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University of Queensland (2008)

Modelling Land Susceptibility to Wind Erosion in Western Queensland, Australia

Webb Nicholas

Titre : Modelling Land Susceptibility to Wind Erosion in Western Queensland, Australia

Auteur : Webb Nicholas

Grade : Doctor of Philosophy (PhD) 2008

Université de soutenance : University of Queensland

Résumé partiel
Wind erosion is a land degradation process with global consequences. Understanding spatial and temporal patterns in land susceptibility to wind erosion is essential for integrating wind erosion research across scales and enhancing management strategies to control potential land degradation. There are significant gaps in our knowledge of which areas of the Earth’s surface are susceptible to wind erosion, and how the erodibility of land changes through time in response to climate variability and land management pressures. This stems from a lack of research into spatial and temporal patterns of land erodibility, particularly at the landscape to regional scales (103 to 104 km2). This thesis addresses these knowledge gaps by presenting research into the development and application of a model to assess land susceptibility to wind erosion in the rangelands of western Queensland, Australia. The foundation for a new Australian Land Erodibility Model (AUSLEM) is established through a systems analysis of the factors controlling wind erosion, and a review of approaches for representing land erodibility in wind erosion modelling systems. The thesis explores how meteorological, soil and vegetation conditions affect the susceptibility of land to wind erosion, synthesising the analysis in a conceptual model of the land erodibility continuum. The conceptual model provides the basis for a review of wind erosion models that are applicable from the paddock (103 m2) to regional (104 km2) and global scales. Current limitations to modelling soil and land erodibility are evaluated and the thesis identifies research priorities for developing new models to predict land susceptibility to wind erosion. The lack of robust schemes to model temporal changes in soil erodibility adversely affects the performance of wind erosion models. To address this issue, a framework was developed for modelling temporal variations in soil erodibility. The framework is an approach for assessing temporal responses of soils to short-term (event-based) variations in climate and land management conditions. Application of the model was restricted by a lack of quantitative data to parameterise the model functions. To address the issue, the thesis presents an analysis of the current status of soil erodibility research and outlines priorities for future research into soil erodibility dynamics.AUSLEM was developed as a Geographic Information System tool to assess land susceptibility to wind erosion across western Queensland, Australia. The model operates at a 5 x 5 km spatial resolution on a daily time step, using inputs of grass and tree cover, soil moisture, soil texture and surficial stone cover. Model performance was evaluated by comparing trends in the model output with trends in wind speeds and observational records of dust events recorded at eight meteorological stations in western Queensland between 1980 and 1990. The validation was conducted at four spatial length scales, from 25 to 150 km. Results show that AUSLEM performs well in the arid southern and western regions of the study area. Poor model performance at scales <102 km2 is linked to the lack of a scheme to predict temporal variations in soil erodibility. The approach for validating AUSLEM was shown to be highly dependent on the types of dust events used for the comparison, calling for additional methods for assessing model accuracy. This was addressed through the development of a method for visually assessing land erodibility at the landscape scale using long distance (103 km) vehicle-based transects. Visual assessments of land erodibility in western Queensland were collected and then used in a secondary validation of AUSLEM. The results confirm that the model performs well in the west of the study area in the open rangelands. In regions with heterogeneous woody vegetation cover the model performance decreases, demonstrating the importance of considering the spatial

Mots-clés : wind erosion, erodibility, dust, rangelands, model, assessment, Australia

Présentation et version intégrale (pdf 29,7 MB)

Page publiée le 24 mai 2011, mise à jour le 15 juillet 2017