There is growing concern that the adoption of intensive agricultural land management practices in upland areas of the UK over the past 50-60 years may have affected hydrological responses and sediment transfer regimes in river catchments and could, therefore, be contributing to increased levels of flood risk and ecological disturbance. However, recent evidence from a research catchment at Pontbren in mid-Wales indicates that the implementation of a more sustainable livestock farming strategy could help to mitigate some of these impacts, raising the possibility that strategic land use planning could be used as a cost-effective, multi-functional river management option. The impacts of historical land use changes and land management practices on contemporary sediment dynamics in the study area are explored in this thesis through a system approach which acknowledges the importance of interrelationships between hydrological and geomorphological processes. Results from hydrological experiments and modelling exercises are used to inform analyses of spatial and temporal variation in sediment production and transfer from a variety of potential sources. Grazed, agriculturally-improved pastures were found to supply fine material to stream channels via both surface runoff and field drains. In particular, drain-derived sediment is likely to represent an important component of the total fine sediment yield in subcatchments where agricultural intensification has been widespread. Agricultural drainage ditches were also found to act as sources of sediment in such areas, along with eroding channel banks. Sediment production from bank sources may relate to historical changes in peak flows caused by agricultural intensification. Stream sediment yields are strongly related to differences in sediment supply from the aforementioned sources and could therefore be reduced by limiting mobilisation at the point of origin within the landscape. In terms of channel-derived material, this could be achieved through peak flow reductions associated with woodland and hedgerow restoration.

This research concentrates on two study areas.  A family of blowout pipes from North Namibia imaged in 3D seismic data; and a group of large buried pockmarks and a field of small seabed pockmarks from the Western Nile Deep Sea Fan (NDSF) imaged in ultra high resolution 2D data.  The general themes of this research are pipe and pockmark morphology and formation process, their spatial and temporal distribution and the magnitude and frequency of fluid flux through the conduit. A family of blowout pipes from Namibia exhibit a variety of seismic characteristics, with the largest pipes containing a blowout crater and evidence of possible stacked palaeo-pockmarks. Pipe formation is shown to be intermittent and persistent throughout the Neogene. The spatial position of pipes adheres to both basinal and local controls. A group of large buried pockmarks on the NDSF are interpreted to have formed between 15,000 yrs BP and 125,000 yrs BP, the majority of which are believed to have formed at the same time c. 60,000-80,000 yrs BP.  These buried pockmarks show evidence for highly focused, episodic fluid flow following burial of the pockmark.  The longevity of post formation fluid migration is estimated to be ~50,000-100,000 yrs. A field of > 13,800 small seabed pockmarks (Nile Deep Sea Fan) are interpreted to have formed within the last 1,000 yrs.  Spatial statistics identified an exclusion zone or drainage cell surrounding each pockmark which is not penetrated by the formation of any other pockmark.  A conceptual model for a drainage cell is proposed whereby pockmark formation dissipates, a radius/area of fluid and overpressure, thereby preventing the formation of another pockmark within that cell.

From 2010 The Flood and Water Management Act has given the Environment Agency and local authorities in the United Kingdom a statutory requirement to manage flooding from groundwater. A robust, long-term groundwater flood risk assessment methodology was developed using the Pang/Lambourn catchment in West Berkshire as a case study. A recharge model based on a soil moisture budget was built in GIS and tested against observations. The timing and mechanism of flow in the vadose zone was also assessed using cross-correlation analysis between rainfall and borehole responses for a better understanding of recharge processes. Regional MODFLOW models were developed for saturated groundwater flow using input from the recharge model. This integrated model was then coupled with a Global Climate Model using a stochastic weather generator to downscale output to the catchment. An ensemble of high and low climate change scenarios suggests there will be between a 5.5% and 27% reduction in recharge over the coming century and mean groundwater levels will lower by up to 3.8%. Land use modification characterised by afforestation and urbanisation resulted in nuanced changes in the spatial distribution of recharge as well as a further mean reduction of 6.8% on top of the climate change impacts. Groundwater flood hazard maps were developed and integrated with a social vulnerability index to identify 1.7 km2 of the Pang/Lambourn at high risk. In the Pang catchment this represents around 1400 properties. Climate and land use change scenarios suggest however that the risk of groundwater flooding in the catchment will decrease considerably (25-98%) over the next century. This reduction in risk is likely to make mitigation through targeted land use modification unnecessary.

This thesis aims to improve the current understanding of the processes which control the flow variability of Greenland Ice Sheet (GrIS) outlet glaciers. The most recent Intergovernmental Governmental Panel on Climate Change (IPCC) report (Meehl et al., 2007) identifies that a critical limitation to forecasts of sea-level rise are uncertainties in modelling the ice dynamics of the GrIS. Using Synthetic Aperture Radar (SAR) feature tracking, seasonal velocities of land- and marine- terminating glaciers in a region in the northeast of Greenland are measured. Records of air temperature in conjunction with seasonal observations of supraglacial lake development, sea ice conditions and ice front positions, derived from SAR imagery, are used to investigate the controls on the observed variations in ice velocity. A clear link between ice velocities and glacier hydrology is found. These findings are consistent with observations from other glaciers in Greenland and are suggestive of a universal hydrological forcing of ice velocity for the whole of the GrIS ablation zone. Lake drainage events have been identified as a key factor in linking atmospheric changes, glacier hydrology and ice velocities in Greenland. For modelling purposes, a means of parameterising the distribution and evolution of supraglacial lakes is therefore needed. Assuming that water will pond in surface depressions, this thesis assesses the ability of using Digital Elevation Models (DEMs) for this purpose. High resolution DEMs are created using Interferometric SAR (InSAR) for two, separate regions of the GrIS. The positions and areal extent of surface depressions are compared with those of lakes observed in optical satellite imagery. The level of correspondence between the two datasets is found to be poor as a result of the resolution of the DEMs and the physical differences between surface depressions and lakes (e.g. lakes may not fill the capacity of the depression). An alternative method for parameterising the seasonal distribution of supra-glacial lakes, by extrapolating trends observed in current lake distributions, is investigated. The locations and evolution of lakes in the west of Greenland during the summer of 2003 are mapped using 47 Moderate Resolution Imaging Spectroradiometer (MODIS) images. Clear trends are identified in the distributions of lakes with elevation and are linked to the seasonal melt-cycle and to changes in ice thickness and its influence on surface depressions, tensile stresses and hydrofracturing. It may be possible to extrapolate these trends to other regions and higher elevations on the ice sheet, thereby enabling the distribution of lakes to be parameterised in ice sheet models. The findings of this thesis help to contribute to the understanding of the interaction between climate and ice dynamics in the context of the GrIS.

No description available.

In this study, an isotope dilution method specifically designed to detect anaerobic methane oxidation (AOM) in methanogenic wetland soils was developed.  A range of anaerobic soils and sediments were screened for AOM potential.  Methane and carbon dioxide emissions were investigated in strictly anoxic microcosms to which ¹³C-labelled methane was added, and changes in the concentration and ¹²C/¹³C isotope ratios of methane and carbon dioxide were subsequently measured and used to calculate the separate components of the methane flux.  The results indicated that certain soils can oxidise methane oxidation anaerobically.  The clearest evidence for AOM was provided by minerotrophic fen soil (pH 6.0) in Bin Forest, which is derived from ultra-basic and serpentine till.  In the Bin Forest fresh soil anoxic microcosms, net consumption of methane was observed, and the amount of headspace ¹³C-CO₂ increased at a greater rate than the ¹²⁺¹³C-CO₂, further proof of methane oxidation.  Net methane production was observed in soil from Murder Moss, an alkaline site, pH 6.5, with a strong calcareous influence, but the ¹³C-CH₄ and ¹³C-CO₂ data indicated co-occurrence of AOM in this soil.  Anaerobic methane oxidation was not observed in the other, lower pH soils.  There was no evidence that amending anoxic slurries with up to 5.0 mM sulphate or  nitrate solutions promoted anaerobic methane oxidation.  Overall, this study provided good evidence for anaerobic methane oxidation in some wetland soils, and suggested that models predicting methane flux from wetland soils to the atmosphere could be improved by better understanding of the process.

The geological and geodynamic processes that have controlled the evolution of the Northumberland Trough Region in Northern England have been investigated to expand understanding of the evolution of continental extensional basins. The region has experienced a number of extensional, compressional and wrench tectonic events throughout Late Palaeozoic, Mesozoic and Cenozoic times. These events have led to a complex subsidence and uplift history. A kinematic model has been developed in two-dimensions to simulate the structural deformation caused by extension by faulting and pure shear, thermal processes and the flexural isostatic due to tectonic loading. The stratigraphy varies across the region between the block and basins, which has been addressed within the modelling by the development of algorithms to simulate palaeobathymetry, compaction and erosion. Extension within the crust was taken up on multiple faults generating an average total heave of approximately 10-15km. Model results indicate there was non-uniform extension of the lithosphere with greater extension below the fault detachment depth where ductile deformation is the principal deformation mechanism. Results generated using a modelling approach that utilises multiple tectonic events generate stratigraphic patterns of syn-rift and post-rift deposition that support extension at multiple time stages within the Northumberland Trough Region during the early-Carboniferous period. Models that reconcile the observed amount of fault-controlled deformation with the magnitude of overall thinning of the crust generate comparable amounts of subsidence to that observed in the basin structures. In contrast, these models over-estimated the amount of subsidence on the block structures. It has been hypothesised that this mismatch was due to the North Pennines Batholith, which acts as a negative load upon the lithosphere. Development of an algorithm to model the isostatic response of the lithosphere to the North Pennines Batholith has provided insights into the influence of igneous intrusions on the post-emplacement structural development of the area. Model results incorporating the batholith indicate the generation of a significant amount of uplift coincident with the presence of the batholith, and show a realistic geometry and upliftsubsidence pattern across the Alston Block and adjacent basins.

No description available.

Mass movement, fluvial erosion, sediment transport and earthworks - induced instability, often pose major problems for highway design and construction in mountain terrain. This thesis examines the contribution that geomorphological techniques can make to the evaluation of these hazards for highway design purposes in the Lower Himalaya. A review of the consequences of geomorphological hazards to highway stability is illustrated by reference to selected mountain roads in India and Nepal. The design, stability and construction costs of these roads are discussed in respect to their status or function in the road network and, more particularly, the severity of hazards and terrain conditions they encounter. Techniques of hazard and terrain assessment for highway design purposes are examined and tested in the remainder of the thesis. Techniques of medium-scale (1: 10 000-1: 50 000) landslide hazard mapping and large-scale (greater than 1: 10 000) geomorphological ground survey are discussed and tested in the Dharan-Dhankuta area of Nepal, in terms of their ability to provide useful information for alignment design, road stabilization and protection works. The contribution of geomorphological ground survey to highway design is critically assessed by reference to the Dharan-Dhankuta road, and its stability following a high magnitude storm in 1984. A proforma method for assessing flooding, erosion and sediment hazards in small mountain channels is developed. Discharge data for the 1984 storm are derived from these proformas and used to test a number of selected ungauged catchment equations, and to develop empirical relationships between peak discharge and catchment variables for purposes of high magnitude runoff prediction from small catchments. In addition, low-cost, low technology methods for monitoring discharge, slope erosion, sediment transport and mass movement are tested in terms of their ability to provide meaningful data in the short-term for design purposes. Finally, optimum strategies of hazard and terrain assessment for highway design are proposed. The potential for further application of geomorphological techniques and expertise to mountain highway design is discussed.

There has recently been a steady increase in the number of licenses granted for the abstraction of water from the Chalk aquifer beneath London to supply "open loop" geothermal systems (Environment Agency, 2007). However, there has been little research conducted on how the water re-injected by these systems, which often differs in temperature by as much as 10°C, will interact with the fractured Chalk aquifer in both the short and long term. An analytical solution developed by Bodvarsson (1989) was used to show that, for most configurations of a geothermal system, thermal transport would be governed by fractures. It was then proved that the United States Geological Survey SUTRA code could be used to construct a more detailed model of the aquifer. A thermal test was devised to collect hydrogeological and thermal data. This test, along with conventional site investigation techniques, was used at a site in central London. A detailed numerical model of the geothermal system and the aquifer was then constructed in SUTRA. The results showed that the fracture zones found during testing would affect the system performance. Building on these results a procedure was developed for designers, to ensure such systems function in an appropriate way.