InSAR was used to remotely prospect for ground deformation and to map lava flows associated with eruptions at Nyamuragira and Nyiragongo volcanoes (DRC). Eleven ERS SAR scenes were obtained. Initial InSAR results revealed excellent interferometric coherence over barren lava surfaces, although coherence was limited over vegetated areas and on the steep upper slopes of the volcanoes. This resulted in isolated patches of coherence, which despite significant modifications to the processing technique, could not be bridged during the unwrapping of the interferograms. However, reliable results were achieved by processing the isolated areas separately. New areas of interferometric coherence enabled lava flows emplaced during the 2002 Nyiragongo, and 1998 and 2001 Nyamuragira eruptions to be identified and mapped in higher detail than was available in existing maps. Based on the mapped flow areas and assumed flow thicknesses, minimum estimates for the erupted volumes were found to be 22 x 10⁶ m³, 71 x 10⁶ m³ and 133 x 10⁶ m³, respectively. Previously undetected deformation signals were found over both long (years) and short (weeks) time-periods. A persistent and generally decreasing subsidence was observed in Nyamuragira’s NE flow field, and was attributed to post-emplacement cooling and densification of pre- 1997 lavas and associated substrate relaxation due to lava loading. Localised inflation and deflation signals were observed on Nyamuragira’s NE flanks and summit caldera, and were interpreted as reflecting the dynamics of shallow magma systems. Maximum deformation rates within Nyamuragira’s summit caldera were about five times greater than those recorded for the NE flanks. Inflation of Nyamuragira’s NW flanks was interpreted as being due to magma accumulation prior to the 2002 eruption.

In order to determine the effect of aquatic macrophytes on channel hydrology, a model was developed to calculate channel resistance for rivers containing vegetation growth. Separate models of grain resistance and vegetation resistance were developed, which can then be combined to estimate the total resistance. The grain resistance model uses a measure of the size of grains on the channel bed. The choice of which grain size percentile to use, for such a model, is founded on both theoretical and empirical assessments of the precision of sampling different percentiles. Studies are presented, which demonstrate the complexity of the velocity distribution in the vicinity of aquatic plants; a distribution which is dependent on the types of plant present. These findings are used to identify the major ways in which in-channel vegetation affects channel resistance, for use in the vegetation resistance model. Consequently, this model uses the blockage factor, which is the proportion of the channel that is occupied by vegetation. This is a measure of the volume displacement effect of the vegetation, in acknowledgement that most of the flow is displaced from within a plant body. The model also includes a measure of the relative length of the vegetation boundary to that of the channel's wetted perimeter, since this factor controls the resistance to the flow between the vegetation stands. The effectiveness of this model is compared against other vegetation resistance studies, while the possibility of developing a predictive model which calculates channel resistance under different hydraulic conditions is also discussed. The results of these models are then used to assess if aquatic macrophytes significantly contribute to flooding, and to consider whether it is necessary to manage these channels. New management techniques are also proposed based on the findings of the models developed in this thesis.

The study outlines the glacimarine sedimentation patterns and processes and environments in the Kejser Franz Josephs Fjord and on the adjacent continental margin of East Greenland during the Late Weichselian and Holocene. A variety of techniques are adopted in the study in order to address the objectives outlined previously. The study is based on a suite of 8 cores from the mid to outer region of Kejser Franze Josephs Fjord, and the continental shelf and slope. Core analyses included i) logging (core and x-radiographs), ii) determination of grain size distribution, iceberg rafted debris and physical properties (water content, porosity, grain density), iii) determination of stable oxygen and carbon isotopes, iv) radiocarbon dating, and v) calculation of sedimentation and accumulation rates. Additionally, acoustic data is incorporated into the study to place the sediment cores within a regional context in terms of the sedimentation patterns and processes throughout the study area. The sedimentary record within the study dates back to the Late Weicheselian glaciation. The sedimentary record corresponding to the Late Weicheselian glaciation is confined to the continental slope, and partly the continental shelf. The nature, timing, extent and mechanisms of ice advance during the Late Weichselian glaciation could not be determined in the study. The upper continental slope is characterised by iceberg sedimentation with additional contribution from distal remnants of meltwater outflows escaping from East Greenland, sea ice rafting and pelagic settling. Mass wasting is recognised by the presence of debris flows, which are derived from the rapid and unstable build-up of large volumes of glacigenic sediment. Mass wasting events are intermittent, vary from small to large scale, and are derived from local slope regions. The mid to lower continental slope are characterised by rain out and suspension settling punctuated by intermittent sediment gravity flows. Sea ice conditions during the Late Weichselian are extended resulting in reduced ventilation of ocean surface waters and decreased exchange of CO<SUB>2</SUB> between the atmosphere and ocean. Sedimentation rates are high in relation to sedimentation being focused onto the continental margin as ice advances to the inner continental shelf.

This study aimed to develop and evaluate a numerical simulation model of the interdependent dynamics of channel form, processes and floodplain vegetation using cellular automaton approaches. The model was developed and evaluated using data from the River Feshie, Scotland. Firstly, field and historic data were examined in order to understand the ecology and dynamic nature of the study site. The braidplain was shown to exhibit a number of different mechanisms of change, varying from a wandering anabranch river to a more fragmented braided pattern; however the relationship between channel pattern and vegetation was not found to be straightforward, and multiple successional pathways were identified, depending on local abiotic conditions. Secondly, the capability of cellular automata models to simulate realistic patterns of discharge, channel change and floodplain ecology was evaluated. Cellular automata models involve a high level of simplification in order to facilitate the modelling of medium time and space scales with highly mobile boundary conditions. The models can predict realistic patterns of discharge and reach-scale ecology compositions, but further work is needed to improve the sediment transport functions. Finally, a cellular automata model was applied to investigate how floodplain ecology responds to different flood disturbance regimes and land management practices. This showed that cellular automata models may be used successfully to explore relationships between discharge, land use management and floodplain ecology. However, uncertainties regarding the lack of physical realism in some aspects of the model predictions meant it was unclear to what extent the results accurately represented future conditions for the River Feshie. Therefore, at this stage cellular automata models cannot be recommended for detailed applied management purposes in specific contexts.

No description available.

No description available.

The aim of this thesis is to quantify controls on erosion rates in the Taiwan mountain belt across a range of time-scales. Erosion rates in the Taiwan orogen are estimated from modern river sediment loads. Holocene river incision rates, and the thermochronometry on a million-year time-scale. Erosion rates within the actively deforming mountains are high (3-6 mm yr^-1) on all time-scales, but the pattern of erosion has changed over time in response to the migration of localized tectonic deformation. Modern, decadal erosion rates correlate with historical seismicity and storm-driven runoff variability. The highest erosion rates are found where rapid deformation, high storm frequency and weak substrates coincide, despite low topographic relief. The geomorphic impact of individual earthquakes and typhoons is analysed through the natural experiment provided by the 1999 <i>M</i>_w 7.6 Chi-Chi earthquake and subsequent typhoon storms. Following the Chi-Chi earthquake, a 2-4-fold increase in sediment concentration was observed in rivers draining the epicentre region. Sediment was transferred from hillslopes to rivers in a cascade of processes. The earthquake triggered widespread landsliding on hillcrests and left large amounts of debris stored on hillslopes. Subsequent typhoons reworked this material and triggered new landslides in bedrock that had been weakened by co-seismic ground motion. Rivers draining the Taiwan mountain belt delivered 384 Mt yr^-1 of suspended sediment to the ocean between 1970-1998. This amount represents 1.9% of estimated global suspended sediment discharge, yet is derived from only 0.024% of the Earth’s subaerial surface. Much of this sediment (30-42%) is delivered in hyperpycnal river plumes that sink to the sea-bed and may deposit turbidites. The rate of turbidite deposition increased by approximately 4 times following the Chi-Chi earthquake.

This study explores field and numerically modelled datasets on wave and wave-driven processes within the macro-tidal Blackwater Estuary in Essex, U.K. The wave climate of the Blackwater Estuary was characterised from wave records collected from 1994 to 1996 at 5 monitoring stations within the estuary. From these records and hindcasted offshore wave records over this period, locally-generated wind waves, wind-sea, and swell waves were identified and their significance assessed in terms of probability of occurrence and variability in different sections of the estuary. The Blackwater Estuary is found to be subject to waves from both offshore and from within the estuary, with evidence of seasonality within these wave climates. Longer-term wave and tidal height distributions were predicted through a Weibull probability model and their joint probability established for different return intervals. A numerical wave model (MWAVE_REG) was used to quantify the temporal and spatial impact of a variety of hydrodynamic scenarios (including 'worst case') within the Blackwater Estuary. The effects of wave diffraction, reflection and refraction were evaluated and areas of wave focusing within the estuary identified. The model was subsequently used to predict morphological changes per 1km shoreline, linking modelled hydrodynamics to observed morphological changes. The significance of the distribution of wave energy within the estuary for sediment entrainment, transport and deposition is discussed. In order to modify the highly artificial estuarine system of the Blackwater, a number of potential managed realignment sites were identified. From the hydrodynamic and morphodynamic findings of this study; these may aid in the reaction of a more natural estuarine system, better able to absorb extreme water local events.

This thesis describes the development, testing and use of a distributed, physically based model of snow melt and runoff for alpine glaciers. A distributed version of a one-dimensional energy and mass balance snowpack model, SNTHERM, is coupled to a two-dimensional saturated flow model, MODFLOW, and is used to simulate meltwater production, vertical and lateral routing, storage and runoff across the temperate Haut Glacier d’Arolla, Switzerland at the beginning of the 2000 melt season. SNTHERM was first modified to incorporate an albedo scheme parameterised for this glacier, and to stimulate melt and runoff from glacier ice in additional to the seasonal snowpack. The performance of this 1-D model was tested against a suite of observations made on the glacier during spring 2000. It was found to reproduce observed rates of snowpack ablation and unsaturated meltwater movement through the snowpack well. The model was then used to investigate the relative contribution of the surface energy balance components to surface melt, and the delay in runoff and short-term storage of meltwater caused by unsaturated flow. A distributed version of SNTHERM was developed for use across the glacier. A digital elevation model (DEM) of the glacier surface and surrounding topography, together with data from a weather station located on the glacier, were used to calculate input variables of slope angle, aspect, shading and meteorological conditions across the glacier surface on a grid with a spatial resolution of 50 m. Initial snowpack depths and densities at the start of melt were determined from a snow survey conducted around the time of peak accumulation, with snow depth measurements interpolated onto a grid with the same resolution as the meteorological variables. SNTHERM was then run for each grid cell at an hourly resolution. Model performance was shown to be good when tested against repeat measurements of snow depth and albedo made along a glacier centreline stake network.

No description available.