Gascoyne River Flood Reinstatement Works

Road Infrastructure Damage

 

Background

A monsoonal low across the North West coast resulted in record rainfall and extensive flooding in the Gascoyne region and adjacent areas in December 2010.  The Gascoyne River peaked at 7.79 metres on the morning of 20 December, a record for the river with flood waters receding very slowly over several days.  River levels at The Wooramel River (120 km to the south of Carnarvon) and Yandoo Creek (40 km to the north) also reached the banks flood levels with many other smaller creeks and floodways experiencing major flows.

Floodwaters caused widespread damage to homes, plantation crops, pastoral leases and livestock, as well as local and state road infrastructure.

North West Coastal Highway (NWCH) received extensive damage over a 220km section extending from approximately 150 km to the south and 70 km to the north of Carnarvon, including:

  • Two major washouts within 20 km south of Carnarvon – 375 m and 110 m long sections;
  • 5 km of bitumen seal washed away;
  • 123 km of scoured road shoulders and sealed edges (up to 2 m deep in some places);
  • 5 km of earthwork embankments badly eroded; and
  • damage to various off-road drains.

NWCH was closed for eight days north of Carnarvon, and 13 days south of Carnarvon, with initial reopening's kept to daylight hours only, in order to ensure a safer journey for road users.  Main Roads had major concerns that closures would impact many businesses in and around the Gascoyne region and worked tirelessly over the festive season to expedite the reopening of the highway.

View Map of State Road Damage.

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Scope

Temporary repairs to enable NWCH to be re-opened were completed shortly after the flood event allowing traffic to travel the complete highway just days before the new year.

An Alliance contract was awarded to undertake permanent reinstatement works which commenced in May 2011.  The majority of the works package was completed by October 2011 with some outstanding sealing works were delivered in mid-2012.

Reinstatement costs are in the order of $8m. The proclamation of this flood event as an “eligible disaster” under the Western Australia Natural Disaster Relief and Recovery Arrangements (WANDRRA) will enable a large percentage of the road repair and restoration costs to be claimed from the Commonwealth via the Australian Governments Natural Disaster Relief and Recovery Arrangements (NDRRA).

Carnarvon’s Flood Mitigation Plan has been reviewed to incorporate the data from the December 2010 flood event. Please visit Carnarvon Flood Mitigation Works page for further information.

 

Local road damage

Main Roads undertook repair and reinstatement works on the damaged Carnarvon - Mullewa Road between Carnarvon and the Gascoyne Junction on behalf of the Shires of Carnarvon and Upper Gascoyne.  Both Shire CEO’s endorsed this work to be done as part of our current arrangements to complete construction and sealing of the final unsealed section to Gascoyne Junction.

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Modified: 03 Sep 2014