The township of St Helens on Tasmania’s North East Coast is particularly vulnerable to the effects of sea level rise in combination with other climate change impacts. An innovative project completed by Tasmanian engineering consultancy, pitt&sherry, in conjunction with the Water Research Laboratory (WRL) of UNSW and SGS Economics and Planning has assessed potential impacts of climate change on assets within the George River floodplain, adjacent to the St Helens township.
Within significant budget constraints, the project delivered a river flood analysis through assessment of historic rainfall, river flow and flood records integrated with the potential effects of extreme storm surge, projected sea level rises and modeled projected changes to rainfall. The project focused assessment on the 2004 river flood, an estimated 50 yr ARI event produced from an approximately 100yr ARI rainfall event and then incorporated variations based on potential future climate change impacts. Analysis indicated negligible storm surge contribution during the event with sea levels within normal diurnal tidal ranges.
Modeling of coastal processes applicable to the area undertaken by WRL provided indications of extreme storm tide levels for current and potential future annual, 10yr ARI and 100yr ARI scenarios. Climate Futures for Tasmania, high resolution climate modeling, completed by the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) provided projected rainfall changes for the catchment.
Floodplain analysis innovatively incorporated hydrologic modeling with anecdotal records to develop an appropriate flood surface model. Integration within Eonfusion, a cutting edge temporal and spatial analysis tool, combined the sea level rise and flood plain surface modeling to identify assets within the project area susceptible to the impacts of projected changes in climate.
The susceptible assets identified were then assessed to further determine vulnerability levels and consequences of inundation to determine a risk priority for treatment or future assessment.