comprised of the following main elements:

  1. Identify the Hazard - starting with defining the geomorphic setting, the coastal drivers and processes of change and the specific requirements of the relevant Overlay (LSIO2-4 or EMO6). Then characterise the specific hazard being considered by the CHVRA – for example, what type of erosion hazard(s) are relevant to the location.
  2. Evaluate Exposure to the Hazard - defining the spatial extent of the hazard. It also includes determining when such hazards might occur and/or provides an estimate of the annual probability (i.e., likelihood).
  3. Consequence Analysis - determines the level impact of consequence from a hazard assuming it occurs. When undertaking a coastal hazard assessment this includes an estimation of exposure and sensitivity of an element at risk. When combined with adaptive capacity then is then termed vulnerability and is a measure of consequence in broader risk assessment terminology.
  4. Risk Estimation - the combination of the likelihood of a particular hazard occurring and the consequence gives an estimate of risk for the asset or people being considered.
  5. Risk Evaluation – is the process by which estimates of risk levels are compared against an organisation’s criterion for risk acceptance. As such, risk may be deemed either acceptable, tolerable, or unacceptable.
  6. Risk Mitigation and Control - is the process of managing the risk through treatment or mitigation actions to achieve one of the following options: avoid the risks, reduce the likelihood, reduce consequences, transfer the risk, or accept the risk. The Marine and Coastal Policy (2020) outlines the hierarchy of adaptation options to consider when looking to mitigate or control coastal risks.

Figure 2 risk framework for CHVRA.png

For further information, including datasets, please refer to the Guidelines FINAL CHVRA Guidelines August 2024 (PDF, 4MB).pdf.

 

What happens once a CHVRA is completed?

There are two levels of CHVRA reports:

  • Basic – is required for all applications and involves:
    • Assemble relevant data.
    • Desktop review and evaluation of coastal erosion & inundation hazards relevant to the specific shoreline class based on most recent detailed coastal hazard investigations or mapping if available.
    • Risk assessment and evaluations including identification of risk treatment requirements and risk re-evaluation.
  • Detailed – additional layer of assessment required where risks to life or property are medium or higher through the Basic CHVRA. Additional assessment includes:
  • Refinement of the coastal hazard exposure estimates based on detailed modelling and analysis applying best practice methods of assessment for the local geomorphology, coastal processes, and oceanographic conditions. All detailed analysis should follow the requirements of the Victoria's Resilient Coast – Coastal Hazards Extended Guideline. The flood levels and floor level requirements as set by of Melbourne Water should also be confirmed.
  • Where risk due to landslides is identified as medium or above the specific hazard analysis and risk assessment approach as outlined in the Guideline for landslide susceptibility, hazard and risk zoning for land use planning (AGS (2007a)) is required.
  • A detailed CHVRA must include a peer review (at the applicant’s expense) and address the outcomes of the peer review.

Below is an outline of the process:

Process CHVRA.png

What are the risk tolerance levels for proposed developments?

Flood/Inundation

  • Where the flood depth exceeds the H2 threshold values (refer to table below) as detailed in Guidelines for Development in Flood Affected Areas (DELWP, 2019) Council will define the flood safety risk as Not Acceptable.

table.png

  • Any floor levels set below the FFL as specified by Melbourne Water or less than +0.6m above the 1% AEP flood level at 2100, if no FFL has been specified by Melbourne Water, will be deemed Not Acceptable.

Erosion Risk

Table 1 – Erosion risk to Property (damage) tolerance levels for Mornington Peninsula Shire Council

table 1.png

Table  2 – Erosion risk to life (safety) tolerance levels for Mornington Peninsula Shire Council

table2.png

 

 

Further information

For further, including datasets, please refer to the Guidelines Coastal Hazard Vulnerability Risk Assessment Guidelines MPS 2024(PDF, 4MB).pdf.

Contact Planning Services Team 5950 1010 

Email - planning@mornpen.vic.gov.au