Has Lockyer Creek Changed Since European Settlement?

THE BIG FLOOD: WILL IT HAPPEN AGAIN? Has Lockyer Creek changed since European settlement?

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

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

Twelve different types of geomorphic adjustment have Change in geomorphic unit assemblage (D) been identified along Lockyer Accretion (D) and Creek. Floodplain sand Bank failure (E) sheets (D) These are categorised as erosional (E), depositional (D) and reorganisational (R).

Lockyer Creek can be described Inset channel Bank extension (E) Chute (E) realignment (D) as a resilient system as it has not experienced catastrophic geomorphic adjustment when Comparison of Helidon (Drover’s Crossing), 1890s and 2014 compared to other rivers historical and contemporary in eastern Australia. Fine- photographs grained sediments, terraces, from Lockyer bedrock, vegetation and a large Creek macrochannel have ‘held the shows little geomorphic system together’ in the period change. Gatton Railway Bridge, 1866 and 2014 since European settlement. (photos: However, the system may not be Queensland so resilient in the future and it is State Library and K. Fryirs) possible more adjustments will occur along the macrochannel. FURTHER READING

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 Has Lockyer Creek changed since European settlement?

Geomorphology 241 (2015) 55–71

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Geomorphology

journal homepage: www.elsevier.com/locate/geomorph

Morphological and historical resilience to catastrophic ﬂooding: The case of 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, Australia b Department of Geography, Planning and Environmental Management, University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia c Department of Science, Information Technology, Innovation, and the Arts (DSITIA), Queensland Government, Ecoscience Precinct, Dutton Park, Brisbane, Queensland 4102, Australia

article info abstract

Article history: This study aimed to determine the extent of geomorphic change resulting from the catastrophic flood of 2011 in Received 28 November 2014 the Lockyer Valley in southeast Queensland and to place these impacts within a history of geomorphic Received in revised form 7 April 2015 adjustment. Aerial photographs dated from 1933 to 2011 and parish maps and historical on-ground photographs Accepted 8 April 2015 dating from 1865 to 1966 were examined for evidence of geomorphic adjustment since European settlement in Available online 18 April 2015 the first half of the nineteenth century. Eleven forms of geomorphic adjustment were identified in three Keywords: categories; erosional, depositional, and reorganisational. Only 26% of the Lockyer Creek channel length has Catastrophic flood been affected by some form of geomorphic adjustment since European settlement. Most of this adjustment River sensitivity was localised and dominated by reorganisation of geomorphic unit assemblages within the macrochannel and Evolutionary trajectory sediment deposition on floodplains. No wholesale river change in the form of lateral migration or avulsion has River change occurred, and the river's morphology has remained relatively characteristic over time (i.e., morphology remains Antecedent control relatively uniform in a reach-averaged sense). Geomorphic responses to extreme flooding have been minor, and Lockyer Creek the geomorphic effectiveness of floods in this system (including the 2011 flood) has been limited over the last several hundred years. The system is likely still adjusting to past flooding events that ‘set’ the morphology of the current system (i.e., the macrochannel). A form of event resilience has resulted in this system such that it is less prone to geomorphic adjustment during events than would normally be considered geomorphically effective. 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 the resilience of this system will hold in the future, with more extreme episodes of flooding predicted to occur in this region under future climate change. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Perhaps inevitably, studies of river change tend to emphasise reaches that have experienced dramatic adjustments (i.e., metamorphosis; Flooding is a natural and vital process in any fluvial environment. Schumm, 1969). Many studies have focused on instances of wholesale However, the sensitivity or resilience of a river system to geomorphic changes in river type, demonstrating how multiple autogenic and allo- adjustment varies significantly depending on landscape structure and genic factors and conditions can interact to produce complex landscape condition (i.e., preconditioning of the system) and on the role of responses along rivers (Magilligan, 1992; Magilligan et al., 1998, 2015; disturbing and resisting forces on the system at the time of the event Phillips, 2010; D'Arcy and Whittaker, 2014). A body of literature has (Wolman and Miller, 1960; Wolman and Gerson, 1978; Beven, 1981; focussed on river sensitivity to human-disturbance, particularly in the Costa and O'Connor, 1995). Brunsden and Thornes (1979), Brunsden post-Industrial Revolution and post-colonial periods (Brierley et al., (2001), and Thomas (2001) defined disturbing forces as the application 2005; Gregory, 2006). More recently, catastrophic flooding in many of energy from a specific tectonic, climatic, or anthropogenic distur- parts of the world (particularly in the 2010s) has seen a plethora of bance and resisting forces as the ability of the system to resist displace- activity in analysis of river adjustments to floods of high magnitude ment from an initial state or condition. Landscape change is considered and low frequency (Dean and Schmidt, 2011, 2013; Croke et al., Forto more take place information as a normal process about–response the project function to these distur- 2013a; Thompson and Croke, 2013; Buraas et al., 2014; Magilligan bances and may involve structural rearrangement of the system if the et al., 2015). What is obvious is that geomorphic responses to cata- Website:forces appliedwww.thebigflood.com.au are greater than system resistance (Brunsden, 2001). strophic floods vary in different settings, catchments, rivers, and reaches and that the sensitivity of systems to these events has been Email:⁎ Corresponding [email protected] author. highly varied. Not all rivers have shown the same form, rate and extent E-mail address: [email protected] (K. Fryirs). of adjustment in response to human disturbance or catastrophic