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Lava dome eruptions are one of the most dangerous forms of volcanic activity. Geophysical, experimental, field or numerical investigations over the past few decades have improved our understanding of dynamic processes associated with these eruptions. In this thesis, I use multi-disciplinary approaches to analyse unrest at four different volcanoes: Volcán de Colima, Unzen, Santiaguito dome complex and Mt. Redoubt. At Volcán de Colima, waveform correlation and seismic interferometry techniques are used to analyse seismic data collected prior to the November 1998 eruption. A decrease in seismic velocity is observed during pre-eruptive activity, consistent with rock failure caused by increased stress associated with the migration of magma towards the surface. This mechanism is confirmed by measurements during experimental Brazil tests on lava samples from the volcano. Furthermore, repetitive micro-cracking during the experiments suggest some repeating earthquakes detected at Volcán de Colima were produced by repeated tensile failure. At Unzen, I analyse seismic data collected during the formation of a lava spine during the last phase of the 1991-95 eruption. Two large groups of repeating earthquakes are identified and further analysis demonstrates how their sources migrated during their period of activation. Citing experimental and field observations, repeated slip motion along the margins of the spine are inferred as the source mechanisms for these earthquakes. Santiaguito dome complex is one of the most active volcanoes in the world, and here I present the first long-term seismo-acoustic dataset to be recorded at the volcano. The dataset captures a major transition in explosive activity that took place in 2015. Variations in energies and waveform arrival times are used to gain insights into the explosion source dynamics. During its eruption in 2009, Mt. Redoubt volcano erupted 19 times, at least 16 of which produced ash plumes tall enough to disrupt air traffic in the region. Using infrasound data recorded during two of these explosions and a three-dimensional plume rise model, I demonstrate how it is possible to efficiently and accurately estimate the ash plume height soon after an eruption begins. These four case studies demonstrate how using a combination of geophysical, experimental, numerical, and field observations can provide more robust interpretations of dynamic processes prior to or during lava dome eruptions. Therefore, multi-disciplinary approaches to studying volcanic activity can have important implications for hazard assessments at active volcanoes worldwide.

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Understanding the urban rainfall-runoff process is an important challenge for the hydrological sciences. Urban areas exhibit a complex mosaic of surface covers, ranging from those of an anthropogenic origin to surfaces of a disturbed natural form, which exhibit varying hydrological behaviours. The urban rainfall-runoff process is managed to reduce the risk of flooding within urban areas, whilst also considering the volume of runoff that downstream water bodies receive. Efforts to understand and manage the urban rainfall-runoff process are often hampered by a lack of rainfall runoff data of sufficient temporal (length and/or frequency) and spatial resolution for locations of interest. Therefore, urban rainfall-runoff processes are typically estimated using hydrological models that attempt to characterise the physical nature of urban areas (using assumptions and estimates of surface hydrological behaviour), that rarely consider how small-scale variations in urban surface cover and hydraulic connectivity influence rainfall-runoff behaviour. This thesis investigates how variations in the physical design, hydraulic form and age of two residential developments of north Swindon (Arley Close and Winsley Close) influence rainfall-runoff behaviour. Through high resolution monitoring of precipitation, drainage flows and soil moisture, a novel understanding of the complex rainfall-runoff properties of urban surface covers is developed, rejecting commonly applied, yet inaccurate assumptions regarding the total imperviousness of urban surfaces. The ability of engineering rainfall-runoff models to replicate the field study site results is assessed to develop an improved understanding of how variations in urban development patterns can be better represented within modelling tools. The implications of inaccurate rainfall-runoff modelling arising from the use of assumptions and estimates within the planning of a retro-fitted surface water drainage storage tank are assessed, demonstrating the importance of developing improved understanding of rainfall-runoff processes at small-scales within the urban environment.

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The migration of fluids in the Earth’s crust embodies the last stage of the internal heat release of our planet. Either spectacularly expressed at the surface through volcanic activity, or more subtly as internal hydrothermal circulation, this phenomenon involves the upwards motion of fluids and magmas that contribute to more efficient heat transfer. On one hand, volcanic eruptions result from the movement of buoyant magmatic liquids towards the surface. On their way up, these magmas cool down, crystallise and upon decompression, build up an internal pressure that dictate the eruptive style: Effusive when the internal pressure is released as it builds up; explosive when the internal pressure accumulates until it is able to fracture the magma. In nature, the shift from effusive to explosive activity is often periodic, reflecting cycles of pressure accumulation and relaxation in the conduit. On the other hand, hydrothermal circulation results from the infiltration of water, of meteoric or magmatic origin, into the rocks making up the crust. Higher temperatures at depth and/ or due to the presence of a magmatic body, trigger the formation of convective cells in which chilled, denser water percolates downwards then heats up, losing density before moving back upwards. Importantly, the circulation of both hydrothermal fluids and magmatic liquids is controlled by the presence of fractures in the crust and the permeability of the surrounding rocks. In this thesis, I first investigate how fractures affect the localisation of fluids in fractured porous rocks through permeability measurements, both at atmospheric pressure and at shallow confining conditions (< 30 MPa; ~1 km depth). I demonstrate that the impact of fractures is greater at lower porosities as the permeability is greatly increased. In more porous rocks, higher pore connectivity means that macro-fractures affect the permeability less significantly, as at least some of the fluid flows through the pre-existing connected porous network. I further demonstrate that, during confinement, most of the mechanical closure occurs at shallow conditions (< 5 MPa; ~200m depth) for the porosity range tested. In addition, I show that mechanically shutting a fracture does not seal the permeable pathways, and that the fractured system is unable to retrieve the same permeability as the intact system. I then develop an analytical solution for the permeability of variably porous, fractured systems as a function of depth before numerically solving it. I complement this work with two “case studies” in which tensile fractures form and open or heal, and link this to the system permeability evolution through time and the implications for magmatic, volcanic and geothermal systems. In the first scenario, tensile fractures open in a cooling magmatic body to form columnar joints in a basalt. Because the temperature at which cooling joints form remains elusive, causing a lingering scientific debate, I develop a novel type of mechanical testing and show for the first time that, in basaltic systems, these macro-fractures form purely in the elastic regime. This is further supported by the use of the rock’s thermo-mechanical characteristics (namely thermal expansion and tensile strength) to model the tensile stress build-up upon cooling and, once formed, the evolution of the fracture width between two columns. Applying the analytical solution for fractured systems permeability defined earlier, I further model the permeability evolution of a columnar jointing magmatic body, important for the understanding of fluid migration during drilling close to magmatic chambers. Finally, in magmas, the entrapment of exsolving gases, during ascent, force the accumulation of stress in the liquid, building pore pressure and potentially resulting in magmatic fragmentation. Consequently, the accumulated stresses can then be dissipated at times longer than the relaxation timescale of the melt, allowing fractures to heal and the system to recover strength lose permeability. Using synthetic glasses in a newly designed experimental setup, I show that the time required to start the healing process is proportional to the relaxation timescale of the melt. I further demonstrate that the kinetics of fracture healing involve two distinct stages. The first stage sees the fracture walls viscously deforming to dissipate excessive energy along the fracture plane (wetting regime), while the second stage consists of the diffusive exchange of elements across the fracture interface (diffusive regime). I finally surmise that the cyclic activity of persistently active silicic volcanoes could be explained by dynamic permeability and strength variations of material due to repeating fracture and healing cycles. Overall, I show that the development and longevity of fractures have significant impacts on the localisation of fluid flow, highlighting that fractures significantly contribute to the development of anisotropy in magmatic, volcanic and geothermal environments. A better understanding of the longevity of fractures in these systems is of prime importance in the mitigation of hazards associated to volcanic eruptions, but also in the development of cheaper, more efficient geothermal energy.

The delivery of Chinese eco-cities has met certain challenges in plan-making and the subsequent implementation of planning documents. Meanwhile, communicative and collaborative planning has been advocated as a method that can assist in decision-making and facilitating urban development in China. In the development of the ‘eco-city’, communicative and collaborative planning has met certain barriers to implementation, and has thus played a limited role in the planning system. This research aims at examining whether a communicative turn has occurred in the delivery of eco-cities with regard to sustainable development in China, discusses how communicative and collaborative planning could help to improve the development of Chinese eco-cities, and examines the methods that can achieve this. To provide an update on the difficulties of communication and collaboration in planning work, the development programmes of the Sino-Singapore Tianjin Eco-city and the Shanghai Dongtan Eco-city are reviewed and compared. The Tianjin Eco-city was approved by central government as one of several pilot areas for developing eco-cities; the Dongtan Eco-city was suspended and failed to achieve its original vision. Data and evidence was collected from the planning documents in both Tianjin and Dongtan, and combined with data collected from interviews with 12 key persons who directly engaged in the delivery of the eco-city programme in China. Along with emerging technologies, local authorities are facing new challenges and opportunities in adopting communicative and collaborative planning. The study concludes that an extensive implementation of communicative and collaborative planning, through both traditional and emerging technologies, is required to reconcile the diverse interests of stakeholders and address the multi-disciplinary issues in the sustainable development of the Chinese eco-city. The major outcome of this study, as the final part of the thesis demonstrates, is a series of recommendations to mitigate issues during the delivery of Chinese eco-cities. According to these recommendations, a practical framework is developed to adopt a communicative rationality in the current Chinese planning system to facilitate the planning process of an eco-city programme in the field of plan-making, implementation, and monitoring. The study also contributes to stakeholder engagement through advancing a modified and innovative approach to dealing with the barriers to communicative activities and consensus building in the development of the eco-city programme in China.

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