Macrochannels and their significance for flood-risk minimisation: examples from southeast Queensland and New South Wales, Australia

Croke, Jacky; Reinfelds, Ivars; Thompson, Chris; Roper, E.

doi:10.1007/s00477-013-0722-1

Cited by 26 publications

(59 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…e.g. Croke et al 2014 who stressed the importance of geomorphological understanding during flood risk management). Casas et al (2006) argued that coarser resolution will have less consequence when discharge increases, i.e., floodplain areas will be more accurately mapped than near river areas.…”

Section: Discussionmentioning

confidence: 99%

Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models

Brandt

2016

Stoch Environ Res Risk Assess

View full text Add to dashboard Cite

As flood inundation risk maps have become a central piece of information for both urban and risk management planning, also a need to assess the accuracies and uncertainties of these maps has emerged. Most maps show the inundation boundaries as crisp lines on visually appealing maps, whereby many planners and decision makers, among others, automatically believe the boundaries are both accurate and reliable. However, as this study shows, probably all such maps, even those that are based on high-resolution digital elevation models (DEMs), have immanent uncertainties which can be directly related to both DEM resolution and the steepness of terrain slopes perpendicular to the river flow direction. Based on a number of degenerated DEMs, covering areas along the Eskilstuna River, Sweden, these uncertainties have been quantified into an empirically-derived disparity distance equation, yielding values of distance between true and modeled inundation boundary location. Using the inundation polygon, the DEM, a value representing the DEM resolution, and the desired level of confidence as inputs in a new-developed algorithm that utilizes the disparity distance equation, the slope and DEM dependent uncertainties can be directly visualized on a map. The implications of this strategy should benefit planning and help reduce high costs of floods where infrastructure, etc., have been placed in flood-prone areas without enough consideration of map uncertainties.

show abstract

Section: Discussionmentioning

confidence: 99%

Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models

Brandt

2016

Stoch Environ Res Risk Assess

View full text Add to dashboard Cite

show abstract

“…Each site was located within a confined river setting with confinement provided by either bedrock or highly resistant macrochannel banks. Macrochannels, or compound channel-in-channels, have been described in a range of hydrologically variable settings globally (Woodyer, 1968;Graf, 1988;Gupta et al, 1995Gupta et al, , 1999Van Niekerk et al, 1995) and are a common channel form in SEQ (Croke et al, 2013). Macrochannels are characterized by a small inner channel and associated benches set within a much larger channel that operates as a conduit for high magnitude floods (Croke et al, 2016a).…”

Section: Figurementioning

confidence: 99%

“…They have been shown to have large channel capacities, with bank top capacities approaching a 50-year annual recurrence interval (ARI), and are laterally stable because of adjacent, highly resistant, clay-rich Pleistocene alluvium. Results over a range of timescales from post-European to Holocene indicate that lateral migration is limited and changes in cross-sectional area, even postextreme flood events are relatively minor (Croke et al, 2013;Fryirs et al, 2015;Thompson et al, 2016;Lam et al, 2017).…”

Section: Figurementioning

confidence: 99%

Beyond the gorge: Palaeoflood reconstruction from slackwater deposits in a range of physiographic settings in subtropical Australia

et al. 2017

View full text Add to dashboard Cite

The application of palaeoflood hydrology in Australia has been limited since its initial introduction more than 30 years ago. This study adopts a regional, field-based approach to sampling slackwater deposits in a subtropical setting in southeast Queensland beyond the traditional arid setting. We explore the potential and challenges of using sites outside the traditional physiographical setting of bedrock gorges. Over 30 flood units were identified across different physiographical settings using a range of criteria. Evidence of charcoal-rich layers and palaeosol development assisted in the identification and separation of distinct flood units. The OSL-dated flood units are relatively young with two-thirds of the samples being <1000 years old. The elevation of all flood units have resulted in estimated minimum discharges greater than the 1% annual exceedance probability. Although these are in the same order of gauged flood magnitudes, >80% of them classified as 'extreme event'. This study opens up the renewed possibility of applying palaeoflood hydrology to more populated parts of Australia where the need for improved estimation of flood frequency and magnitude is now urgent in light of several extreme flood events. Preliminary contributions to improve the understanding between high magnitude floods and regional climatic drivers are also discussed. Recognised regional extreme floods generally coincide with La Niña and negative IPO phases, while tropical cyclones appear to be a key weather system in generating such large floods.

show abstract

“…The January 2011 flood alone led to the loss of 22 lives in the Lockyer Valley, SEQ (Croke et al 2013). This extreme rain event was followed by ex-tropical Cyclone Oswald in 2013 which produced another major flooding event in SEQ.…”

Section: List Of Figuresmentioning

confidence: 99%

“…Flooding is one of the most devastating hazards to life, the economy and infrastructure in many of the frequency and magnitude of such 'extreme' flood events is needed to evaluate flood risk and guide future planning (Croke et al 2013). …”

Section: Introductionmentioning

confidence: 99%

Extreme flood events in South East Queensland: evidence and implications

Lam¹

View full text Add to dashboard Cite

The use of flood frequency analysis (FFA) to estimate both the magnitude and frequency of the design flood is severely limited by short gauging records. This thesis seeks to improve our understanding of the frequency and magnitude of extreme flood events, with an aim to advance flood risk management and policy planning through the integration of spatial and temporal extreme flood information. This research undertakes a field-work based regional study, collecting slackwater deposits (SWDs) as extreme flood archives and incorporates these as palaeoflood record of extreme flood events for SouthEast Queensland (SEQ).To do so, this study must first define an extreme flood, which is undertaken through the derivation of an Australian Envelope Curve (AEC). The resultant approach represents a significantly improved method to produce an AEC which comprises data from ~2700 gauges in SEQ.An alternative approach to flood frequency is also investigated in the form of a Probabilistic Regional Envelope Curve (PREC) approach which integrates additional spatial information, from homogenous regions. Results indicate that for gauges with either too few, or too many, extreme flood events, the PREC method shows significant changes to the estimated discharges of low % Annual Exceedance Probability (AEP) flood quantiles. A decision making process is provided to ascertain when this method is preferable for FFA.This thesis also examines historical and palaeoflood records that can provide significant upper-tail flood information, often missing from short gauging records. Palaeoflood studies and records have been spatially limited to bedrock settings, in climatic regions outside the subtropical environs of SouthEast Queensland. Reliable historical records are also temporally limited to the last ~200 years of European settlement. This study produced results on the timing and magnitude of past floods from over 30 SWDs across five catchments in the region, spanning a variety of depositional settings, contributing catchment areas, and discharge magnitude. Sensitivity analyses included tests for stable boundary conditions essential for reliable discharge reconstruction. Results show that cross sectional changes due to either aggradation or incision result in resultant changes in discharge that are within the uncertainty range for most of the concerned % AEP flood quantiles.Additional temporal extreme flood information derived from both historical and palaeoflood records are also integrated with gauge records for FFA. This approach reveals that a significant reduction in uncertainty associated with the estimated discharge of a flood quantile can be achieved.Importantly, the uncertainty associated with the 1% AEP flood discharge is reduced by 50-74%. iii

show abstract

Macrochannels and their significance for flood-risk minimisation: examples from southeast Queensland and New South Wales, Australia

Cited by 26 publications

References 17 publications

Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models

Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models

Beyond the gorge: Palaeoflood reconstruction from slackwater deposits in a range of physiographic settings in subtropical Australia

Extreme flood events in South East Queensland: evidence and implications

Contact Info

Product

Resources

About