An integrated novel, two-dimensional, numerical groundwater-surface flow model has been developed to simulate hydro-environmental interactions between wetland areas, the neighbouring coastal waters and the groundwater passages. The main target in this research was to prepare a general linked model, which could be applied to different applications. For free surface flow modelling, an existing widely used two-dimensional, unsteady mathematical model, named the DIVAST model (Depth Integrated Velocities And Solute Transport model, developed originally by Falconer 1976) has been refined. However, in order to simulate the flow and solute transport in porous media, a two-dimensional model namely the GWK (Ground Water Key) has been developed to include an aquifer influenced by tidal currents. The GWK model is based on the transient flow Boussinesq equation as the governing equation for groundwater flow, and the advection-diffusion equation is used as the governing equation for contaminant transport. The model predicts the water table, the velocity components in the horizontal plane, the recharge/discharge levels for source/sink on the water table and solute tracer levels across the domain. The finite difference scheme used in this model is based upon the Alternating Direction Implicit (ADI) technique and using orthogonal grids. The structure of the GWK model is based on having a good relationship with the free surface flow model. The two sub-models (DIVAST-GWK) are linked by an interface, and flow and pollutants are able to pass across the interface in both directions, depending on the relative height of the water levels. A physical scale model has been constructed to provide experimental data of the groundwater transport between an idealised wetland and the adjacent coastal waters. However, in the dimensional analysis and designing of the physical model the Fleet Lagoon and adjacent coastal waters, in Dorset just west of Weymouth and the Isle of Portland UK, was chosen as a typical prototype. In the physical model the aim has been to study seepage behavior through the sand embankment by recording water levels on both sides of the sand, point velocity measurements, and the studies of a conservative dye tracer for constant water levels on one side of the embankment while running tidal cycle on the other side of the sand ridge. The integrated model has been verified using the laboratory data. Comparison between the experimental data and the simulated physical model, involving numerical linked model, showed that the integrated model was capable of simulating both phenomena, groundwater and free surface water, with a high level of accuracy.

Morphology and movements of sand dunes are studied using repeated high-resolution bathymetric data in areas where banner banks approach the shore. Two sites in the Bristol Channel were selected for their contrasting environments. The Helwick Sands is characterised by deeper water-depths, stronger wave climates and weaker tidal currents than the Nash Sands. At the Helwick, migrations of the dunes were measured ranging between 21 and 109 hlv"1. Dunes crossing its crest and connecting despite opposite direction of migration on either flank were observed. This geometry is interpreted to be the result of the strong wave climate coupled with a nearly rectilinear tidal flow, which are leading to dune crests extension. A morphometric study of the sand dunes has revealed the tendency for the dunes to flatten in shallow water, which can also be attributed to the effect of the waves. At the Nash, strong currents and breaking waves have created a strong crestal escarpment. Dune migration rates along the flanks were measured to range from 34 to 180 m.y"1 {Text not available}, based on a comparison of surveys 263 days apart. However, in the Nash Passage (between East Nash and the coast) short term (19 days) sand dunes migration measurements revealed very fast moving (up to 715 m.y_1) small short-living sand dunes. Celerity and morphology of the dunes were used to compute sand transport specific fluxes. Such fluxes are broadly compatible with fluxes computed from tidal current data using bedload transport formulae. For both banks, the geometry of the flux vector field suggests a clockwise sand transport pattern around the banks. Although different intensities of the fluxes were expected at the two sites, the fluxes of corresponding morphological areas are similar. Differences in the tidal current asymmetry and reduced effective threshold of sand transport due to the wave energy are invoked to explain theses similarities. Pattern of erosion and deposition were evaluated from the divergence of sand fluxes. This partem has revealed the occurrence of transients in the sand transport, which are the result of complex interactions between the flow, the headland and the bed morphology.

The aim of this project is to improve our understanding of the past European and British ice sheets as a basis for forecasting their future. The behaviour of these ice sheets is investigated by simulating them using a numerical model and comparing model results with geological data including relative sea–level change data. In order to achieve this aim, a coupled ice sheet/lithosphere model is developed. Ice sheets form an integral part of the Earth system. They affect the planet’s albedo, atmospheric and oceanic circulation patterns, topography, and global and local sea–level change. In order to understand how these systems work, it is necessary to understand how ice sheets interact with other parts of the climate system. This project does this by simulating ice behaviour as part of the climate system and evaluating model behaviour in relation to evidence of past ice sheets. Ice sheet simulations can be treated with more confidence if they can be evaluated against independent data. A methodology is therefore developed that compares relative sea–level records with simulations of past sea–level which result from modelling past ice sheets with a dynamic, high–resolution thermo– mechanical ice sheet model coupled to an isostatic adjustment model. The Earth’s response to changing surface loads is simulated using both a regional, flat Earth approximation and a global, spherical self–gravitating Earth model. The coupled model is tested by initially simulating the past Fennoscandian ice sheet because of the simpler topographic framework and the quality of geological evidence of past fluctuations against which to evaluate model behaviour. The model is driven by a climatic forcing function determined so that the simulated ice sheet resembles the past Fennoscandian ice sheet as reconstructed from geomorphological evidence. The Fennoscandian climate driver is then transferred to the British Isles to simulate the past British ice sheet. Finally, a non–linear regression technique is used to construct future ice sheet drivers from future sea– level change scenarios to forecast sea–level change around the British Isles during the next glacial cycle. The data used for the inversion procedure is limited to southern Scandinavia. Outside this area, the simulation compares poorly with reconstructions based on geological observations. However, model fit within this region is good and the simulation is also in good agreement with features not used during the inversion process. This approach illustrates the benefit of using a model coupling realistic ice physics to a realistic Earth model to help constrain simultaneously unknowns of Earth rheology and ice thickness. Ultimately, relative sea–level data together with other strands of data, such as geomorphological evidence, and a coupled ice sheet/isostatic rebound model can be used to help infer past climates.

No description available.

The central sector (NW England and Scottish borders) of the last British-Irish Ice Sheet exhibits a palimpsest glacial geological and geomorphological signature characteristic of multi-phase ice flow and ice-marginal fluctuations. Despite its influential position at the heart of the British-Irish Ice Sheet, sourced from major ice dispersal centres of the northern Pennines, Lake District and Southern Uplands, and drained via fast-flowing outlets such as the Irish Sea Ice Stream, the region remains poorly constrained, both temporally and in terms of ice-flow dynamics. The principle goal of this thesis was therefore to reconstruct the palaeoglaciology of the central sector of the British-Irish Ice Sheet during the last glacial cycle, focusing on: (1) ice-flow dynamics with respect to palaeo-ice divides, ice-dispersal centres, flow trajectories and flow phasing; (2) the relative chronology of ice flows during advance and decay of the ice sheet; and (3) evidence for ice stream activity either within or sourced from the study area. The thesis adopted a dual approach involving both geomorphological mapping and sedimentological analysis. A 5 m resolution NEXTMap DEM was used to map over 9,000 individual landforms including subglacial lineations, hummocky terrain, moraines, meltwater channels, eskers and glaciofluvial sediment accumulations. Subglacial lineations were subdivided into discrete flow sets demarcating distinctive flow phases, and a relative chronology produced from cross-cutting relationships. Thirteen field sites, concentrated in the Solway Lowlands, supported by data collected from over 200 boreholes enabled detailed stratigraphic and sedimentological analysis to be carried out. This included stratigraphic logging, the collection of macrofabrics, particle size and geochemistry analysis on till matrixes, clast lithological counts, varve analysis and microstructural (thin sections) data. Results from this study have demonstrated that the central sector of the ice sheet was characterised by repeated ice-flow switches, initiation and termination of ice streams, drawdown into ice streams, repeated ice-marginal fluctuations (the Scottish and Blackhall Wood Re-advances) and the production of large volumes of meltwater, often impounded to form ice-dammed lakes. Six main stages of ice flow have been recognised in the region, of which stage I is thought to indicate the period of maximum ice expansion, while stages II-VI record the deglacial history. A pre-stage I event is also discussed and can be reconciled with the initial expansion of ice out of upland dispersal centres. Stage I was characterised by ice flowing eastwards across the country through major topographic lows of the Stainmore and Tyne gaps. The Tyne Gap was occupied by a topographic ice stream, which was heavily influenced by the changing dominances of both Lake District and Southern Upland ice-dispersal centres. Migration of ice divides back towards upland dispersal centres during stage II resulted in the flow of ice through the Stainmore Gap being cut-off, while the northern edge of the Tyne Gap ice stream was breached by a SE ice flow down the N Tyne Valley. Despite the maintenance of the Irish Sea Ice Stream off the western coast of Cumbria throughout stage III, the Tyne Gap and Solway Lowlands underwent widespread deglaciation. Meltwater from the Tyne Gap was routed into Glacial-Lake Wear via a major proglacial drainage network in the South Tyne Valley, while the natural basin of the Solway Lowlands also ponded-up (Glacial-Lake Blackhall Wood) as drainage became impeded by the Irish Sea Ice Stream. The overall pattern of retreat was reversed during the Blackhall Wood Re-advance (stage IV), during which ice was vigorously drawn down into the Irish Sea Ice Stream. Stage V was characterised by the continued retreat of ice out of the central sector of the British-Irish Ice Sheet; with the vast amounts of meltwater generated impounded in ice-marginal lake systems (Glacial-Lake Carlisle), or routed through meltwater channel networks or evolving glacier karst (Brampton kame belt). The landforms of the Brampton kame belt can be reconciled with ice stagnation on the reverse slope of the Tyne Gap, and is thought to have formed one component of a much larger, time-transgressive drainage network involving the Pennine escarpment and Tyne Gap meltwater channel systems. The final recognised stage in the glacial history of the region was the Scottish Re-advance, a brief incursion of ice, sourced from the Southern Uplands, onto the fringe of the Solway Lowlands. A large glacial lake is identified to have formed at the ice front, dammed against ice in the Irish Sea basin and delimited by a large deltaic complex at Holme St. Cuthbert.

No description available.

Estimating groundwater recharge to aquifer systems is a very important element in assessing the water resources of the West Bank. Of particular interest is the sustainable yield of the aquifers. Previous studies have developed analytical recharge models that are based on the long-term annual rainfall data. These models have been shown to be inadequate and changes over shorter periods, e.g. monthly estimates, must be known in order to study the temporal distribution of recharge. The approach used in this research integrates data derived from satellite images (e.g. land cover, evapotranspiration, rainfall, and digital elevation model) with hydrogeological data in a Geographic Information System (GIS) model to identify and map the surface recharge areas. The Surface Energy Balance Algorithm for Land (SEBAL) is applied to time series of remote sensing MODerate Resolution Imaging Spectroradiometer (MODIS) level 3 data of reflectance and surface temperature measurements to estimate monthly evapotranspiration; precipitation is derived from the monthly data sets of the Tropical Rainfall Measuring Mission (TRMM); runoff is given assumed values of 0.75 mm month-1 and 0.4 mm month-1 for the months of January and February, respectively. Recharge is quantified from November until March by applying the water balance method where evapotranspiration estimates and runoff are subtracted from precipitation. Results show good agreement between data reported in the literature and remote sensing-based analysis. Empirical models that are based on long term rainfall measurements suggest recharge values between 800 and 836 MCM yr-1 while the remote sensing based model results estimate recharge to be 700 MCM yr-1. The Western, North-Eastern, and Eastern Aquifer Basins receive 30%, 23%, and 47% of the total calculated recharge while percentages available in the literature provide 49%, 22%, and 29%, respectively. Discrepancies are mainly due to lack of field data, the overestimation of actual evapotranspiration, and underestimation of TRMM precipitation values. The recharge map indicates that the most effective groundwater recharge zones are located in the north and west of the area that is characterised by thick and well developed soil deposits, heavy vegetation, and a sub-humid climate with the potential of significant recharge occurring during the wet season. Some areas in the east include concentration of drainage and stream flows which increase the ability of to recharge the groundwater system. The least effective areas are in the south and south-west region that is more arid with much less recharge, mainly due to its isolated thin soil deposits. A sensitivity analysis was carried out to demonstrate the impact of land cover change on groundwater and natural recharge. The assessment involved the use of land covers of 1994 and 2004 with the same fixed parameters of evapotranspiration, precipitation, drainage, slope, soil, and geology. Results show a decrease in high and intermediate high recharge areas from 40.25 km2 and 2462.25 km2 in year 1994 to 15.5 km2 and 1994 km2 in 2004, respectively. This illustrates the extent of land cover/land use change influence on recharge and calls for integrated plans and strategies to preserve recharge at least at its current rates.

No description available.

Using observations of land surface deformation, sea level change and geophysical modelling, this thesis considers the interactions of ice mass fluctuations and tectonic deformation over the last great earthquake cycle in south central Alaska. Reconstructions of relative sea level change over the last 900 years, based upon extensive lithological, biostratigraphical and chronological investigations of salt marsh sequences in upper Cook Inlet, Alaska, record changes in marine influence and the direction of sea level that do not fit the expected interseismic model of land level movements. Dating of the sequences suggests the changes in RSL occurred sometime through c. AD 1600 – 1900, during the middle and late phases of Little Ice Age ice mass balance changes. The chronological methods used comprise a multi-method approach: 210Pb, 137Cs, stable lead (206Pb/207Pb) ratios, pollutants associated with the history of regional gold mining and development, tephrochronology and AMS 14C wiggle match dating. The research highlights some of the limitations of applying some of these dating methodologies to recent, high latitude, salt marshes. GIA modelling identifies part of the GPS measured present day uplift in upper Cook Inlet as attributable to post Little Ice Age (AD 1200 – 1900) glacial isostatic adjustment, with a spatial signal over tens of kilometres. A set of viable Earth models, constrained by GPS data and the pattern of post-seismic displacement quantifies the relative displacement and deformation of the ocean geoid at a series of locations in south central Alaska over the past 1000 years. Modelling results show the asthenosphere viscosity and thickness to be the main rheological controls on relative displacement during the last earthquake deformation cycle. Integration of the geological data and geophysical model results show RSL in upper Cook Inlet during the last earthquake deformation cycle is a combination of tectonic land-level changes, ‘local’ processes, glacial isostatic adjustment and deformation of the ocean geoid. To fully quantify the relative contribution of each mechanism requires improvements in the methods of RSL reconstruction, dating of recent salt marsh sediments and GIA modelling.

This thesis examines the relationship between rural land management and downstream flood risk. The recent increase in flood frequency and magnitude has been hypothesised to have been caused by either climate change or land management. The theoretical basis for why these factors might increase flood risk is well known, but showing their impact on downstream flood risk remains a challenge. Field scale studies have found that changing land management practices does affect local runoff and streamflow. Upscaling these effects to the catchment scale continues to be problematic,both conceptually and, more importantly, methodologically. Conceptually, upscaling is critical. As land management may impact upon the relative timing as well as the magnitude of runoff, any changes in land management practice may lead to changes in the synchronisation of tributaries flows, either reducing or increasing downstream flood risk. Methodologically, understanding this effect requires capturing the spatial resolution associated with field-scale hydrological processes simultaneously with the upscaling of these processes to the downstream locations where flood risk is of concern. Most approaches to this problem aim to upscale from individual grid cells to whole catchments, something that restricts the complexity of possible process representation,produces models that may not be parsimonious with the data needed to calibrate them and, faced with data uncertainties, provides computational limitations on the extent to which model uncertainty can be fully explored. Rather than upscaling to problems of concern, this thesis seeks to downscale from locations of known flood risk, as a means of identifying where land use management changes might be beneficial and then uses numerical modelling to identify the kinds of management changes required in those downscaled locations. Thus, the aim of this thesis is to test an approach to understanding the impacts of rural land management upon flood risk based upon catchment-to-source downscaling. This thesis uses the case study of the River Eden catchment (2400 km2) as a test case. Firstly the downstream flood risk problem was assessed using both gauged data and documentary evidence to investigate the historical flood record. This found the last decade does not differ significantly from previous flood rich periods, which were defined as 1) 1873-1904; 2) 1923-1933; and 3) 1994-present. Second, the potential causes of floods within the catchment were investigated; firstly climate variability was assessed using Lamb weather types, which found that five weather types were responsible for causing 90% of the floods in the last 30 years. Third, spatial downscaling of catchment-scale flood risk was undertaken using two methods; databased statistical analysis; and hydraulic modelling. Both approaches consider the magnitudes and the timing of the flows from each major sub-catchment. The statistical approach involved a principal components analysis to simplify the complex subcatchment interactions and a stepwise regression to predict downstream flood risk. The hydraulic modelling approach used iSIS-Flow to undertake a series of numerical experiments, where the input hydrographs from each tributary were shifted individually and the effect on downstream peak stage assessed. Both these approaches found that the Upper Eden and Eamont sub-catchments were the most important in explaining downstream flood risk. The Eamont sub-catchment was chosen for future analysis as:(1) it was shown to have a significant impact on downstream flood risk; and (2) it had range of data and information needed for modelling land use changes. The second part of this thesis explored the land management scenarios that could be used to reduce flood risk at the catchment scale. The scenarios to be tested were determined through a stakeholder participation approach, whereby workshops were held to brainstorm and prioritise land management options, and then to identify specific locations within the Eamont sub-catchment where they could tested. There were two main types of land management scenarios chosen: (1) landscape-scale changes,including afforestation and compaction; and (2) channel modification and floodplain storage scenarios, including flood bank removal and wet woodland creation. The hydrological model CRUM3 was used to test the catchment scale land use changes,while the hydraulic model iSIS-Flow was used to test the channel and floodplain scenarios. It was found that through changing the whole of a small sub-catchment(Dacre Beck), the scenarios of reducing compaction and arabilisation could reduce catchment scale (2400 km2) flood risk by up to 3.5% for a 1 in 175 year flood event(January 2005). Changing localised floodplain roughness reduced sub-catchment (Lowther) peak stage by up to 0.134 m. This impact diminished to hardly any effect on peak flow magnitudes at the sub-catchment scale (Eamont). However, these scenarios caused a delay of the flood peak by up to 5 hours at the sub-catchment scale, which has been found to reduce peak stage at Carlisle by between 0.167 m to 0.232 m, corresponding to a 5.8% decrease in peak discharge. A key conclusion is that land management practices have been shown to have an effect on catchment scale flooding, even for extreme flood events. However, the effect of land management scenarios are both spatially and temporally dependent i.e. the same land management practice has different effects depending on where it is implemented, and when implemented in the same location has different effects on different flood events.