Client: Hobart Airport Tasmania

Project Summary:

The project focused on the drainage of and through the Hobart International Airport. External catchments were particularly important due the location of the runaway to Tiger Head Bay discharge outlet.

The investigation was prompted by the design work associated with the upgrades of the Airport in line with the Hobart Airport Master Plan (2015). The plan outlines the airports direction for the next 20 years, though particular focus is on the 2015-2020 period with two major capital works projects. As described (HAMP, 2015):

• The construction of a 500m runway extension to enable direct flights from Tasmania to South-East Asia for passenger and freight opportunities.
• Changes to the layout and size of the passenger terminal, which will offer an improved experience for airport visitors.

Project Recommendation:

Several options were proposed to the client to reduce flood risk from the large upstream catchment to the apron extension: 

• Do nothing – the effects are shown to occur somewhere between a 10% annual possibility and a 1% possibility. This may be an acceptable risk, though it should be noted that this is below general community and engineering standards.
• Upgrade the crossings under or through the runway. Preliminary estimates from this modelling show that the upgrades would have to be at least double the existing 3 x 975mm pipes to reduce the worst of the flooding.
• Look to offsite choking of flows, and better utilisation of the existing upstream basin. 
• Land ownership details are unknown, but careful consideration of the offsite impacts will need to be undertaken.

Key Features and Innovations:

• Large scale modelling of external catchments and its interaction to a growing airport.