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Big Flood Newsletter Issue 3, Nov 2014
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Issue 3: November, 2014

Welcome to the third issue of the ‘Big Flood’ Newsletter.  Following on from the Industry workshop in August, everyone has been busy in the last two months gathering and interpreting data. The students are all doing a great job at their respective components and many are starting to reveal very exciting results and drafting publications. We have also been involved more generally in two upcoming events which may also be of interest; the 16th Biennial Australia New Zealand Geomorphology Group (ANZGG) is holding its conference in Mt Tamborine between Nov 30th and Dec 3rd. All of the students are attending and presenting at this meeting and it will be a great opportunity for all of us to get some feedback on the work from those attending. In addition, we are hosting a Geomorphic Change Detection (GCD) workshop run by A/Prof Joe Wheaton from Utah State on Dec 4th and 5th at the University of Queensland. Industry Partners have been offered several places at this workshop and it’s a great opportunity to learn new skills and share ideas in the use of detecting geomorphic change using LiDAR. Both of these events will certainly promote the ARC project and its results so far and provide a great opportunity for us to share skills and engage with the national and international community on aspects relating to flood risk, geomorphology and catchment rehabilitation.  For further information on both events please contact Ramona Dalla Pozza. There have been quite a few papers submitted recently too and you can keep up-to-date on our publication list at the bottom of this newsletter.  

Stage 1 – To avulse or not to avulse?

 
Lead CI - Jacky Croke
PhD Students - James Daley and Daryl Lam

Thanks to the hard work of Ashneel Sharma (DSITIA), previously collected OSL samples from the Lockyer have now been completed and we are currently busy preparing the first batch of publications from this work. In addition, James Daley has submitted his batch of OSL samples for dating the terraces and floodplains around Helidon to determine the timing of extreme flood events estimated to exceed the Probable Maximum Flood (PMF) in some locations (see his report below). Last year Chris Thompson and I, together with the DSITIA soils group in the form of Don Malcolm, Jeremy Manders and Ian Hall, pushed the drill rig to its limits and extracted nearly 300 m of deep cores from the lower Lockyer (Figure 1). The aim was to extract material at the base of previously identified older channels which show some evidence for past episodes of channel relocation or avulsion. Avulsion is the process by which a channel relocates to an alternative location in often a rapid and unpredictable way. There are many aspects of the current Lockyer geomorphology that would suggest this system has the tendency to avulse. Although recent work by Stage 3 indicates that the Lockyer has not moved across the valley floor since European settlement, other work on thresholds for avulsion would suggest that the system is likely to experience this form of channel adjustment again in the future. Dating of the channel sands at the base, and in the middle, of several cores taken across the valley floor will allow us to predict the frequency of such stages of avulsion. Drilling also confirmed the presence of very thick units of fine-grained clays indicating that this part of the lower Lockyer floodplain was once dominated by low-energy, backwater, lake or channel infilling depositional processes. We are currently starting to analyse these clays with a view to reconstructing the vegetation characteristics and depositional environment for the Lockyer at this time. Thanks to Ashneel we hope to have a suite of dates on this by March next year. 

Stage 2 – Establishing a relationship between flood chronologies and climate variability.

 
Lead CI - Jon Olley
PhD Students  - Heather Haines and Jack Coates- Marnane

Work on Stage 2 is moving forward on several fronts.  Both the marine sediment analysis and the dendrochronology components as parts of Jack and Heather’s PhD projects have made progress and are described in more detail below.  The regional rainfall analysis demonstrating multiple patterns of rainfall across Southeast Queensland (SEQ) is being further developed to include a number of shorter duration instrumental records.  We hope that this will allow for a better understanding of the rainfall patterns across the region and allow for definite boundaries of what portion of SEQ each pattern represents.  We also hope to determine some of the factors causing these variations in regional rainfall through further study.  The Lockyer region appears to be represented by one regional rainfall pattern that demonstrates lower rainfall in the first half of the 20th century with higher rainfall levels in the later part of the 20th century (Figure 2).  More recently the amount of rain falling in the Lockyer valley appears to be closer to the 20th century average.
 
Additionally, results from ITRAX-XRF core scanning have recently been provided through an ANSTO grant awarded to members of the Stage 2 team and lead by Dr Justine Kemp (GU).  Three cores were analysed in this round of study; two from Madge’s Lagoon, an infilling meander cut-off in the Lower Lockyer, and one from Morton Bay (Figure 3).  Madge’s Lagoon is believed to represent an area of episodic flood deposition so by analysing the properties of the sediments at this location we hope to establish a flood chronology for the Lower Lockyer region.  Preliminary OSL dating suggests the top 2.5 m of this core represents sediments accumulated over the past ~ 3000 years.  The results from the XRF analysis suggest increasing particle size towards the surface.  We are now working on verifying these results using conventional particle size and geochemical analysis.  
Figure 2: Regional rainfall anomalies in the Lockyer Valley region over the 20th Century.
Figure 3: Map of the Lower Brisbane River sites showing coring locations.

 

Stage 3 – Geomorphic Assessment of River Response to Floods and Droughts.

 
Lead CI - Kirstie Fryirs
PhD candidate – Peyton Lisenby (MQ)
 
Stage 3 is currently focusing on two areas of research.  First, we are writing up findings from the historical analysis of river adjustment and change since European settlement.  To date, we have concentrated our work on the Lockyer trunk stream extending from Murphy’s Creek to the Brisbane River confluence. A range of parish maps, historical air photograph sets and archival on-ground photographs have been analysed. We have identified 10 different forms of channel adjustment in three categories (erosional, depositional and reorganisational).  We have found a patchy distribution of river adjustment with only around 20% of trunk stream length being affected since European settlement. Overall, this river has not shown significant signs of adjustment (unlike many other well-documented river systems in Eastern Australia). This paper will be submitted to the journal Geomorphology in coming months (Fryirs et al. in prep.). This work will be extended to the tributary systems as part of Peyton Lisenby’s PhD.
 
Second, stage 3 has used a DEM of Difference (DoD) to analyse patterns of erosion and deposition in the Lockyer valley resulting from the 2011 flood. The main findings are that 2,269,069 m3 of sediment was eroded along the main-stem and 2,991,310 m3 was deposited, making the catchment net depositional for this flood event. Deposition occurred on floodplains of expansion reaches (where flows went overbank) and volumes stored in these areas increased as you move downstream. Diminishing sediment transfer efficiency and longitudinal (dis)connectivity of sediment supply occurred in the catchment during this flood. This suggests that extreme floods in this system are inefficient at transferring sediment downstream, whereas small-moderate flows that are contained within the macrochannel are most efficient.  In terms of river management responses these findings suggest that to reduce end-of-catchment yields levee construction that concentrates flows to the macrochannel should cease, in-macrochannel vegetation roughness should be allowed to increase, and floodplains reactivated/inundated where possible so they act as long term sediment stores. This work has been submitted to the journal River Research and Applications (Thompson et al.).

Stage 4 – Modeling hydrological variability for geomorphic flood risk.

 
Lead CI - Chris Thompson

Stage 4 work over the past few months has focused on completing and applying a methodology for catchment scale specific stream power modelling. Work will continue with the Stage 1 and 3 research publication on sediment connectivity during floods and bank erosion processes. Research was presented at the 7th Australian Stream Management conference in Townsville.

A methodology for modelling the specific stream power of an Average Recurrence Interval (ARI) event has been developed and applied to the Burnett catchment (Figure 4). The model averages gauging station derived discharge, channel slope from SRTM-DEM and floodplain width over a 1 km scale to derive approximate flood peak power. The model can be used to identify locations of potential high risk to flood hazard where specific stream power is relatively high and also where abruptly changes from narrow confined reaches to wide floodplain reaches. A methods document outlining steps involved has been completed to enable the application of the model to other SEQ catchments.  
Figure 4:  Specific stream power model for Burnett catchment.
 
Research on sediment connectivity along the main channel and between the channel  and floodplain has been reported above in Stage 3.
 
Research has continued on the channel bank mass failures (BMF) following the 2013 flood. Preliminary analysis has shown that a similar pattern of BMFs occurred as in the 2011 flood, however the majority of 2013 BMFs occurred below Gatton. As shown previously, most (70%) 2013 BMFs occurred in original channel bank with no prior evident of mass failure. BMFs remained within the channel belt. Based on the accumulating number of BMF from prior and recent floods, only 30% of the channel bank length between Gatton and Lockrose has not failed (Figure 5). These results are being incorporated into a research paper questioning channel adjustment in subtropical catchments. 
Figure 5: Lockyer Creek distribution of Bank Mass Failures (BMFs).

PhD Updates 

James Daley -  Macrochannels


Recent catastrophic flooding throughout Queensland suggests that many streams are well adjusted to accommodate such floods, forming prominent macrochannels that expedite flood waters downstream. Considering their significance to flood conveyance, understanding how, when and why these macrochannels evolved is the primary objective of my thesis. Macrochannels are a common landscape feature throughout Queensland, though previous research suggests their occurrence is not related to catchment area or discharge. I am currently working on the spatial extent and delineation throughout the South East Queensland and Wide Bay Burnett region, where previous work has identified a peak in flood variability along eastern Australia. Building on modelling completed for the Burnett Catchment, macrochannel identification and stream power mapping is being undertaken through a GIS terrain analysis. This work will also focus on defining geomorphic parameters of macrochannels.To try and understand how and when these landscape features formed, approximately 40 samples are being analysed for OSL. These samples have been collected from the mid-reaches of Lockyer Creek between Lockyer Sidings and Grantham, previously recognised as an important transition zone in the stream network. Due to be completed in November 2014, the dates of these samples will be important in revealing the timing of macrochannel formation, terrace inundation and depositional processes on in-channel units.

A recent expedition from Lockyer Sidings to Helidon was undertaken to locate bedrock exposures along the beds and banks of the river, revealing exposures at most bends through these reaches. Preliminary mapping (Figure 6) and analysis suggests that bedrock may provide an important control to adjustment in the mid-reaches of Lockyer Valley. Coupled with drill core data, this can provide important information to alluvial deposition in the Lockyer Valley. From this preliminary collation, it shows that bedrock disappears from the bed at the approximate location of macrochannel confinement, but continues below the bed at a relatively constant slope of 0.35% to the upstream extent. Long profiles of the major tributaries of the Lockyer are currently being collated to compare geomorphic units to the channel bed. It is anticipated that this will yield a regional signature of the process domain for geomorphic formation.

Daryl Lam - Understanding extreme paleofloods in SEQ.


My PhD research involves reconstructing extreme paleoflood events in South East Queensland (SEQ). Briefly it seeks to i) extend temporal records of extreme flood for prediction and mitigation purposes; ii) better understand the upper limits of these extreme events and; iii) identify their climatic drivers. The main focus of this quarter is writing up my confirmation document and developing a clearer framework for the last objective of my research – relationship between climate drivers and extreme floods in the region. I am currently trying to develop hypothesis and questions that I will address in this objective.
 
It is generally accepted that La Nina brings about a wetter phase to the east coast of Australia, but the relationship is not simply linear. Figure 7 shows the relationship between the 20 largest flood events from a 100 year long gauging record from the Mary Catchment and the corresponding ENSO index. While there is some correlation between an increase in sea surface temperature (SST) and extreme flood events (Figure 8), there are other extreme events that have occurred under other settings. For example, the Feb 1992 event (ENSO index @ -4, Figure 7) recorded the 5th highest discharge in the last 100 years at the Miva Station, Mary River. The catchment was saturated by significant rainfall from a nearby cyclone (Daman). As the cyclone moved away from SEQ, another Tropical Low developed in the Coral Sea and a deep trough formed south of the Low running parallel to the coast. These combined to transcend large amount of moisture from the sea onto the mainland. This event was a result of the combination of indirect cyclone activity, saturated catchment, Tropical Low and others. The situation is further complicated by the IPO. Therefore, the relationship between extreme flood events and climatic conditions will be complex. I intend to investigate these complex relationships further and hope to use extreme paleoflood records from my research to improve our understanding the impacts climatic conditions have on extreme flood events. 
Figure 7: The relationship between flood events and La Nina.
Figure 8: Extreme events with SST anonamly.

Heather Haines – Using dendrochronolgy to develop a long-term SEQ rainfall record. 

 
Work on the dendrochronology component of Stage 2 is progressing well.  With the funds from the Wet Tropics Management Authority (WTMA) Student Research Grant that I was awarded I purchased dendrometers to install at both my Lamington National Park and Bunya Mountains National Park study sites.  The Lamington dendrometers have already been installed (see photo above) and the Bunya Mountains installation is taking place October 20-22. These dendrometers will measure daily, seasonal, and annual tree growth which I can then directly compare to climate conditions in the region.  By gaining this understanding of how growth responds to climate I will be able to better predict how the long-term tree ring record I am developing is representative of SEQ climate conditions. Measurements of the Lamington tree-ring samples for my study are ongoing with several long-lived trees being added into the chronology.  I will be traveling to Townsville in November to spend a week discussing my Lamington samples and the patterns observed in Araucaria cunninghamii tree-rings with Dr Nathan English who is both an expert in tropical dendrochronology and my collaborator on the WTMA grant. This will provide me with a greater understanding of climate reconstruction from tropical tree rings and allow me to make progress towards developing a long-term SEQ rainfall record.
 

Jack Coates-Marnane – Marine sediments as archives of climate in SEQ

 
Progress on the use of marine sediments in Moreton Bay as archives of climate in SEQ is being made. Complete data sets of high-resolution analysis of two long sediment cores are almost complete. These include a detailed record of sediment accumulation in central Moreton Bay that allow us to explore regional climate shifts and the impact of recent catchment disturbances on the Bay’s environments. With this information we can contextualize the extent and extremity of the 2011 flood within a longer time-frame. The geochemical characterization of these sediments will also allow us to explore the temporal changes in predominant sources of fine sediments to Moreton Bay. Carbon and nitrogen isotope measurements of sediments provide an insight into the historical impacts of nutrient loading to Moreton Bay and the response of marine algae. We thank Sarah Pausina (who has recently taken maternity leave) for her extensive work on the use of biogenic silica for climate reconstruction. Later this year, we will investigate expanding the use of lower Brisbane river floodplain sediments as archives of past climate and flooding events in SEQ. 

Peyton Lisenby -  Historical channel change in Lockyer Creek. 


Historical channel change analysis for Stage 3 is currently being expanded to include the tributary systems of the Lockyer Catchment. Emphasis of this broader analysis will be placed on tributary channel changes relative to flood events of the 20th and 21st centuries in differing channel environments – macrochannel vs. non-macrochannel. Preliminary investigations indicates that channel changes found outside a macrochannel environment are of a different nature than those changes noted within a macrochannel. Further work will aim to identify the geography and scale of these different populations of channel adjustments, the hydraulic conditions under which the non-macrochannel changes occur, and the influence these changes have on future channel processes. This work will have implications for characterizing sediment connectivity between the tributary and trunk streams and for describing geomorphic effectiveness at the catchment scale. Additionally, this work will aid in determining how the trajectory of river behaviour can change when different channel boundary conditions are imposed, i.e. the absence or presence of macrochannel development. 

Publications 


Baggs Sargood, M. 2013. Hitting rock bottom: Morphological response of upland bedrock-confined streams to catastrophic flooding, BEnvSc Hons, School of Earth & Environmental Science, University of Wollongong.

Croke, J., Fryirs, K., Thompson, C. 2013. Channel-floodplain connectivity during an extreme flood event: Implications for sediment erosion, deposition, and delivery, Earth Surface Processes and Landforms 38 (12): 1444-1456

Croke, J., Reinfelds, I., Thompson, C., Roper, E. 2013. Macrochannels and their significance for flood-risk minimisation: examples from southeast Queensland and New South Wales, Australia, Stochastic Environmental Research and Risk Assessment: 1-14.

Croke, J., Todd, P., Thompson, C., Watson, F., Denham, R. Khanal, G. 2013. The use of multi temporal LiDAR to assess basin-scale erosion and deposition following the catastrophic January 2011 Lockyer flood, SE Queensland, Australia, Geomorphology 184: 111-126.

Grove, J., Croke, J. and Thompson, C. 2013. Quantifying different riverbank erosion processes during an extreme flood event, Earth Surface Processes and Landforms 38 (12): 1393-1406.

Grove J.R., Croke J., Thompson C.J. 2014. Making a difference: examples of the use of repeat LiDAR datasets to guide river management decisions following extreme floods, in Vietz, G; Rutherfurd, I.D, and Hughes, R. (editors), Proceedings of the 7th Australian Stream Management Conference, Townsville, Queensland, pp 109-115. 

Smith, B. 2013. The role of vegetation in catastrophic floods: A spatial analysis, BEnvSc Hons, School of Earth & Environmental Science, University of Wollongong.

Thompson, C., and Croke, J. 2013. Geomorphic effects, flood power, and channel competence of a catastrophic flood in confined and unconfined reaches of the upper Lockyer valley, southeast Queensland, Australia, Geomorphology 197: 156-169.

Thompson, C., Croke, J., Grove, J., Khanal, G. 2013. Spatio-temporal changes in river bank mass failures in the Lockyer Valley, Queensland, Australia, Geomorphology 191: 129-141.

Thompson C., Croke, J., Dent, C. 2014. Potential impacts of levee construction in the Lockyer Valley, in Vietz, G; Rutherfurd, I.D, and Hughes, R. (editors), Proceedings of the 7th Australian Stream Management Conference, Townsville, Queensland, pp 109-115. 

 

Accepted


Croke, J., Denham, R., Thompson, C., and Grove, J. Accepted.  Evidence for self-organised criticality (SOC) in river bank mass failures; a matter of perspective? Earth Surface Processes and Landforms.
 

Submitted


Baggs-Sargood, M., Cohen, T., Thompson, C., and Croke, J. Submitted. Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood. Geological Society of America Bulletin.  
 
Thompson, C., Fryirs, K. and Croke, J. Submitted. The disconnected sediment conveyor belt: Patterns of longitudinal and lateral erosion and deposition during a catastrophic flood in the Lockyer Valley, southeast Queensland, Australia. River Research and Applications.
 

In preparation


Croke, J., Thompson, C., and Grove, J.In prep. "Can we predict erosion during an extreme event using estimates of specific stream power?" Geomorphology.

Dalla Pozza R., and Thompson C.J.
In prep. Specific stream power model for the Burnett catchment – methodology. Department of Science, Information Technology, Innovation and the Arts, Queensland Government,  Brisbane Queensland.

Daley, J.S., Croke,J., Thompson, C., Dalla Pozza R. In prep. Identification and extent of macrochannel features in South-East Queensland, Australia.

Fryirs, K., Lisenby, P. and Croke, J. In prep. Geomorphic responses to a catastrophic flood in a resilient river system: Historical context for the 2011 Lockyer Valley floods. Geomorphology.

Thompson C.J., Croke J., Grove, J. In prep. Channel adjustment in subtropical catchments and the role of bank mass failures. Geomorphology.
Ramona Dalla PozzaSenior Scientist DSITIA, is the newest member of the Big Flood team. For the first half of this year she has been helping with the stream power mapping, but now her role is to communicate the findings of our research to stakeholders, government and the wider community. We welcome your input so if you have innovative ideas on how to communicate or know of events or forums that we should be targeting please contact Ramona: Ramona.DallaPozza@dsitia.qld.gov.au.
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Our mailing address is:
ramona.dallapozza@dsitia.qld.gov.au
Level 4, Building 35, University of Queensland, Brisbane Q 4072

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