BITS Faculty Publications

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Start date: 2000End date: 2009

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    Estimating peak runoff in small catchments
    (Taylor & Francis, 2002-01) Goonetilleke, Ashantha
    The management and design of hydraulic infrastructure requires detailed analysis of the rainfall-runoff process, as well as the allocation of an acceptable level of risk. Risk-based assessment of the rainfall-runoff process requires methodologies that are both accurate and efficient. Although the Rational Method has been a popular analysis tool in risk based assessment, it has many short comings requiring significant subjective judgement by the engineer. Rainfallrunoff models have become increasingly popular in this regard, as they provide accurate tools to predict the deterministic processes taking place in the catchment. A methodology is presented in this paper for incorporating rainfall-runoff models in risk-based assessment that is both efficient in terms of computational effort and accurate. The method relies on the adoption of a storm pattern that embodies the characteristics contained within the statistically based rainfall data that is generally adopted in practice. The methodology has been tested on two hypothetical catchments and 47 small gauged catchments in Queensland. It is shown that using this methodology, statistically based peak runoff can be predicted at all locations in the catchment where suitable catchment subdivision had been undertaken.
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    Modelling pollutant washoff from south-east queensland catchments Australia
    (International Water Association (IWA), 2003) Goonetilleke, Ashantha
    Onsite wastewater treatment systems aim to assimilate domestic effluent into the environment. Unfortunately failure of such systems is common and inadequate effluent treatment can have serious environmental implications. The capacity of a particular soil to treat wastewater will change over time. The physical properties influence the rate of effluent movement through the soil and its chemical properties dictate the ability to renovate effluent. A research project was undertaken to determine the role that physical and chemical soil properties play in predicting the long-term behaviour of soil under effluent irrigation and to determine if they have a potential function as early indicators of adverse effects of effluent irrigation on treatment sustainability. Principal Component Analysis (PCA) and Cluster Analysis grouped the soils independently of their soil classifications and allowed us to distinguish the most suitable soils for sustainable long term effluent irrigation and determine the most influential soil parameters to characterise them. Multivariate analysis allowed a clear distinction between soils based on the cation exchange capacities. This in turn correlated well with the soil mineralogy. Mixed mineralogy soils in particular sodium or magnesium dominant soils are the most susceptible to dispersion under effluent irrigation. The soil Exchangeable Sodium Percentage (ESP) was identified as a crucial parameter and was highly correlated with percentage clay, electrical conductivity, exchangeable sodium, exchangeable magnesium and low Ca:Mg ratios (less than 0.5).
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    A decision support system for site selection of large-scale infrastructure facilities using natural language
    (Australian Society for Operations Research, 2003) Goonetilleke, Ashantha
    Spatial problems are often characterised by incomplete information, multiple conflicting evaluation criteria and a heterogeneous group of decision-makers. Implementation of existing analytical decision–making methods in a Spatial Decision Support System has been characterised by difficulties when dealing with uncertainty, criteria standardization, and group decision-making where there is no consensus. Another problem is the real or perceived difficulty of using such systems, leading to poor uptake by decision-makers. This paper discusses the development of a spatial decision support system (SDSS) using a new natural language approach to mitigate the abovementioned difficulties. The system is designed to aid site selection for large-scale infrastructure facilities at a strategic level, using a fuzzy multicriteria, multi-decision-maker framework and linguistic methods. We describe the theoretical basis of our approach, and its practical implementation in a GIS-based System. A real world site selection problem involving the location of a new industrial facility at Brisbane Airport (Australia) is also worked through.
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    Correlation of soil data with treatment performance of subsurface effluent disposal systems
    (2003) Goonetilleke, Ashantha
    The paper discusses research undertaken to contribute to providing long-term sustainable solutions for on-site sewage treatment based on soil physico-chemical evaluation. The study was conducted within the unsewered area in Logan City Council, Southeast Queensland. The unsewered areas were classified into four different zones based on the future development in the region and environmental sensitivity. Forty eight sampling sites were identified and samples taken from the A and B horizons. The selected soil samples were analysed for a range of physico-chemical characteristics such as pH, electrical conductivity, chloride ion, total nitrogen, total phosphorus, orthophosphate, cation exchange capacity (CEC), individual cations, particle size distribution, organic matter content and mineralogical composition. The soils at the different sites recorded pH levels ranging from moderately acidic to acidic. In the case of CEC, 50% of the sites reported values between 0 and 4 meq/100g, about 30% of the sites reported values from 10 to 47 meq/100g, and the remainder had values between 60 to 90 meq/100g. The data analysis showed that based on location and intended land use, about 70% of the sites investigated had inadequate capability to renovate effluent discharged to the subsurface area from a conventional septic tank. In areas which have a very low cation exchange capacity and low organic matter content, the dominant clay has a low capacity to adsorb the wastewater pollutants. It can be surmised that the use of septic tank/soil absorption systems based on conventional and typical designs would not be feasible. These sites would require extra care in designing and locating of the subsurface on-site disposal system or the use of alternatively designed systems.
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    An experiment with approximate reasoning in site selection using 'infraplanner'
    (Queensland University of Technology, 2003) Goonetilleke, Ashantha
    This paper discusses an application of an intelligent information system for decision-makers involved in multiple criteria group site selection problems under uncertainty. The fuzzy algorithm behind the system was developed by the authors for use in large-scale infrastructure site selection, and is validated here using a site selection problem at Brisbane Airport. The ‘InfraPlanner’ Spatial Decision Support System (SDSS) was created by customising ArcView GIS, and operates on raster data files. The tightly coupled system features linguistic interaction, multiple decision-maker input, uncertainty assessment, and a linguistically controllable aggregation function capable of a variety of compensatory and non-compensatory outcomes. Feedback from decision-makers involved in the experiment indicated a high level of satisfaction with outputs from the system, whilst noting some areas for future development.
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    Information analysis and dissemination for site selection decisions using a fuzzy algorithm in GIS
    (ACTA press, 2003) Goonetilleke, Ashantha
    Site selection for large-scale facilities is often a group multi-criteria decision-making problem under uncertainty. Creating a practical, user friendly, interactive environment for knowledge sharing among decision-makers and stakeholders can contribute significantly to the process by making the optimal solution easier to find, and enabling dissemination of information to affected groups. Existing algorithms for site selection have little or no capability for handling a non-consensus group environment, or to factor quantitative uncertainty into an analysis. This paper presents a new fuzzy algorithm that is practical to implement in raster GIS and suitable for multiple decision-maker site-selection problems under uncertainty. Differing linguistic assessments from decision-makers are combined using a relevance matrix, and quantitative uncertainty is modelled using a method based on type-2 fuzzy sets. Outputs from the algorithm have a high information value as they include measures for conflict, risk and uncertainty, as well as compensatory and non-compensatory aggregated suitability.
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    Mechanical stabilization of unpaved sand roads on fraser island
    (Australian Road Research Board, 2003) Goonetilleke, Ashantha
    Degradation of the road surface quality of the unpaved sand roads of Fraser Island, Queensland, a World Heritage Listed site, occurs because of two major factors. The first is the combined impact of surface runoff from storm events causes water erosion of the road surface, and second is the impact of vehicle tires causes lateral displacement of road surface material. Both processes result in removal of sand from the road surface, a gradual lowering of the elevation of the road surface relative to the surrounding natural forest environment and severe degradation of the road surface. The transported sand blocks stormwater drainage paths and the removal of sand from the road surface results in road closures and reduced access to tourist sites. Mechanical stabilization of the sand pavement is a technique that can assist in minimizing sand loss from the road surface. Laboratory testing of bentonite stabilized sand by varying the percentages of bentonite and moisture content within the sand mixes was undertaken. The effectiveness of bentonite as a sand stabilizer was measured against criteria including optimum bentonite content, optimum moisture content, suction, permeability and CBR. Results obtained to date, indicate that bentonite can significantly improve the load bearing characteristics of the unpaved sand roads. Stabilization of the sand roads using bentonite and compaction, may thus provide a low cost option to increase the bearing capacity of the sand roads in this sensitive environment and thereby provide a sustainable road network in the long term.
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    Modelling unpaved sandy roads on Fraser Island
    (ARRB Transport Research, 2003) Goonetilleke, Ashantha
    This paper briefly reports on the research investigation of sediment transport and overland flow erosion from sandy unpaved roads on Fraser Island. Most of the sediment is transported by bed load because the particles are too coarse to be transported by suspended load. Vehicle traffic, especially 4 WD is considered to be responsible for accelerated erosion. Modelling sediment transport from Fraser Island sandy roads using two generic models: WEPP and KINEROS2 program were carried out. The study reflects that modelling focused on the main factor controlling sediment transport from Fraser Island sandy roads, namely the sediment transport capacity of rill flow can be a very significant tools for natural resource management as well as environmental conservation. Sediment transport capacity of rill flow was tested in the field and collected data were used to calibrate WEPP and KINEROS2. Verification showed that WEPP and KINEROS2 could be used to predict sediment transport capacity on Fraser Island roads.
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    New sustainable concept for sewage treatment technology: Solar energy biological wastewater treatment systems
    (2003, 2003) Goonetilleke, Ashantha
    A novel process for biological nutrient removal and disinfection is developed that is operated at relatively high temperature by making full use of solar energy and internal energy reuse systems. This process, termed solar energy wastewater treatment systems or SEWTS, is designed to achieve substantial ammonia conversion at high reaction rates for on-site wastewater treatment. This study aims to design and construct a prototype for making full use of solar energy to improve the performance of the bio-film reactor by maintaining a relatively high temperature (25-38°C). The basic mechanisms and characters, operating conditions and results of SEWTS are discussed, and some calculation models for solar energy collector design are also shown in this paper. During the six months of the experiment, artificial wastewater and municipal wastewater are treated. The process is shown to be stable, feasible and environmentally friendly.
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    An Investigation into the role of site and soil characteristics in onsite sewage treatment
    (Springer, 2003-04) Goonetilleke, Ashantha
    The onsite treatment of sewage is common in all rural and regional areas of the world. Due to the public health and environmental risks that these treatment systems pose, the need for adopting performance-based management strategies is gaining increasing recognition. This demands the establishment of performance objectives for onsite sewage treatment and disposal which are based on stringent scientific analysis. A research project was undertaken to identify and investigate the role of influential site and soil characteristics in the treatment performance of subsurface effluent disposal areas. The treatment performances of a number of septic systems on a range of site and soil conditions were investigated together with detailed soil analysis. The changes to soil physico-chemical characteristics of the disposal area due to effluent application and its effluent renovation capacity were found to be directly related to the subsurface drainage characteristics. Significant changes to exchangeable cations and chemical parameters such as pH, electrical conductivity and cation exchange capacity (CEC) can result due to subsurface effluent application. A relationship exists between chemical parameters such as exchangeable Na and Ca:Mg ratio and CEC. A strong correlation also exists between the depth to the restrictive subsurface horizon and observed treatment performance. The study confirmed that soil chemistry can be a valuable predictive tool for evaluating the long-term performance of sewage effluent disposal systems particularly in poorly drained sites.