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Rockhampton can build a safe flood levee - project manager

How the flood Fitzroy River flows with the levee bank
How the flood Fitzroy River flows with the levee bank

JIM Niehoff noticed something remarkable about Rockhampton when he came here to lead the $1.2 million flood levee project study.

He had found a city brimming with authorities on levees.

The project manager for AECOM's Rockhampton levee project team shared that observation as he spoke at a 40 person public briefing last week.

"It's obvious from reading the newspaper and listening to the radio that the people of Rockhampton have become experts on levees," he said to chuckles from the invitation-only audience.

"In many respects this is very good. They're looking into educating themselves about what a levee is and the potential for what can go wrong with it.

"(But) I have seen quite a few more levees I think than most of the folks in Rockhampton."

He was introduced as an international expert on levees and proceeded to demonstrate that.

One of his most recent jobs was a $1 billion flood mitigation project in Saudi Arabia following two devastating floods in 2009 and 2011 that killed more than 160 people and caused massive damage to property.

His home town is Denver Colorado where there is a levee to protect the city from frequent flooding despite a very dry climate

He pointed out almost every major city in the United States is built on a major river system and most have levee systems.

Geotechnical Practice Leader at AECOM

James Niehoff

International geotechnical engineering consultant with more than 35 years' experience with the design and construction of foundations for low to high-rise buildings, levees, earth and rockfill dams, landfills, mining and tailings ponds, deep excavations and seismic evaluation.

He has no doubt a safe levee can be built in Rockhampton.

"My wife thinks I'm a very negative person," he said as he sought to answer community concerns about the possibility the levee could wreak havoc by overflowing or breaking.

"That comes from being an engineer as I am constantly trying to decide how something can fail so you can design some aspect that will prevent that failure.

"We read in the paper just about every day what can happen if this occurs and this happens, well that's what we think about every single day when we are putting together design aspects."

If the water level gets higher than the levee a spillway section (in Fiddes St) would allow it to flow over the top, preventing overtopping elsewhere so the water level rises slowly on the inside and outside so it balances out, equalising the pressure on both sides.

AECOM experts spoke about key levee engineering and planning facts.

Some Key Levee Facts:

  • The levee will keep out a 10.38 metre flood (includes 900mm freeboard) and will protect against a 1 in 100 year flood event which includes the highest flood recorded in Rocky being the 10.1m 1918 event.
  • There is additional height to take care of a wave run up, if the levee settles, plus other contingencies.
  • As it follows the land contours, the levee would range from under a metre to 4 metres in height with a predominant height of 1m to 2m.
  • Temporary levee system in Quay and Wharf Sts but the predominant construction will be slopping earthen embankments designed to prevent wave run-up.
  • During the flood event temporary walls will be built in.
  • In other locations a composite section where a temporary wall is placed on top where the levee is more than 1m in height.
  • In some limited short locations a crib retaining wall system.
  • There is a critical focus at the Yeppen crossing. Final models are still being checked.
  • Getting water through there in a smooth manner limits the impact on properties upstream.
  • The levee alignment at Yeppen includes a taper designed to allow water to smoothly flow around Hastings Deering to lessen the impact.
  • Internal drainage features include pump stations to remove excess water.
  • Levee is designed to control seepage.
  • Levees are becoming more widespread The Mackay levee has been integrated into parkland and has withstood two floods already.
  • May 10 open day 10am -2pm Littler-Cum-Ingham Park, Quay St.

Topics:  aecom flood levee rockhampton regional council



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