FAQ - old

Erosion and flooding are a result of ongoing coastal processes and sea level rise.

Erosion is the result of sand and sediment being moved either offshore or along the shore by waves and currents. It can be a slow seasonal process or it can be sudden, such as after storm events.  Erosion can lead to the loss of public beaches and foreshores, and cause damage to infrastructure, private property, and buildings.

Coastal flooding means the flow of water onto previously dry land. It may either be permanent (for example due to sea level rise) or a temporary occurrence during a storm. Flooding, as a result of storm surge, can cause damage to infrastructure and private property. Permanent inundation, due to sea level rise, can make areas of land unuseable.

A CHRMAP is a Coastal Hazard Risk Management and Adaptation Plan. This is a strategic planning document that informs community and decision makers about the potential hazards, consequences and actions needed to respond to predicted erosion and inundation (flooding). The CHRMAP identifies areas and assets vulnerable to coastal hazards, and develops strategies to respond to changes in a way that considers social, environmental and economic values.

The State Coastal Planning Policy (produced by the Western Australian Planning Commission) requires local governments across the state to prepare CHRMAPs for coastal land under their management.

Adaptation is about changing our towns, beaches and experiences to manage the risk of erosion and flooding. There are four key adaptation options available:

Avoid means identifying future "no build areas" and using planning tools to prevent new development in areas at risk now, or in the future.

Retreat means relocating or abandoning assets that are at risk; ecosystems are allowed to retreat landward as sea levels rise.

Accommodate means continuing to use land in development areas and accommodate risk through raised floor levels, raised roads, etc. This is most relevant for managing temporary flooding.

Interim protection means using hard structures (e.g. groynes and seawalls) or soft treatments (such as sand replenishment and dune management) to protect land from the sea. Engineered structures are designed to withstand certain storm events and have an effective life (such as 50 years) after which they may no longer be effective, therefore are not a permanent solution.

Engineered coastal protection structures have a discrete design life, and do not last forever. They can also have high financial costs, and can impact on the usability and amenity of public foreshores and beaches. Community feedback on the values of Mandurah's northern beaches, and how coastal adaptation should be funded (e.g. who should pay) is important to help make decisions on what adaptation options are viable for the area. 

The coast is a dynamic environment that is continually shaped by coastal processes of erosion and coastal flooding. The CHRMAP will assist the City of Mandurah and the local community to proactively plan for adapting our northern beaches to coastal processes, informed by community values such as use and enjoyment of the coast.

The CHRMAP includes assessment of coastal hazards and risks over time. This may indicate risks to private properties. The CHRMAP will recommend planning and decision making pathways for the City of Mandurah, landowners, and the community to proactively manage those risks over time.

This project supports planning and investment decisions to be made by the City. Managing the impacts of coastal risks will likely require investment of public funds, through rates or tax, therefore everyone in the community will be indirectly affected and has a role in adaptation planning. Keep an eye on this website to find out about opportunities to provide feedback on how you think public funds should be invested in coastal adaptation.

The residential property market is subject to a number of external factors that can influence property values. The City is unable to comment as to whether the release of the CHRMAP will negatively impact the value of properties that have been identified as being at risk over the next 100 years.

These maps do not increase the existing risk status of property. This risk already existed prior to the preparation of these maps and is likely to be already known by insurers. The maps are an information and management tool that provides landowners, the broader community and the City with a clearer indication of areas that may be vulnerable to coastal erosion over various planning timeframes. The City has no control or influence in the calculation of property insurance as this is a matter for private insurers. Home/business owners should ensure they are familiar with their policy and are aware of any risks their policy will not cover.