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Floodplain Mapping in Tasmania

The Floodplain Mapping Process

Joint Federal, State and Local Government funding arrangements have allowed the development of floodplain maps in many flood prone urban areas of Tasmania.

A significant feature of the floodplain mapping process has been the level of co-operation required between all tiers of Government and across Agency boundaries. The development of floodplain maps covering a large percentage of Tasmania's flood prone areas in this short period of time is testimony to the co-operation of all involved.

Under the mapping program a set of floodplain maps were produced during the 1990s, covering eight urban areas - Huonville, New Norfolk, the lower Jordan River, Richmond, Longford, Perth, Latrobe and Deloraine. Projects were funded under the former Federal Water Resources Assistance Program and the National Landcare Program, and more recently under the Natural Heritage Trust.

In addition to the inundation maps, comprehensive documentation has been prepared for each flood study. These reports provide a means of preserving technical results and model details for the review of flood inundation in the future. Copies of the reports are held by the relevant Council and may also be viewed at libraries of the Department of Primary Industries, Water and Environment.

Flood studies and risk assessments may be eligible for funding under the Natural Disaster Resilience Grants Program (NDRGP).

Extreme Events

Floodplain maps provide the best available estimates of the areas inundated with 1:20, 1:50 and 1:100 annual exceedance probabilities. That is, those areas which might be expected to be inundated with a 1 in 20, 1 in 50 or 1 in 100 chance in any given year.

The detailed information collected as part of these studies does allow extrapolation to more extreme flood events. However, it was considered that such estimates did not warrant the cost of the work involved during the current round of projects. More extreme events should be considered in situations where emergency facilities such as hospitals are to be sited near rivers, where the level of damage is very high indeed, and in cases of significant potential for loss of life. Provided there is an adequate information collection system established for future floods, estimates of the effects of extreme events may be possible when floodplain maps are revised.

While the current maps are based upon the best available data, new flood events and longer periods of record may lead to significant revisions to the estimates. To ensure the continuing applicability of the maps prepared under this program it is necessary to revise the estimates of flood probabilities every 15 to 20 years as well as after major flood events.

Many of the studies have been constrained by inadequate hydraulic information. There is a clear need to ensure that the hydraulics of all significant floods are monitored in future and this is best completed by establishing cross-sections, across which velocity and depth measurements can be taken, together with documentation and photographs of floods.

Flood Data Books are a collation of information about Tasmanian floods.

Available Maps

Please note: these are large image files which may take some time to download. To obtain higher resolution and more control of the map, it is recommended that you download the file to your PC, then open it with a graphics application.

Contact

Water Enquiries
GPO Box 44
Hobart TAS 7001
Phone: 1300 368 550
Email: Water.Enquiries@nre.tas.gov.au