Infrastructure Engineering - Research Publications
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ItemScaling from process timescales to daily time steps: A distribution function approach(American Geophysical Union, 2005-02)A new temporal scaling method applicable to many rainfall-runoff-erosion models is presented. The method is based on the probability distribution approach used in a number of spatial hydrological models, and it uses statistical distributions of rainfall intensity to represent subdaily intensity variations in a daily time step model. This allows the effect of short timescale nonlinear processes to be captured while modeling at a daily time step, which is often attractive due to the wide availability of total daily rainfall data. The approach relies on characterizing the rainfall intensity variation within a day using a probability distribution function (pdf). This pdf is then modified by various linear and nonlinear processes typically represented in hydrological and erosion models. The statistical description of subdaily variability is thus propagated through the model, allowing the effects of variability to be captured in the simulations. This results in pdfs of various fluxes, the integration of which over a day gives respective daily totals. The method is tested using 42 plot years of daily runoff and erosion plot data from field studies in different environments from Australia and Nepal. Significant improvements in the simulation of surface runoff and erosion are achieved, compared with a similar model using average daily rainfall intensities. The probability-based model compares well with a subhourly (2 and 6 min) model using similar process descriptions. This suggests that the probability-based approach captures the important effects of sub–time step variability while utilizing commonly available information. It is also found that the model parameters are more robustly defined using the probability-based approach compared with the daily effective parameter model. This suggests that the probability-based approach may offer improved model transferability spatially (to other areas) and temporally (to other periods).
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ItemHydropedology: Synergistic integration of pedology and hydrology(American Geophysical Union, 2006-05-09)This paper presents a vision that advocates hydropedology as an advantageous integration of pedology and hydrology for studying the intimate relationships between soil, landscape, and hydrology. Landscape water flux is suggested as a unifying precept for hydropedology, through which pedologic and hydrologic expertise can be better integrated. Landscape water flux here encompasses the source, storage, flux, pathway, residence time, availability, and spatiotemporal distribution of water in the root and deep vadose zones within the landscape. After illustrating multiple knowledge gaps that can be addressed by the synergistic integration of pedology and hydrology, we suggest five scientific hypotheses that are critical to advancing hydropedology and enhancing the prediction of landscape water flux. We then present interlinked strategies for achieving the stated vision. It is our hope that by working together, hydrologists and pedologists, along with scientists in related disciplines, can better guide data acquisition, knowledge integration, and model-based prediction so as to advance the hydrologic sciences in the next decade and beyond.
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ItemMultiple stable states in hydrological models: An ecohydrological investigation(American Geophysical Union, 2009-03-07)Many physical-based models of surface and groundwater hydrology are constructed without the possibility of multiple stable states for the same parameter set. For such a conceptualization, at the cessation of a transient hydrological disturbance of any magnitude the model will return to the same stable state and thus show an infinite resilience. To highlight and falsify this assumption, a numerical distributed ecohydrological model (coupled hillslope Boussinesq-vertically lumped vadose zone) is presented, in which qualitatively different steady state water table elevations exist for the same parameter set. The multiple steady states are shown to emerge from a positive feedback arising from a reduction in leaf area index (LAI) and thus transpiration, as a saline water table approaches the surface. Limit cycle continuation is also undertaken to quantify the state-space location of the threshold (repellor) between the steady states (attractors) and quantify the resilience. While the model is biophysically simple, it is sufficiently complex to challenge this potentially significant assumption within water resource planning.
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ItemOptimization of a similarity measure for estimating ungauged streamflow(AMER GEOPHYSICAL UNION, 2009-10-17)One approach to predicting streamflow in an ungauged catchment is to select an ensemble of hydrological models previously identified for similar gauged catchments, where the similarity is based on some combination of important physical catchment attributes. The focus of this paper is the identification of catchment attributes and optimization of a similarity measure to produce the best possible ungauged streamflow predictions given a data set and a conceptual model structure. As a case study, the SimHyd rainfall‐runoff model is applied to simulate monthly streamflow in 184 Australian catchments. Initial results show that none of 27 catchment attributes can be safely said to consistently give a better ensemble of models than random selection when used independently of other attributes. This is contrary to prior expectations and indicates the sparseness of information within our database of catchments, the importance in this case of prior knowledge for defining important attributes, and the potential importance of combining multiple attributes in order to usefully gauge similarity. Seven relatively independent attributes are then selected on the basis of prior knowledge. The weight with which each of these attributes contributes to the similarity measure is optimized to maximize streamflow prediction performance across a set of 95 catchments. The other 89 catchments are used to independently test the accuracy of streamflow predictions. Using the optimal set of weights led to marked improvement in the accuracy of predictions, showing that the method, while inferior to local calibration, is superior to alternative methods of model regionalization based on regression and spatial proximity. However, there is evidence of nonuniqueness in the optimal solution and the possibility that the attribute weights are somewhat dependent on the catchments used.
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ItemObject-based classification of ikonos imagery for mapping large-scale vegetation communities in urban areas(MOLECULAR DIVERSITY PRESERVATION INTERNATIONAL-MDPI, 2007-11)Effective assessment of biodiversity in cities requires detailed vegetation maps.To date, most remote sensing of urban vegetation has focused on thematically coarse landcover products. Detailed habitat maps are created by manual interpretation of aerialphotographs, but this is time consuming and costly at large scale. To address this issue, wetested the effectiveness of object-based classifications that use automated imagesegmentation to extract meaningful ground features from imagery. We applied thesetechniques to very high resolution multispectral Ikonos images to produce vegetationcommunity maps in Dunedin City, New Zealand. An Ikonos image was orthorectified and amulti-scale segmentation algorithm used to produce a hierarchical network of image objects.The upper level included four coarse strata: industrial/commercial (commercial buildings),residential (houses and backyard private gardens), vegetation (vegetation patches larger than0.8/1ha), and water. We focused on the vegetation stratum that was segmented at moredetailed level to extract and classify fifteen classes of vegetation communities. The firstclassification yielded a moderate overall classification accuracy (64%, κ = 0.52), which ledus to consider a simplified classification with ten vegetation classes. The overallclassification accuracy from the simplified classification was 77% with a κ value close tothe excellent range (κ = 0.74). These results compared favourably with similar studies inother environments. We conclude that this approach does not provide maps as detailed as those produced by manually interpreting aerial photographs, but it can still extract ecologically significant classes. It is an efficient way to generate accurate and detailed maps in significantly shorter time. The final map accuracy could be improved by integrating segmentation, automated and manual classification in the mapping process, especially when considering important vegetation classes with limited spectral contrast.
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ItemNo Preview AvailableThe proposed heating and cooling system in the CH2 building and its impact on occupant productivity(Australian Institute of Quantity Surveyors, 2005-12-31)Melbourne's climatic conditions demand that its buildings require both heating and cooling systems. In a multi-storey office building , however, cooling requirements will dominate. How the internal space is cooled and ventilation air is delivered will significantly impact on occupant comfort. This paper discusses the heating and cooling systems proposed for the CH2building. The paper critiques the proposed systems against previous experience, both internationally and in Australia. While the heating system employs proven technologies, less established techniques are proposed for the cooling system. Air movement in the shower towers, for example, is to be naturally induced and this has not always been successful elsewhere. Phase change material for storage of "coolth" does not appear to have been demonstrated previously in a commercial building, so the effectiveness of the proposed system is uncertain. A conventional absorption chiller backs up the untried elements of the cooling system, so that ultimately occupant comfort should not be compromised.
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ItemModeling Australian road transport emissions till 2025(The Institution of Engineers, Bangladesh, 2006)The contribution of the road transport sector to local air pollutants is significant in urban areas. Also, road transport has been a major source of greenhouse gases in OECD countries. In Australia, road transport was responsible for 12.9% of total national greenhouse gas emissions in 2000. This paper aims at determining the criteria air pollutants and greenhouse gas emissions from the road transport sector in Australia. Transport activities are projected from a bottom-up approach for a modeling period from 2000 to 2025. Instead of using standard drive cycle emission factors, attempts have been made to quantify real-world on-road emissions. Results have been compared with the findings from existing studies. It was found that the emission of local air pollutants would be decreasing because of the new vehicle emission standards to be adopted and by 2025. CO, HC, NOx and PM10 emissions would be significantly lower than the current level. Among the greenhouse gases, CH4 and N2O emissions are expected to decrease. The tailpipe CO2 emission would stabilize or increase at a very slow rate, because of the expected increase in fuel efficiency. The equivalent CO2 emission considering the global warming potential of CH4 and N2O is also predicted to stabilize.
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ItemNo Preview AvailableAccuracy of satellite measured wave heights in the Australian region for wave power applications(SAGE Publications, 2008-06-01)This article focuses on the accuracy of satellite data, which may then be used in wave power applications. The satellite data are compared to data from wave buoys, which are currently considered to be the most accurate of the devices available for measuring wave characteristics. This article presents an analysis of satellite- (Topex/Poseidon) and buoy-measured significant wave heights for a 1-year period at Cape Sorell and Rottnest Island, off the Australian coast. The analysis found that the satellite-measured wave heights showed a slight positive bias. This is contrary to the findings of most other authors, who have analyzed data from the Northern Hemisphere and generally found a negative bias in the satellite-measured wave heights. The implication is that calibration functions to improve the correlation between the buoy and satellite data may vary for different hemispheres or even regions within these.
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ItemAn evaluation of a proposed ventilation system for Melbourne's CH2 building(Australian Institute of Quantity Surveyors, 2005-12-31)The understanding of ventilation requirements in commercial buildings has been significantly revised in the last 10-15 years. A link between health, productivity and increased fresh air use has been established by some research and this understanding underpins the ventilation philosophy adopted for the CH2 building. The ventilation system design for CH2 that has been evaluated in this paper envisages a mechanically driven system during the day, using the displacement technique to distribute filtered air. All introduced air will be drawn from outside and no recycling of air will occur. Natural ventilation will be employed at night using the stack effect, enhanced by turbine ventilators. This paper critiques the proposed ventilation system in the light of international experience and the particular conditions of the building's location. The evidence suggests that natural ventilation sometimes may be inadequate to achieve the desired objectives. Minimization of indoor pollutants, adequate filtration and high levels of ventilation should, however, ensure satisfactory air quality during occupied hours.
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ItemNo Preview AvailableThermal evaluation of a greenhouse in a remote high altitude area of Nepal(RERIC, 2009-06-01)Remote communities in the high altitude areas of Nepal suffer both chronic and acute malnutrition. This is due to a shortage of arable land and a harsh climate. For seven months of the year, the harvesting of fresh vegetables is almost impossible. Greenhouse technology, if appropriate for the location and its community, can extend the growing season considerably. Experience in the Ladakh region of India indicates that year-round cropping is possible in greenhouses in cold mountainous areas. A simple 50-m 2 greenhouse has been constructed in Simikot, the main town of Humla, northwest Nepal. This paper describes the evaluation of the thermal performance of that greenhouse. Both measurement and simulation were used in the evaluation. Measurements during the winter of 2006-7 indicate that the existing design is capable of producing adequate growing conditions for some vegetable crops, but that improvements are required if crops like tomatoes are to be grown successfully. Options to improve the thermal performance of the greenhouse have been investigated by simulation. Improvements to the building envelope such as wall insulation, double-glazing and using a thermal screen were simulated with a validated TRNSYS model. The impact of the addition of nighttime heat from internal passive solar water collectors was also predicted. The simulations indicate that the passive solar water collectors would raise the average greenhouse air temperature by 2.5°C and the overnight air temperature would increase by 4.0°C. When used in combination, overnight temperatures are predicted to by almost 7°C higher.