Environmental Research Institute of the Supervising Scientist

Darwin, Australia

Environmental Research Institute of the Supervising Scientist

Darwin, Australia
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Whiteside T.G.,Environmental Research Institute of the Supervising Scientist | Maier S.W.,Charles Darwin University | Boggs G.S.,Wheatbelt NRM Inc
International Journal of Applied Earth Observation and Geoinformation | Year: 2014

Geographic object-based image analysis (GEOBIA) produces results that have both thematic and geometric properties. Classified objects not only belong to particular classes but also have spatial properties such as location and shape. Therefore, any accuracy assessment where quantification of area is required must (but often does not) take into account both thematic and geometric properties of the classified objects. By using location-based and area-based measures to compare classified objects to corresponding reference objects, accuracy information for both thematic and geometric assessment is available. Our methods provide location-based and area-based measures with application to both a single-class feature detection and a multi-class object-based land cover analysis. In each case the classification was compared to a GIS layer of associated reference data using randomly selected sample areas. Error is able to be pin-pointed spatially on per-object, per class and per-sample area bases although there is no indication whether the errors exist in the classification product or the reference data. This work showcases the utility of the methods for assessing the accuracy of GEOBIA derived classifications provided the reference data is accurate and of comparable scale. © 2013 Elsevier B.V.

Fryirs K.,Macquarie University | Brierley G.J.,University of Auckland | Erskine W.D.,Environmental Research Institute of the Supervising Scientist | Erskine W.D.,University of Newcastle
Earth Surface Processes and Landforms | Year: 2012

Applications of ergodic reasoning (or location for time substitution) aid efforts at environmental reconstruction and prediction, providing a useful tool to analyse and communicate stages of landscape evolution. Analysis of the historical range of behaviour and change that a river system has experienced can be used to interpret thresholds that have been breached, and underlying controls and/or triggers for adjustment and change. This information can be used to forecast future trajectories of adjustment and provide target conditions for management activities. This paper uses a case study from upper Wollombi Brook, New South Wales, Australia to demonstrate how ergodic reasoning can be used to assess river behaviour, change and responses to natural and human-disturbances. The 'river evolution diagram' developed by Brierley and Fryirs (Geomorphology and River Management: Applications of the River Styles Framework. Blackwell Publishing: Oxford, 2005) is presented as a means for depicting the range of behaviour and evolutionary variability of this river. These approaches can be readily applied in other systems. Implications for approaches to analysis of river evolution and management are outlined. © 2012 John Wiley & Sons, Ltd.

Erskine W.D.,Environmental Research Institute of the Supervising Scientist | Erskine W.D.,University of Newcastle | Saynor M.J.,Environmental Research Institute of the Supervising Scientist
Journal of Hydrology | Year: 2013

Rainfall, discharge and bedload were measured at three gauging stations (East Tributary, Upper Swift Creek and Swift Creek) in the Ngarradj Creek catchment at Jabiluka, Northern Territory, Australia. Hand-held, pressure difference, Helley-Smith bedload samplers were used to measure bedload fluxes for the 1998/1999, 1999/2000, 2000/2001 and 2001/2002 wet seasons. Rainfall is strongly seasonal over the Ngarradj Creek catchment, being concentrated in the wet season between November and April. Mean annual point rainfall between 1998 and 2007 for the water year, September to August, inclusive varied over the Ngarradj Creek catchment from 1731±98mm (SE) to 1754±116mm. Between 190 and 440mm of rainfall are required before streamflow commences in December in most years. Streamflow persists until at least April. Mean annual runoff, as a percentage of mean annual rainfall, decreases slightly with increasing catchment area. Bedload ratings were calculated for four data sets. Significant bedload ratings were defined as those that were not only statistically significant (ρ0.05) but also explained at least 0.60 of the variance in bedload flux. For the three stations, twenty-three bedload ratings complied with the above criteria. Sixteen equations were accepted for East Tributary, four bedload ratings were accepted for Upper Swift Creek and three bedload ratings were accepted for Swift Creek. Significant bedload ratings were established between bedload flux and discharge, unit bedload flux and discharge, transport rate of unsuspended bedload by immersed weight per unit width and time and both unit and excess unit stream power, and finally, adjusted submersed bedload weight and both unit and excess unit stream power for raw and log10-transformed data. 'Censored data sets' were compiled for Upper Swift Creek and Swift Creek to include only bedload fluxes measured when there was no apparent scour or fill so that there were no changes in sand supply from the catchment (i.e. equilibrium conditions).Bedload sediments are similar at all sites. There is little difference in grain size statistics between wet season bedload and dry season bed material. The differences which were significant suggest that most of the bed material is transported as bedload during the wet season. Size selective transport occurs at all three gauging stations with bedload being better sorted than bed material and the coarsest fraction (Cobble gravel) is mobile only during extreme events. © 2013.

Erskine W.D.,Environmental Research Institute of the Supervising Scientist | Erskine W.D.,University of Newcastle
Hydrological Processes | Year: 2013

A rainstorm on 27-28 May 2003 caused a debris slide in the fill batter of a recently constructed road crossing of a zero-order stream in Compartment 107, Chichester State Forest, Australia. The slide became more liquid downslope, changing to a debris flow. This flow completely blocked the inlet of the next downstream road crossing of the same stream, where it had changed to first order. Gullying of the downstream fill batter at the second crossing was caused by water flowing over the road. The estimated volume of sediment removed by the upslope debris slide was 350m3, and the estimated erosion volume by gullying of the downstream fill batter at the second crossing was 100m3. Mass movements have occurred in Compartment 107 before any forestry activities because of the presence of colluvium-filled bedrock depressions. Furthermore, the channel downstream of the second crossing has transported much larger quantities of coarser sediment than what was mobilized during and after the event of 27-28 May 2003. Channel bank exposures reveal up to 2.5-m-thick, poorly sorted gravels, which, on the basis of soil development in the overlying deposits, appear to be older than 200years. Sediment was deposited in the channel downstream of the second crossing, as determined using Munsell Soil Colour as a fingerprinting technique. The volumes involved were relatively minor and were only deposited in slackwater areas as spatially disjunct, relatively thin patches. Sediment was restricted to the first 500m downstream of the second crossing and was unlikely to have reached the main stream, Allyn River, in any measurable quantity. The channel downstream of the second road crossing is a high-energy feature because it contains a range of channel units (waterfalls, bedrock, boulder and log steps, cascades, etc.) formed by erosion of resistant materials. Similar and larger events to that of 27-28 May 2003 in the following 13 months did not cause further road erosion, indicating that the installed rehabilitation measures stabilized the road. © 2012 John Wiley & Sons, Ltd.

Hancock G.R.,University of Newcastle | Evans K.G.,University of Newcastle | Evans K.G.,Environmental Research Institute of the Supervising Scientist
Earth Surface Processes and Landforms | Year: 2010

Understanding landscape features such as gullying and soil erosion is an important issue in the long-term dynamics and evolution of both natural, agricultural and rehabilitated (i.e. post-mining) landscapes. Considerable research has been undertaken examining the initiation, movement and overall dynamics of such features. This study reports on a series of 34 gully heads and other erosion features, such as scour holes (five in total), located in channels in a catchment largely undisturbed by European activity in the Northern Territory, Australia over a 5 year period (2002-2007). During this period the erosion features were monitored for their headward advance/retreat, enlargement or in-filling. The erosion features ranged in depth from 0.2 m to 1.5 m and widths of 0.3 m to 8 m. Hillslope erosion was also monitored using erosion pins. The catchment was subject to a range of rainfall regimes including extreme rainfall and a Category 5 cyclone and also was burnt every second year so that all grass cover was removed according to traditional management practice. The results of this monitoring show that the erosion features have changed little during this 5 year period. A remote sensing assessment found no relationship between erosion feature morphology and hillslope erosion. The monitored gullies heads and scour holes appear to be resilient landscape features, yet have a morphology that suggests they are ready for rapid headward movement and expansion, leading to a destabilisation of the catchment. Hillslope erosion was found to be related to wetness indices derived from a digital elevation model. Significant linkages were found between hillslope erosion and change in erosion feature depth, indicative of a strong hillslope-channel coupling. Copyright © 2010 John Wiley & Sons, Ltd.

Erskine W.D.,University of Newcastle | Erskine W.D.,Environmental Research Institute of the Supervising Scientist
Australian Geographer | Year: 2011

Historical planform changes in a 14.7 km reach of the lower Pages River were determined to assess whether they were autogenic (inherent in the river regime) or allogenic (driven by external changes) in nature so as to better focus river management activities and river restoration works. A pattern metamorphosis or complete change in river morphology occurred during the February 1955 flood. The peak discharge of this event exceeded the slope and grain size (intrinsic) threshold for braiding, converting the narrow, slightly sinuous stream to a wide, braided-like river. Five subsequent intrinsic threshold exceeding floods did not cause further bar development because an over-widened channel already existed. Autogenic channel planform changes included sinuosity variations due to lateral migration and pattern metamorphosis due to the exceedance of a discharge-slope-grain size geomorphic threshold. Allogenic channel planform changes included: (1) realignment/channel straightening and artificial cutoffs by river training works; (2) lateral migration by increased bank erodibility due to riparian vegetation clearing; (3) lateral migration by the operation of a transitive geomorphic threshold involving the onset of a flood-dominated regime after 1946 and increased catchment runoff after 1830 due to large-scale clearing of catchment vegetation; and (4) the occurrence of a large flood in February 1955. Multiple forcing factors have clearly caused historical channel planform changes of the lower Pages River, making the design of river management and restoration works a complex matter outside the scope of simple formulaic protocols. © 2011 Geographical Society of New South Wales Inc.

Bayliss P.,Environmental Research Institute of the Supervising Scientist | van Dam R.A.,Environmental Research Institute of the Supervising Scientist | Bartolo R.E.,Environmental Research Institute of the Supervising Scientist
Human and Ecological Risk Assessment | Year: 2012

The Ranger uranium mine is surrounded by the World Heritage Kakadu National Park, Australia, and is upstream of the Ramsar-listed wetlands of the Magela Creek floodplain. We present the results of a Quantitative Ecological Risk Assessment (QERA) for the floodplain that combines both point source mining risks and diffuse non-mining landscape-scale risks. A high level of protection for the biodiversity of aquatic ecosystems was used as the assessment endpoint. Mining risks in the surface water pathway were assessed for four key mine-associated solutes (uranium, manganese, magnesium, and sulphate), and non-mining landscape-scale risks were assessed for weeds, feral pig damage, unmanaged dry season fire, and saltwater intrusion from potential sea-level rise due to climate change. Results show that non-mining landscape-scale risks are currently several orders of magnitude greater than risks from mine water contaminants. A weed (Para grass; Urocloa mutica) is the major ecological risk because of its extent, effect, and rapid spread rate. The QERA was incorporated into a Bayesian Belief Network to help evaluate different management strategies. We conclude that non-mining landscape-scale risks to the floodplain should receive the same level of close scrutiny and investment as that applied to uranium mining risks. © 2012 Taylor and Francis Group, LLC.

Hancock G.R.,University of Newcastle | Murphy D.,University of Western Australia | Evans K.G.,University of Newcastle | Evans K.G.,Environmental Research Institute of the Supervising Scientist
Geoderma | Year: 2010

The role of geomorphology in relation to the spatial and temporal distribution of soil carbon is of considerable interest in terms of landscape management and carbon sequestration. Soil carbon plays an important role in soil water holding capacity, soil structure and overall soil health. Soil is also a significant store of terrestrial carbon. This study examines total soil carbon (SC) concentration at the hillslope and catchment scale in the Tin Camp Creek catchment, Arnhem Land, Northern Territory, Australia. The catchment is largely undisturbed by European agriculture or management practices and is located in the monsoonal tropics. Results show that SC concentration along hillslope transects has remained consistent over a number of years and it is strongly related to hillslope position and topographic factors derived from precision surveying and provides a baseline assessment. Poor relationships were found when using a good quality medium resolution digital elevation model to derive topographic factors. This finding demonstrates the need for high resolution survey data for the prediction of total C at the hillslope and catchment scale. There was little difference in SC concentration between years and overall, SC down the hillslope profile varies little temporally suggesting that concentrations are relatively stable in this environment. An assessment of the relationship between SC and soil erosion using 137Cs and erosion pins demonstrates that sediment transport and deposition play little role in the distribution of SC in this environment. Vegetative biomass appears to be the major contributor to SC concentration with vegetative biomass being strongly controlled by topographic factors. While the SC concentration is constant over the study period further sampling is required to assess decadal trends. Crown Copyright © 2009.

Van Dam R.A.,Environmental Research Institute of the Supervising Scientist | Harford A.J.,Environmental Research Institute of the Supervising Scientist | Warne M.S.J.,Water Quality and Aquatic Ecosystem Health
Integrated Environmental Assessment and Management | Year: 2012

The use of the no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) in ecotoxicology has been consistently criticized for over 30 years. A search of the literature from the past 30 years found 22 articles challenging the validity and/or appropriateness of NOEC/LOEC data compared to only one in defense of such data. Notwithstanding this compelling weight of evidence, the NOEC and LOEC remain commonly published measures of toxicity from ecotoxicological studies. In this article we argue that the major reason for the continued generation and publication of NOEC/LOEC data is that key government and intergovernmental organizations have been ''sitting on the fence'' on the issue for more than a decade. Although most key environmental qualityguideline, toxicity testing, and associated guidance documents have now recognized the limitations of NOEC/LOEC data, to date no such document or standard toxicity test method has formally ceased recommending or providing guidance on the generation of such data. This is a problem because it is these very guidance documents and test methods that regulatory agencies demand be used by industry for regulatory activities, and on which commercial testing facilities attain and maintain their testing accreditation. Consequently, there will be little impetus for change to statistical analysis practices unless changes to the key guidance documents and test methods necessitate it. Although some progress on this has been made (e.g., in Canada, Australia and New Zealand), there needs to be stronger and universal action to ensure NOEC/LOEC data are no longer generated. ©2012 SETAC.

Whiteside T.G.,Environmental Research Institute of the Supervising Scientist | Bartolo R.E.,Environmental Research Institute of the Supervising Scientist
International Journal of Applied Earth Observation and Geoinformation | Year: 2015

The Ramsar-listed wetlands of the Magela Creek floodplain, situated in the World Heritage Kakadu National Park, in northern Australia are recognised for their biodiversity and cultural values. The floodplain is also a downstream receiving environment for Ranger uranium mine, which is entering closure and rehabilitation phases. Vegetation on the floodplain is spatially and temporally variable which is related to the hydrology of the region, primarily the extent and level of inundation and available soil moisture. Time-series mapping of the floodplain vegetation will provide a contemporary baseline of annual vegetation dynamics to assist with determining whether change is natural or a result of the potential impacts of mine closure activities such as increased suspended sediment moving downstream. The research described here used geographic object-based image analysis (GEOBIA) to classify the upper Magela Creek floodplain vegetation from WorldView-2 imagery captured over four years (2010-2013) and ancillary data including a canopy height model. A step-wise rule set was used to implement a decision tree classification. The resulting maps showed the 12 major vegetation communities that exist on the Magela Creek floodplain and their distribution for May 2010, May 2011, June 2012 and June 2013 with overall accuracies of over 80% for each map. Most of the error appears to be associated with confusion between vegetation classes that are spectrally similar such as the classes dominated by grasses. Object-based change detection was then applied to the maps to analyse change between dates. Results indicate that change between dates was detected for large areas of the floodplain. Most of the change is associated with the amount of surface water present, indicating that although imagery was captured at the same time of year, the imagery represents different stages of the seasonal cycle of the floodplain. © 2015 Elsevier B.V.

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