On the morning of 4 March 2012, freight train 7SP3 operated by Pacific National derailed after entering floodwaters that had overtopped the track near Roto in New South Wales.
The flooding had caused scouring of the track formation, compromising its capacity to support the train.
The lead locomotive remained on the track but the trailing locomotive derailed and uncoupled. None of the trailing wagons derailed although a number sustained damage. The flooding and subsequent derailment of the second locomotive of train 7SP3 damaged approximately 130 m of track. The crew were shaken, but physically unhurt.
What the ATSB found
The ATSB determined that runoff from the heavy rain that had fallen in the catchment area adjacent to Roto the morning of 4 March 2012 caused a flash flood event. The volume of floodwater exceeded the capacity of a drainage culvert, which resulted in water overtopping the track formation with ballast and sub-grade scouring on either side of the culvert.
The magnitude of the scouring meant that the track could not support the weight of train 7SP3 as it passed over the affected areas. The resulting deformation in the alignment of the track initiated the derailment.
The ATSB also found that the track manager’s systems and operational procedures provided limited information and guidance to assist the network control staff in identifying and assessing the potential threat to the safety of rail traffic resulting from the significant localised weather event.
What's been done as a result
The track manager is trialling the use of flood sensors at high-risk locations and has engaged the services of a third party to provide early warning information on potential high-risk weather events.
It is essential that rail transport operators have robust systems in place to monitor and mitigate the risks to infrastructure from significant weather events to ensure that the safety of rail operations is not compromised.