Why is award-winning bridge flood-prone?

02:18, Mar 11 2014
Fitzgerald Ave under flood
UNDER WATER: The Avon River poured across the new section of Fitzgerald Ave in last week's flood.

Designs for Fitzgerald Ave earthquake damage repairs did not include flood modelling and possibly increased the flood risk, the Christchurch City Council has confirmed.

Press columnist Mike Yardley today described the multimillion-dollar project, which took more than a year to complete, as an ''epic fail'' after it became swamped for the second time in heavy rainfall last week.

''Partially closed by flooding last June and fully submerged as the Fitzgerald reef last week, why was it constructed at such a ridiculously low level?'' he questioned.

The Opus-designed, Downer-built project last year won a national infrastructure excellence award.

Council transport and greenspace unit manager John Mackie today said the repair was city's earliest earthquake rebuild roading projects when work began in April 2011 and urgency was needed.

''At this time, no flood modelling had been done and the focus was on urgently opening this important arterial road to traffic, while also significantly increasing its ability to withstand lateral spread in any future earthquake event,'' he said.


''This was a time of uncertainty; there were ongoing earthquakes and ground levels were continuing to change. Decisions around land zoning had not been made for the area of houses to the east of the road.''

On the western side between the road and the river, the original wall had a solid, concrete safety barrier on top.

The design for the new wall instead used an open metal crash barrier on top to improve visibility of pedestrians and cyclists on the path below the road.

''Unfortunately, the open barrier allows water through and did not give the same flooding protection to the road as the previous barrier,'' Mackie said.

The council was working with Stronger Christchurch Infrastructure Repair Team to identify the best way to reinstate the additional flood protection previously provided by the solid concrete crash barrier, he said.

Yardley told The Press the lack of flood modelling ''beggars belief''.

''It's all very well to consider retrofitting the bridge with a reinstated flood-protecting concrete barrier, but the question still remains why the roadway is such a knuckle-dragger, dipping deep in places as low as the river itself?'' he said.



The Press