Sandy Bay Rivulet – flood study
Client: Hobart City Council
Location: Tasmania, Australia
Date: April 2012 – December 2012
Reviewing and updating flood studies and inundation maps to account for the possible impacts of climate change and better manage risk
Background
Sandy Bay Rivulet drains into the Derwent River through two suburbs south of Hobart. The rivulet is approximately 7 km long with a catchment area of 6.5 km2. It has two 19 m high earthfill dams approximately 4.05 km and 4.5 km upstream of the mouth of the rivulet.
The Hobart City Council engaged Entura to review and update the flood studies of Sandy Bay Rivulet completed in 1999 and 2002 to include the impacts of climate change on predicted rainfall intensities and sea level rise. The hydraulic model was required to be converted from a 1D model to an integrated 1D/2D model.
Solution
For this study:
- an existing hydrological model was reviewed and updated with minor modifications
- inflow hydrographs were produced for six flood annual excedence probabilities (AEP) up to the 1:500 AEP with and without the impact of climate change on increased rainfall intensities
- the existing (1999) 1D MIKE 11 hydraulic model was used as the basis for modelling with the original cross sections being replaced with cross sections extracted from a 2008 lidar survey
- the updated MIKE 11 model was integrated into a 1D/2D MIKE Flood model (2 m grid) covering the approximate lower half of the model which is the most heavily populated area along the rivulet
- the MIKE Flood model was run for the 12 flood scenarios
- flood inundation maps were prepared for seven of the flood scenarios.
Outcome
Entura’s expertise in hydrology, climate change impacts, hydraulic modelling and GIS floodplain mapping were critical to providing the client with reliable, up-to-date information to improve risk management and decision making into the future, improving public safety, protection of infrastructure, and reducing financial impacts of flooding.
