Storm surge and flood prone land
The placement of Hobart in the relatively short distance between Mount Wellington and the Derwent Estuary means that there a large number of watercourses running through the city. The steep slopes of Mount Wellington and the high rainfall nature of Tasmania means that there can be a considerable amount of water moving very quickly down Hobart’s watercourses. The urban layout of Hobart has resulted in many residences being built close to watercourses and the coast where they could potentially be impacted by flooding or storm surge.
We have modelled storm surge and flood prone areas in Hobart, including some sections of the Hobart Rivulet, New Town Rivulet and Sandy Bay Rivulet, to determine the level of risk of flooding during a storm surge. This information shows us what is likely to happen in a storm event.
The land that is considered at risk of storm surge is all land below 3 metres on the Australian Height Datum (Tasmania AHD83), where 0 is Tasmania’s approximate sea level in 1972.
If you are considering developing on land close to any watercourse it is important to understand what may happen in the future.
View the Storm Surge and Flood Prone Areas maps.
The indicative plans show the approximate 3 metre datum and land for those sections of Hobart’s urban watercourse prone to flooding at the 1% annual exceedance probability (AEP) level of risk. The maps provided show an indicate level of water based on modelling. Should you be considering developing in the flood or storm surge prone areas further modelling may be required to determine the actual risk to the property.
The maximum 1% Annual Exceedance Probability (AEP) for the year 2100 is 1.943 metres above AHD83 in the Hobart Region. A 1 metre freeboard is then added to account for wind and ocean swell generated waves. This totals 2.934 metres, rounded up to 3 metres.
Please note: AEP means the likelihood of a flood of a particular size (or larger) in any one year, usually expressed as a percentage. For example, if a peak flood discharge of 100 cubic metres per second has an AEP of 1%, there is a 1% chance (approximately equivalent to an average recurrence interval of 100 years) of a peak flood discharge of 100 cubic metres per second or larger occurring in any one year. However, the AEP of a flood event gives no indication when a flood of that size will occur next.
City of Hobart Flood Studies
The City of Hobart has commissioned a number of flood studies on the main watercourses in Hobart. The purpose of the flood studies are to provide a more detailed flood assessment of each catchment for more accurate flood level prediction.
- Hobart Rivulet Flood Study 2013
- Sandy Bay Rivulet Flood Study 2014
- New Town Rivulet Flood Study (pending completion)
For more information about construction in flood prone areas or current flood studies, please telephone 03 6238 2886 or email firstname.lastname@example.org.