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The Canute tool enables calculation of potential sea levels for the majority of Australia’s coastline

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We are choosing an example in Tasmania

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A site at St Helens on Tasmania’s east coast will be selected

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This shows the modelled station selected

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This demonstrates selection of a high greenhouse emissions scenario for an asset period of 1 year in 2100.

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This page demonstrates the three page output generated from Canute for the selected site. Note that the blue curves on the output plots are for present day conditions (without factoring in future sea-level rise); the red curves include the impacts of future sea-level rise. Lets consider the second page.

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When we consider an asset at a level of say 1.2m AHD under current conditions (excluding the contributions of wave setup, run-up and other factors) the asset is identified to be likely to be inundated with an exceedance probability less than 0.01 (or 1%). With the incorporation of sea-level rise the exceedance probability of inundation at the same still water level (1.2m AHD) is greater than 0.9 and closer to 0.95 suggesting that inundation may occur more frequently than annually.

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This can also be considers as follows, by the end of the century (the year 2100) an asset situated at a level of approximately 1.9m AHD will have the same inundation likelihood (0.01 exceedance probability) as one currently situated lower than 1.2m AHD. The above values have not included additional contributions of wave set up and run-up which has been determined for this site. Additional contributions to inundation for this site have been identified to include riverine flooding contributing to elevated surface levels of Georges Bay.

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The township of St Helens used in this case study has a number of assets and areas

vulnerable to inundation and will be further impacted by future sea-level rise.

In addition to sea-level rise, other inundation components such as wave setup and runup

plus riverine flood contributions into the estuary and Georges Bay further increase the

vulnerability.

Changes in climate under the high greenhouse gas emission scenario are projected to

significantly impact both the intensity of rainfall events and the effects of run-off which

will further contribute to inundation hazards by the end of the century.

The following slides presents examples of potential inundation projected for an event

with a 0.01 exceedance probability (including potential contributing effects of wave

setup and runup and also river flood contributions) for one of the vulnerable sites.

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This slide represents the situation now (without future sea-level rise factored in) The above schematic illustration highlights a number of coastal locations where road access and other assets are identified as CURRENTLY vulnerable to sea levels exceeding the normal tidal cycle. The yellow to red scale colouring indicates locations which may be inundated due to events more frequent than an annual exceedance probability of 0.01 or 1% likelihood.

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This represents the situation in 2100. This model indicates that when sea-level rise is considered, the vulnerable assets are likely to become so under normal daily tidal cycle conditions.

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