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Accueil du site → Master → Australie → Evaluating an asymmetric microrelief system designed to secure soil, water and biocapacity in eroded, degraded and modified peri-urban landscapes

University of Newcastle (2016)

Evaluating an asymmetric microrelief system designed to secure soil, water and biocapacity in eroded, degraded and modified peri-urban landscapes

Stevens, Peter R.

Titre : Evaluating an asymmetric microrelief system designed to secure soil, water and biocapacity in eroded, degraded and modified peri-urban landscapes

Auteur : Stevens, Peter R.

Université de soutenance : University of Newcastle

Grade : Master of Philosophy (MPhil) 2016

Résumé
This research fills a gap in the knowledge of microrelief as a tool for recovering degraded land, and adds to the knowledge with a new and original contribution. The literature on surface microrelief, one of the major factors that control stormflow, surface runoff, and related ecosystems functions, including soil formation, was reviewed in the global and peri-urban context. It was concluded that anthropogenic development exacerbates stormwater flow, soil erosion and biodiversity losses. The conventional response is to harden and drain the land, depleting ecosystem functions and denying water from the soil. Trends in stormwater, erosion control and urban water cycle management within water sensitive design thinking (WSD) and the prevailing catchment drainage paradigm were reviewed and found inadequate for addressing erosion, which continues at many hundreds of times the rate of soil formation. Australian legislation requires ecologically sustainable development and ‘the maintenance of ecosystems that sustain life’. This requirement is not being met. Soils, biological capacity and local water cycles are depleted by anthropogenic development. It was hypothesised that an asymmetric microrelief system (AMS) based on natural systems could be designed to arrest stormflows and stem soil erosion. The AMS implemented on the Callaghan Campus of the University of Newcastle Australia in 1992 was evaluated with an industry standard conceptualisation modelling tool MUSIC v5 (eWater 2013) based on site data gathered over four years (2011-2015). Soils were assessed for permeability with infiltrometers and a hydraulic penetrometer under dry and saturated conditions. AMS on-ground performance, vegetation cover and soil profiles were photographically recorded. Results from modelling and site observations of the UoN AMS case after twenty years, and the subsequent Allowah case after 6 months, demonstrated that a scalable AMS can be designed on the basis of remnant soil character, rainfall intensity and slope, and implemented with local tools and resources to rejuvenate degraded peri-urban lands, by dissipating rainfall energy, reducing loss of water, sediment and nutrient by > 90%, and by securing > 60% of peak stormflows in < 8% of the land area. The modelling tool was found to have limitations in regard to the complex patternation of AMS Bionodes. The results point to the need for a refined modelling and specification tool with the capacity to integrate complex microrelief patternation, biological processes and the local, climate moderating water cycle. There is the opportunity to take a new approach to land use planning and ecologically sustainable development (ESD) based on the fluid patterns of exaggerated microrelief found in the naturally hydrated landscape mosaic. The likely benefits, savings and wider implications are discussed. These include reduced risk ; reduced high exposure maintenance liabilities ; reduced disaster recovery costs ; reduced pollution of aquatic ecosystems ; the recovery of arable land with a net positive rate of organic soil formation ; the rejuvenation of climate moderating biomass ; an integrated ‘whole of system’ response to flooding, and increasing biological capacity on the urban fringe. There are implications for all planners and land managers. The research shows that microrelief is a practical and affordable tool for rehydrating the legacy of degraded lands in Australia deemed ‘beyond the means of the nation’ to repair.

Mots clés : microrelief ; landscape hydration mosaic ; landscape hydration ; landscape rehabilitation

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Page publiée le 12 mars 2018