FURTHER READING

THE BIG FLOOD:WILL IT HAPPEN AGAIN?

Fryirs, K., Lisenby, P. and Croke, J. 2015. Morphological resilience to catastrophic flooding: the case of Lockyer Creek, SE Queensland, Australia. Geomorphology. 241, 55-71. doi:10.1016/j.geomorph.2015.04.008

Along Lockyer Creek, 26% of the channel has experienced some change or adjustment since the time of the first parish maps in 1886.

Has Lockyer Creek changed since European settlement?

Adjustments are local and dominated by changes to macrochannel width and the type of geomorphic unit (landforms) within the macrochannel. The most significant changes in the Lockyer have occurred upstream of Gatton and mainly after 1974 and in 2011.

Twelve different types of geomorphic adjustment have been identified along Lockyer Creek.

These are categorised as erosional (E), depositional (D) and reorganisational (R).

Lockyer Creek can be described as a resilient system as it has not experienced catastrophic geomorphic adjustment when compared to other rivers in eastern Australia. Fine-grained sediments, terraces, bedrock, vegetation and a large macrochannel have ‘held the system together’ in the period since European settlement. However, the system may not be so resilient in the future and it is possible more adjustments will occur along the macrochannel.

Comparison of historical and contemporary photographs from Lockyer Creek shows little geomorphic change. (photos: Queensland State Library and K. Fryirs)

Helidon (Drover’s Crossing), 1890s and 2014

Gatton Railway Bridge, 1866 and 2014

Removal (E)

Widening (E)

Bank failure (E)

Bank extension (E)

Scour (E)

Formation (D)

Accretion (D) and Floodplain sand

sheets (D)

Chute (E)

Incision (E)

Change in geomorphic unit assemblage (D)

Inset channel realignment (D)

For more information about the projectWebsite: www.thebigflood.com.au

Email: info@thebigflood.com.au

Has Lockyer Creek changed since European settlement?

Morphological and historical resilience to catastrophic flooding: The caseof Lockyer Creek, SE Queensland, Australia

Kirstie Fryirs a,⁎, Peyton Lisenby a, Jacky Croke b,c

a Department of Environmental Sciences, Macquarie University, North Ryde, NSW 2109, Australiab Department of Geography, Planning and Environmental Management, University of Queensland, St Lucia, Brisbane, Queensland 4072, Australiac Department of Science, Information Technology, Innovation, and the Arts (DSITIA), Queensland Government, Ecoscience Precinct, Dutton Park, Brisbane, Queensland 4102, Australia

a b s t r a c ta r t i c l e i n f o

Article history:Received 28 November 2014Received in revised form 7 April 2015Accepted 8 April 2015Available online 18 April 2015

Keywords:Catastrophic floodRiver sensitivityEvolutionary trajectoryRiver changeAntecedent controlLockyer Creek

This study aimed to determine the extent of geomorphic change resulting from the catastrophic flood of 2011 inthe Lockyer Valley in southeast Queensland and to place these impacts within a history of geomorphicadjustment. Aerial photographs dated from 1933 to 2011 and parishmaps and historical on-ground photographsdating from 1865 to 1966 were examined for evidence of geomorphic adjustment since European settlement inthe first half of the nineteenth century. Eleven forms of geomorphic adjustment were identified in threecategories; erosional, depositional, and reorganisational. Only 26% of the Lockyer Creek channel length hasbeen affected by some form of geomorphic adjustment since European settlement. Most of this adjustmentwas localised and dominated by reorganisation of geomorphic unit assemblages within the macrochannel andsediment deposition on floodplains. No wholesale river change in the form of lateral migration or avulsion hasoccurred, and the river's morphology has remained relatively characteristic over time (i.e., morphology remainsrelatively uniform in a reach-averaged sense). Geomorphic responses to extreme flooding have beenminor, andthe geomorphic effectiveness of floods in this system (including the 2011 flood) has been limited over the lastseveral hundred years. The system is likely still adjusting to past flooding events that ‘set’ the morphology ofthe current system (i.e., the macrochannel). A form of event resilience has resulted in this system such that itis less prone to geomorphic adjustment during events than would normally be considered geomorphicallyeffective. As a result, antecedent controls on macrochannel presence and capacity are considered to be first-order controls on contemporary forms and processes in this system. Work is required to test whether theresilience of this system will hold in the future, with more extreme episodes of flooding predicted to occur inthis region under future climate change.

© 2015 Elsevier B.V. All rights reserved.

1. Introduction

Flooding is a natural and vital process in any fluvial environment.However, the sensitivity or resilience of a river system to geomorphicadjustment varies significantly depending on landscape structure andcondition (i.e., preconditioning of the system) and on the role ofdisturbing and resisting forces on the system at the time of the event(Wolman and Miller, 1960; Wolman and Gerson, 1978; Beven, 1981;Costa and O'Connor, 1995). Brunsden and Thornes (1979), Brunsden(2001), and Thomas (2001) defined disturbing forces as the applicationof energy from a specific tectonic, climatic, or anthropogenic distur-bance and resisting forces as the ability of the system to resist displace-ment from an initial state or condition. Landscape change is consideredto take place as a normal process–response function to these distur-bances and may involve structural rearrangement of the system if theforces applied are greater than system resistance (Brunsden, 2001).

Perhaps inevitably, studies of river change tend to emphasise reachesthat have experienced dramatic adjustments (i.e., metamorphosis;Schumm, 1969). Many studies have focused on instances of wholesalechanges in river type, demonstrating how multiple autogenic and allo-genic factors and conditions can interact to produce complex landscaperesponses along rivers (Magilligan, 1992; Magilligan et al., 1998, 2015;Phillips, 2010; D'Arcy and Whittaker, 2014). A body of literature hasfocussed on river sensitivity to human-disturbance, particularly in thepost-Industrial Revolution and post-colonial periods (Brierley et al.,2005; Gregory, 2006). More recently, catastrophic flooding in manyparts of the world (particularly in the 2010s) has seen a plethora ofactivity in analysis of river adjustments to floods of high magnitudeand low frequency (Dean and Schmidt, 2011, 2013; Croke et al.,2013a; Thompson and Croke, 2013; Buraas et al., 2014; Magilliganet al., 2015). What is obvious is that geomorphic responses to cata-strophic floods vary in different settings, catchments, rivers, andreaches and that the sensitivity of systems to these events has beenhighly varied. Not all rivers have shown the same form, rate and extentof adjustment in response to human disturbance or catastrophic

Geomorphology 241 (2015) 55–71

⁎ Corresponding author.E-mail address: kirstie.fryirs@mq.edu.au (K. Fryirs).

http://dx.doi.org/10.1016/j.geomorph.2015.04.0080169-555X/© 2015 Elsevier B.V. All rights reserved.

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