Geomorphic impact of the January 2011 flood on Murphys Creek, southeast Queensland

Thompson, Chris J., Croke, Jacky C. and Pietsch, Tim (2012). Geomorphic impact of the January 2011 flood on Murphys Creek, southeast Queensland. In: 6th Australian Stream Management Conference: Managing for Extremes. Proceedings. 6ASM: 6th Australian Stream Management Conference, Canberra, ACT, Australia, (23-30). 6-8 February, 2012.

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Name Description MIMEType Size Downloads
Author Thompson, Chris J.
Croke, Jacky C.
Pietsch, Tim
Title of paper Geomorphic impact of the January 2011 flood on Murphys Creek, southeast Queensland
Conference name 6ASM: 6th Australian Stream Management Conference
Conference location Canberra, ACT, Australia
Conference dates 6-8 February, 2012
Proceedings title 6th Australian Stream Management Conference: Managing for Extremes. Proceedings
Place of Publication Canberra, ACT, Australia
Publisher River Basin Management Society
Publication Year 2012
Sub-type Fully published paper
Open Access Status
ISBN 9780734047625
Start page 23
End page 30
Total pages 8
Chapter number 4
Total chapters 206
Language eng
Formatted Abstract/Summary
Key Points
• Murphys Creek is a headwater catchment of the Lockyer Valley draining the eastern flanks of the main range
• Gauging station data from upper Murphys Creek indicate an event average return interval exceeding 1000 yr
• The magnitude and frequency changed dramatically from the top to the bottom of the Lockyer catchment
• The geomorphic setting of lower Murphys Creek exposed the channel to extreme values of stream power
• Scouring of channel banks and benches along the confined channel resulted in a 3-­fold increase in channel width and a net export of 476 188 t of sediment from the reach

Murphys Creek is one of the main headwaters of the Lockyer Catchment and was subject to the devastating January 2011 floods in southeast Queensland. Rainfall leading to the event had a moderate-­high return interval, however, the already wet catchment resulted in a very high rainfall-­runoff coefficient causing flash flooding. This paper uses gauging station data, pre-­ and post-­flood LiDAR data and modeling to evaluate the flood peak hydraulic characteristics and predict flood peak transport capacity. Major channel change occurred throughout the confined reach with benches being stripped and channel banks eroded. Channel width increased up to three times the pre-­flood width. Peak unit stream powers reached 4700 W m-2 at points along the confined channel but do not appear to be high enough to entrain the exposed boulders (>2 m in diameter) evident on the channel bed after the flood. The relatively high degree of channel change in this reach is due not only to the confined valley setting in which floodwaters remain concentrated, but also to the high energy gradient of the reach and the proximity to source of the rainfall in the headwaters of the catchment.
Keyword Lockyer Valley
Extreme flood
Channel change
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Other title: "The geomorphic impact of the January 2011 flood on Murphy's Creek, Southeast Queensland".

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Created: Fri, 05 Dec 2014, 12:09:07 EST by Helen Smith on behalf of School of Geography, Planning & Env Management