Imbil Town Bridge increases the turbulence in Yabba Creek during floods

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A Moderate Flood in Yabba Creek, at its peak of 7.7M, submerges Imbil Town Bridge, whilst the bridge structure and its pedestrian railings impede the flood and increase the turbulence thus increasing stream bank erosion downstream.

Flood Peak on 26 Feb 2013.

A month earlier the third highest flood in memory peaked here at 10.7M. During a flood of that magnitude, the water flow in Stehbens Reach and Town Reach exceeds 80kph.

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Comments (6)

Nick Weall on February 26, 2013

It never rains but it pours ~ Poor old Oz is going through the weather wars it seems ~~~

Ian Stehbens on February 26, 2013

Hello Nick,

Seems is a reality, it seems!

The flood in the Burnett Catchment a month ago was a 1 in 500 year event, and that exceeds even insurance company risk assessment frameworks. Their greatest flood language has been 1 in 200 until now. As Oz has only a 220 year modern history it is a bit hard to predict what a 1 in 500 year event may look like.

North Bundaberg in particular, and all upstream towns saw devastation and extensive orchards, canelands and cattle properties have suffered great losses in that flood.

Moderate floods like the one pictured do damage to bridges and their approaches, roads, fences mostly. In most areas, land use adjustment to floods and emergency responses are excellent, but the variability and risk assessment will always mean loss and damage does occur.

But when higher than ever known floods occur, then there is widespread heartbreak and that's what we saw in Bundaberg a month ago.

In our valley, the Yabba/Mary, we experienced a super flood in 1893, so we know that level, but what I don't know is whether that was a 1 in 500 extreme event or a mere 1 in 200 year super event. The 1893 rainfall record is still a 24 hour record for Australia I think, so here's hoping it is never broken!

Ian

bdeh on February 27, 2013

That flood will damage the bridge again Ian. That costs a lot to repair and the tax payer will find the bill some day.

Oz has a problem with the weather conditions the last period. I read that there's a warning for a hurricane in WA (Broome to Port Hedland), that it's to dry in the region of Perth and the Eastern part is getting to much rain. Greetings Berend

Ian Stehbens on February 28, 2013

There was very little damage to the bridge this time, Berend, primarily because the major flood a month ago had removed the river bank trees and a 25000L tank that collided with the bridge in that flood, so this was a relatively clean flood. There has been more scouring around the bridge and river bank erosion downstream that is partly due to the turbulence created by the bridge.

Yes we are taking a hammering over the last three years with drought, bushfire, flood, cyclones all being very intense and many new records being set.

But we learn to adjust and pull together.

The Tropical cyclone crossed the coast east of Port Hedland yesterday afternoon. I am not up to date on what damage has been wreaked by that category 4 cyclone.

Ian

stilinovich on March 5, 2013

we've stayed just around the corner at imbil bridge farm a few times. do you know if they were spared? (they are up high thankfully)

Ian Stehbens on March 5, 2013

Imbil Bridge Farm is above major flood level, Stilinovich, but their stairway access to the river was probably damaged. The sad thing that I have noticed is that the high clay banks at the Big Hole (between Imbil Bridge Farm and Island Reach Camping Ground) have been severely eroded. I believe a major factor in this erosion has been the design of Imbil Town Bridge (built after the 1999 flood which was almost the same flood height as the Jan 27, 2013 flood, and 3M higher than the one pictured here) which creates significant lateral and vertical turbulence in the river in this section.

If you have stayed at the farm you may also have known that these banks on both sides of the river were the home of a colony of platypus. I hope they anticipated the flood and headed away from the river to safety somewhere in a quiet farm dam, or up Cherry Gully (that flows through Imbil Bridge Farm.

Thanks for your comment.

Ian

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  • Uploaded on February 26, 2013
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    by Ian Stehbens

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