The primary aim of this research was to study the relationship between landslide motion and its causes, with reference to large, slow moving, reactivated translational rock slides. The movement of such slides has often been assumed to be uniform over time because poor temporal and spatial monitoring resolutions have not allowed the processes and mechanisms governing the velocity to be identified. The increased spatial and temporal resolution of the monitoring carried out for this research allows these processes to be better understood. Two deep-seated, reactivated translational slides were selected to represent over 7,000 mapped landslides of this type in Tertiary-age sedimentary rocks of New Zealand. Each was closely monitored with an automated network of instruments to detect and measure the effects of rainfall, pore pressure, earthquakes and river stage on changing surface and subsurface movement patterns, with sufficient resolution to link periods of movement to their triggering factors. The dynamics and controls upon these landslides have been investigated by combining multiple interdisciplinary approaches including geology, geomorphology, geotechnics and geomatics. Without such an approach the mechanisms governing their motion could not have been adequately resolved. The deformation behaviour at the two slides during the period of observation would best be described as episodic post-failure creep. The creep patterns observed typically comprised periods of accelerated-, slow- and vertical-creep, punctuated by intervals of rest, which recurred both seasonally and independent of season. Three systems were identified within the recorded unsteady, non-uniform motion: 1) basal sliding; 2) internal plastic deformation and basal sliding; and 3) seasonal surficial shrinkage and swelling unrelated to landsliding. Basal sliding by frictional slip along thin clay seams led to the largest horizontal displacements recorded at both landslides. However, once triggered by pore-pressure increase, accelerated-creep motion by basal sliding did not tend to arrest when basal pore pressure decreased. At both landslides slow horizontal- and vertical-creep occurred together over much of the monitoring period and was related to plastic deformation of the slide mass and basal sliding. This motion occurred at a constant velocity and did not vary with fluctuating pore pressure. Accelerated- and slow-creep motion was regulated by the geometrical complexity of the landslide mass rather than basal pore-pressure-induced increases in shear resistance, or rate-induced increases in material shear resistance.

The dangerous hazard posed by flash flooding to upland communities is likely to increase due to climate change. The flood risk management policy approach has become predominant since the 1990s, with an emphasis on the public awareness of, and responses to, flood risks; however, the unpredictable nature of upland flash flooding means that responses to such hazards are uncertain. This thesis uses an integrated analysis of social and physical science datasets to study responses by local residents and the Environment Agency to flash flooding, using a case study of a major upland flood in North Yorkshire. Responses to flash flooding within upland communities were found to be mostly present as changes to individual behaviour and awareness. However, physical, damage reducing modifications were limited. Flash flood hazard perception was found to be linked to knowledge and experience of local flooding. Major flash flood events occurring in areas which have not experienced other recent floods are unlikely to increase perceptions or provoke responses. Although local awareness of changing weather patterns was found, supporting analyses of rainfall records, local flood risks were frequently framed in the context of river management, rather than climate change. The implementation of policy changes and responses to flash flooding by the Environment Agency will prove difficult at the local level, due to the nature of attitudes and perceptions encountered at the local level, including important differences in the perception of the flash flood hazard between local residents and representatives from nationwide organisations. Encouraging property-level modifications following flash floods, in accordance with national policies, is very difficult. In order to increase local perceptions of the flash flood hazard, the use of participatory work, focusing on long-term awareness raising and the sharing of locally held flood knowledge may be beneficial, alongside the support of existing resilience in upland communities.

No description available.

Debris flows are a major natural hazard in mountains world wide, because of their destructive potential. Prediction of occurrence, magnitude and travel distance is still a scientific challenge, and thus research into the mechanics of debris flows is still needed. Poor understanding of the processes of erosion and deposition are partly responsible for the difficulties in predicting debrisflow magnitude and travel distance. Even less is known about the long-term evolution of debrisflow fans because the sequential effects of debris-flow erosion and deposition in thousands of flows are poorly documented and hence models to simulate debris-flow fans do not exist. Here I address the specific issues of the dynamics of erosion and deposition in single flows and over multiple flows on debris-flow fans by terrain analysis, channel monitoring and fan evolution modeling. I documented erosion and deposition dynamics of debris flows at fan scale using the Illgraben debris-flow fan, Switzerland, as an example. Debris flow activity over the past three millenia in the Illgraben catchment in south-western Switzerland was documented by geomorphic mapping, radiocarbon dating of wood and cosmogenic exposure dating of deposits. In this specific case I also documented the disturbance induced by two rock avalanches in the catchment resulting in distinct patterns of deposition on the fan surface. Implications of human intervention and the significance of autogenic forcing of the fan system are also discussed. Quantification and understanding of erosion and deposition dynamics in debris flows at channel scale hinges on the ability to detect surface change. But change detection is a fundamental task in geomorphology in general. Terrestrial laser scanners are increasingly used for monitoring down to centimeter scale of surface change resulting from a variety of geomorphic processes, as they allow the rapid generation of high resolution digital elevation models. In this thesis procedures were developed to measure surface change in complex topography such as a debris-flow channel. From this data high-resolution digital elevation models were generated. But data from laser scanning contains ambiguous elevation information originating from point cloud matching, surface roughness and erroneous measurments. This affects the ability to detect change, and results in spatially variable uncertainties. I hence developed techniques to visualize and quantify these uncertainties for the specific application of change detection. I demonstrated that use of data filters (e.g. minimum height filter) on laser scanner data introduces systematic bias in change detection. Measurement of debris-flow erosion and deposition in single events was performed at Illgraben, where multiple debris flows are recorded every year. I applied terrestrial laser scanning and flow hydrograph analysis to quantify erosion and deposition in a series of debris flows. Flow depth was identified as an important control on the pattern and magnitude of erosion, whereas deposition is governed more by the geometry of flow margins. The relationship between flow depth and erosion is visible both at the reach scale and at the scale of the entire fan. Maximum flow depth is a function of debris flow front discharge and pre-flow channel cross section geometry, and this dual control gives rise to complex interactions with implications for long-term channel stability, the use of fan stratigraphy for reconstruction of past debris flow regimes, and the predictability of debris flow hazards. Debris-flow fan evolution on time scales of decades up to ten thousands of years is poorly understood because the cumulative effects of erosion and deposition in subsequent events are rarely well documented and suitable numerical models are lacking. Enhancing this understanding is crucial to assess the role of autogenic (internal) and allogenic (external) forcing mechanisms on building debris-flow fans over long time scales. On short time scales understanding fan evolution is important for debris-flow hazard assessment. I propose a 2D reduced-complexity model to assess debris-flow fan evolution. The model is built on a broad range of qualitative and empirical observations on debris-flow behaviour as well as on monitoring data acquired at Illgraben as part of this thesis. I have formulated a framework of rules that govern debris-flow behaviour, and that allows efficient implementation in a numerical simulation. The model is shown to replicate the general behaviour of alluvial fans in nature and in flume experiments. In three applications it is demonstrated how fan evolution modeling may improve understanding of inundation patterns, surface age distribution and surface morphology.

Ice streams drain ice sheets rapidly and are key regulators of their mass balance in both palaeo and contemporary settings. Present day ice streams can be identified, and their short-term activity monitored, by measuring the surface velocity of ice sheets. However, in order to understand their long-term behaviour, reconstructions of their activity in palaeo-ice sheets are necessary. Numerous palaeo-ice streams have been identified in the Laurentide Ice Sheet (LIS) and this has considerably refined our understanding of its dynamic behaviour and links to the ocean-climate system. In the north-west sector of the LIS, ice streaming has been hypothesised but detailed mapping of the area has not been carried out and so our understanding of palaeo-ice streaming is limited compared to other areas. This thesis presents a new ice sheet reconstruction of the north-west sector of the LIS that incorporates ice stream activity and pro-glacial lake evolution. Mapping and analysis was carried out using a range of remote sensing imagery and Digital Elevation Models (DEMs), which enabled widespread, rapid and systematic coverage of the 800,000 km2 study area. More than 95,000 bedforms have been mapped, including glacial lineations, eskers, moraines and palaeo-channels. These data permit the identification and classification of 272 flow-sets which have been dated using an existing 14C database and relative cross-cutting relationships. Flow-sets are used to construct a robust and self-consistent ice sheet reconstruction, incorporating the activity of ice streams at a temporal resolution of up to 250-500 years. The reconstruction reveals major changes in ice sheet configuration during Late Wisconsinan deglaciation and indicates that margin retreat was complex and dominated by the dynamic spatial and temporal evolution of seven ice stream systems. These ice streams were not synchronous but a peak in their activity occurred between 15 and 13 ka. Their location and behaviour was influenced by the availability of soft sediments, but their temporal switching was likely controlled by sub-glacial meltwater routing and ice piracy. Large proglacial lakes developed during deglaciaton but their evolution did not appear to control ice stream activity, as observed elsewhere in the ice sheet. However, major palaeo-channels are consistent with a previously hypothesised north-west drainage route for Glacial Lake Agassiz.

The aim of this thesis has been to improve understanding of the controls on coastal rock cliff erosion, utilising microseismic ground motion. Coastal cliff erosion has remained poorly understood, in part confounded by the challenges associated with monitoring changes to and controls upon steep slopes in the coastal zone. As a result the relative contribution of marine to subaerial and episodic to iterative forcing is based upon models with only limited field validation. For two years, from July 2008 to July 2010, cliff top microseismic ground motions were monitored using a broadband seismometer, installed on top of a 70 m high hard rock cliff of Jurassic mudstone, shale and sandstone, on the North York Moors National Park coast, UK. Concurrently cliff face erosion was monitored using high-resolution 3D terrestrial laser scanning. Regional-scale marine and weather data for the monitoring period and modelled nearshore wave conditions were used to establish the conditions under which cliff microseismic ground motions were generated. Distinct ground motion frequency bands were found to correlate with a range of marine and subaerial processes that transfer energy to the coastline and cliff. Fundamentally, microseismic sources were identified both at the cliff face from, for example, direct wave impact during cliff toe inundation, but also at more distal locations resulting from the transfer of energy from gravity and infragravity waves. Further analysis demonstrates statistically significant correlations between rockfall and cliff ground motion generated by wave impacts and wind at the cliff face, but also surprisingly waves across the nearshore and offshore, implying direct environmental controls on cliff erosion rate. The significance of longer period ground motion, representative of ocean gravity and infragravity waves also identifies an almost constant dynamic loading of the cliff rock mass, highlighting a potential for progressive deterioration of the cliff rock. The analysis demonstrates that cliff top microseismic ground motion provides a valuable proxy for marine and atmospheric forcing at coastal cliffs, overcoming the limitations in quantifying and testing controls on cliff erosion. The findings of this study are used to develop a new conceptual model of the environmental processes and failure mechanisms that control rock cliff erosion.

This thesis is concerned with a study of the glaciation and glacial deposits of a selected part of the South Tyne and Allendale valleys. The results which are presented in this thesis were obtained both from laboratory analyses of the till sediments and from field observations in an attempt to make the study as integrated as possible. The thesis is divided into four sections. The introductory section is a description of the study area in terms of its physical geography and geology. In order to put the present work into context the history of previous glacial research is also outlined. In section two the glacial sediments and landforms are described and the writer's findings are discussed in the light of the previous work. Section three is a sedimentological study of the till deposits and is the only data of its kind yet available for this part of northern England. Section four, the synthesis, is a quantitative and qualitative assessment of the raw data described in the preceding section of this thesis. Two chapters are concerned with a statistical synthesis, while a third is a subjective appraisal of the ice movements of the last glaciation.

Resistance equations developed for pipe flows and open channel flows cannot be applied to model overland flows uncritically. The formulation of these equations employs several assumptions that are specific to the conditions in which they were developed and cannot be universally applied. The hydraulic behaviour of overland flow is distinct from that of pipe and channel flows and can be characterised by a high degree of variability both over space and over time as roughness elements are progressively inundated with increasing depth. A novel methodology of measuring overland flows in the field at a high- resolution permits examination of the interaction between flow variables and surface roughness. Reconstructing the water surface from elevation data and flow extent provides an estimation of the distribution of flow depths and offers a complementary perspective to more conventional approaches. Overland flows are observed to be highly variable both across and between hillslopes. The distribution of flow depths can be modelled using a two-parameter gamma distribution; both parameters show distinct variations with distance downslope and represent the progressive inundation of roughness elements with increasing depth. The flow interacts with soil surface form where it is capable of eroding its bed and the observed slope- independence of rill velocity can be explained by a feedback between flow state (as characterised by the Froude number) and surface roughness. While the existence of this interaction is affected by soil-type, the soil is observed to have little influence on the relationship between surface roughness and overland flow. Resistance is found to be spatially variable; some of this variability could be explained by the classification of areas of similar microtopogiaphy as identified in the field. This classification can be approximated by a thresholded index-based classification and provides a tool for up-scaling to the hillslope scale. Relating roughness to resistance is not straightforward. Complex natural soil surfaces vary in innumerable ways. Traditional roughness measures fall short of providing an adequate description of the complex soil surfaces observed in the field. A variety of alternative measures are developed, each of which captures a different attribute of surface form. These measures are tested to examine their influence on overland flow resistance and a suite of roughness-resistance models is developed which includes the effect of hillslope position to different degrees. Modelled flow resistance can be separated into a constant term and a depth-dependent term and can be easily incorporated into models of hillslope hydrology. This resistance is observed to decline where a hydrological connection, once established, is then maintained. Examination of the concept of hydrological connectivity in a semi-arid context suggests that the interaction between runoff generation and transfer determines not just flood peaks but also total flow amount. It is suggested that flow resistance and hence runoff transfer should be afforded the same detailed consideration as infiltration parameters, i.e. a spatially distributed and variable value (as a function of depth) that can be organised into discrete units akin to those developed for runoff generation. The parameterisation of both infiltration and resistance in this way provides a crucial interaction through the redistribution of soil moisture and runoff over hillslope surfaces. Through this mechanism, the observed complex and nonlinear runoff response to storm events may be explained as these attributes interact with rainfall characteristics and flow network development. Further understanding of this interaction could have practical implications for catchment management and affect the prioritisation of land management decisions.

In this thesis we constrain a three-dimensional thermomechanical model of Greenland ice sheet (GrIS) evolution from the Last Glacial Maximum (LGM, 21 ka BP) to the present-day using, primarily, observations of relative sea level (RSL) as well as field data on past ice extent. The new model (Huy2) fits a majority of the observations and is characterised by a number of key features: (i) the ice sheet had an excess volume (relative to present) of 4.1 m ice-equivalent sea level at the LGM, which increased to reach a maximum value of 4.6 m at 16.5 ka BP; (ii) retreat from the continental shelf was not continuous around the entire margin, as there was a Younger Dryas readvance in some areas. The final episode of marine retreat was rapid and relatively late (c. 12 ka BP), leaving the ice sheet land based by 10 ka BP; (iii) in response to the Holocene Thermal Maximum (HTM) the ice margin retreated behind its present-day position by up to 80 km in the southwest, 20 km in the south and 80 km in a small area of the northeast. As a result of this retreat the modelled ice sheet reaches a minimum extent between 5 and 4 ka BP, which corresponds to a deficit volume (relative to present) of 0.17 m ice-equivalent sea level. The results suggest that remaining discrepancies between the model and the observations are likely associated with non-Greenland ice load, differences between modelled and observed present-day ice elevation around the margin, lateral variations in Earth structure and/or the pattern of ice margin retreat. Predictions of present-day vertical land motion generated using the new Huy2 model are highly sensitive to variations of upper mantle viscosity. Depending on the Earth model adopted, different periods of post-LGM ice loading change dominate the present-day response in particular regions of Greenland. These results will be a useful resource when interpreting existing and future observations of vertical land motion in Greenland. In comparison to the sparse number of GPS observations available, predictions from the Huy2 model are in good agreement to the absolute measurements from south and southwest Greenland. This suggests that the response of the ice sheet to the HTM is reasonably well produced by the Huy2 model and, thus, corroborates our earlier findings. Uplift predictions generated using a surface mass balance reconstruction of the GrIS (Wake et al., 2009), which covers the period 1866-2005, show that decadal-scale ice mass variability over the last c. 140 years plays a small role in determining the present-day viscous response (it is as large as ±0.2 mm/yr). Results from the same reconstruction show that high rates of peripheral thinning in west and southwest Greenland from 1995 to 2005 (due to surface mass balance changes) generate elastic uplift rates over 6 mm/yr. In the final part of the thesis, we examine how non-Greenland ice mass loss influenced vertical land motion and sea-level change around Greenland over the last deglaciation and consider the implications for GrIS evolution. Results from this analysis suggest non-Greenland solid Earth deformation had little impact on the evolution ice sheet. Sea-level change around Greenland which is driven by non-Greenland ice mass loss departs from the associated eustatic signal; largely because of the close proximity of the late North American ice sheets (NAIS). Non-Greenland RSL change is also spatially non-uniform and is characterised by a distinct east-west gradient. For example, we find that from 16 to 14 ka BP rates of sea-level rise remained relatively low in the west (0-2 m/ka), whereas, those in the east reach values between 6 and 8 m/ka (although these results are sensitive to the source of meltwater, in particular, the relative partitioning of meltwater pulse 1A (mwp-1A, 14.2 ka BP) between the North American and Antarctic ice sheets). If the marine breakup of the GrIS was forced by non-Greenland RSL change, then we would expect the retreat of the ice sheet to reflect the sea-level changes described. A preliminary modelling study suggests that, assuming a conventional ice sheet model calving treatment, a more realistic sea-level forcing results in a pattern of ice margin retreat which is at least partly due to spatial variations in non-Greenland RSL change. Thus, the modelled marine retreat is generally earlier in east Greenland and later in the west than for when non-Greenland RSL change is not accounted for - this pattern of ice margin retreat is generally consistent with observations from the continental shelf.

This thesis was carried out to gain a better understanding of the Cenozoic environmental evolution of the San Juan Raya Basin, which is a sub-system of the Tehuacan Valley in central Mexico. The likely roles of tectonics and climate in the geomorphic processes of the basin were examined by analysing the geology, geomorphology, depositional environments, as well as other palaeo-records: palaeosols, fossils and geochemical deposits. The correlation of 11 sedimentary sections was established on the basis of 12 radiocarbon dates. A glyptodont (Xenarthra) fossil discovered as part of this study provided important palaeoenvironmental information. The first hypothesis on the Neogene evolution of the basin is put forward, indicating that this system was formed by NE faults probably since the late Miocene or later. The asymmetry of the alluvial landforms indicates that the main factor controlling the development of Pleistocene fans from the north slope was tectonics. Late Pleistocene-Holocene deposits are more widely spread and represent environmental changes since 28.5 kyr ago. Macrofossil and stable isotopes suggest a mixed vegetation and high evaporative conditions under a poorly drained basin before the Last Glacial Maximum (LGM), probably under a colder than present climate. No records are available between the LGM and the end of the Pleistocene. Higher moisture availability was inferred in the early Holocene on the basis of high deposition rates and in situ tufa, followed by periods of intense deposition during the middle Holocene. A discrete alluvial fan reveals a combination of climate and tectonics. Alluvial incision since 2.3 kyr BP coincides with the establishment of current climatic and geomorphic conditions. Late Quaternary erosion and deposition suggest that climate and tectonics have played a dominant role in controlling the geomorphic processes of this basin.