No description available.

No description available.

Rivers discharge around 20 billion tonnes of sediment to the coastal ocean each year (Milliman and Syvitski, 1992). Many supply dominated rivers possess large subareal and subaqueous deltas, whose growth depends on the physical processes controlling sediment deposition or removal. There has yet to be a complete understanding of how short term processes such as settling from buoyant plumes, wave/current resuspension, and transport by currents and gravity flows, interact to produce the depositional products that develop over varying timescales. The Po River in Northern Italy forms a substantial delta in the Adriatic Sea. It has five distributary mouths, and is responsible for a third of all freshwater and sediment entering the Adriatic. Near-field sediment transport is influenced predominantly by Po River floods and two dominant wind regimes. Cold, dry Bora winds blow from the northeast, while warm, wet Siroccos blow from the southeast. Both of these winds produce waves large enough to resuspend sediments off of the Po delta. A three-dimensional numerical modeling study was conducted using the Regional Ocean Modeling System (ROMS) examining sediment transport near the Po delta. ROMS includes sediment settling, wave/current resuspension and transport, and multiple grain types. Simulations and idealized test cases were run. The simulation spanned September, 2002 – March, 2003, and included a large flood event. The idealized cases examined distinct Bora and Sirocco events. Meteorological forcing was based on realistic wind and wave fields. Fluvial sediment was modeled using both flocculated and unflocculated sediment types. A stretched grid with ~750m resolution over the Po delta was used. Compared to earlier models, this increases resolution at the delta and more accurately resolves near-field sediment dynamics. This study indicates that high initial settling significantly reduces the influence of buoyant plume transport on sediment fluxes. Most sediment flux, and export from the delta, occurs within a few meters of the seabed, and is driven by the wave action and near-bed currents generated during wind events. Time-averaged currents dictate the direction of net sediment flux. Under idealized conditions Sirocco winds transport sediment predominantly southward, while under Bora winds relatively more sediment is transported east, and northeast, of the delta. Time-variation in the simulation conditions, however, generates significant southward fluxes during more realistic Bora conditions. Most sediment is deposited directly off the river mouths, with the remaining depositional patterns dictated by current flow and bed shear stress patterns during wind events. The footprint and total sediment mass of the 2002 flood deposit is reasonably well represented, taking limitations of the observational sampling methods into account, specifically, by limiting the model’s predicted deposit to that >5mm thick and within water depths >10m. Predicted maximum depositional thicknesses, however, are ~2-5 times those observed. Fluvial sediment deposition predicted for typical meteorological conditions is consistent with accumulation patterns that develop over much longer timescales. The long-term depositional patterns off the Po delta are similar to those produced by Bora winds, implying that the ~100 year accumulation pattern on the Po delta may be predicted through the modeling of idealized Bora events.

Doctor of Philosophy / Department of Geography / Melinda Daniels / Great Plains rivers are unique systems that vary from large, continental scale, to small intermittent streams with grain sizes that range from bedrock to cobbles to silt. These rivers have been subject to widespread hydrologic alteration both within the channel and the watershed, which has resulted in an alteration in their hydrologic and geomorphic regimes. Although there is an acknowledgement of this alteration, to date there has not been a synthesis of the hydrology of Great Plains rivers or of their longitudinal morphologies. Chapters in this dissertation provide, to my knowledge, the first comprehensive analyses of the hydrology and morphology of Great Plains rivers over a range of spatial and temporal scales. In the first study, I found that there was no uniform pattern of hydrologic alteration throughout the Great Plains, which is likely attributable to variable system-specific reservoir management objectives, land use changes, and climatic regimes over the large area the Great Plains encompass. Results of this study are the first to quantify the widespread hydrologic alteration of Great Plains rivers following impoundment. In the second study, I found an apparent decoupling between local moisture conditions and streamflow in intermittent prairie streams. Results of this study used statistical models to identify relationships between flow intermittence, mean annual flow, and flood flow characteristics with moisture to characterize flow in an intermittent prairie stream. In the final study, I found that the downstream trends in hydraulic geometry and substrate characteristics of the Ninnescah River were consistent with the expected trends proposed by hydraulic geometry and substrate theories. However, there were points that deviated from the expected trends, most notably where a substantially large tributary enters the Ninnescah River and as the Ninnescah River approaches the Arkansas River, and causal explanations for these deviations were explored. Results of this study are, to my knowledge, the first of its kind to assess the longitudinal hydraulic geometry and substrate characteristics of a large sand-bed river over a large spatial scale. To our knowledge, there have been no comparable studies exist that attempted to describe hydrologic and geomorphic characteristics of prairie streams.

Esta pesquisa apresenta um retrato da dispersão urbana que ocorre na região da Macrometrópole de São Paulo sobre a ótica da apropriação do relevo. Quais são os compartimentos de relevo que estão sendo ocupados pelas peças urbanas que se dispersam sobre a área anteriormente utilizada pelos usos relativos ao mundo rural, e em que medida essas peças urbanas residenciais, industriais ou mistas, diferem da morfologia de suas congêneres da cidade compacta, e as consequências ambientais decorrentes dessa forma de apropriação. A partir de uma proposta metodológica de abordagem estratégica do relevo na escala regional, e tendo como base categorias de análise da geomorfologia, este trabalho identifica no processo de dispersão, além de uma tendência de ocupação indiscriminada, e sem critérios ambientalmente claros, de todos os tipos de compartimento de relevo, inclusive daqueles que se pode considerar como compartimentos ambientais estruturantes da paisagem regional para a regulação dos processos naturais e de sua ocorrência não conflituosa com os usos urbanos. Essa ocupação dispersa, que impacta esses compartimentos ambientais estruturantes, é realizada tanto pelas camadas de alta e de baixa renda, como também pelos usos industriais e de comércio atacadista, embora esses grupos apresentem predominância em vetores de dispersão diferentes. / This research presents a portrait of the urban sprawl that occurs in the large metropolitan area of São Paulo, in view of the allocation of relief. Which relief sectors are occupied by urban works that disperse over the region formerly used by the rural area, and to what extent these residential, industrial or mixed urban works differ from the morphology of its equivalents in a compact city, and the environmental consequences resulting from this form of allocation. From a methodological proposal for a strategic approach to relief on a regional scale, and based on analytical categories of geomorphology, this paper identifies the dispersion process and a trend of indiscriminate occupation, without clear environmental criteria, of all types of relief sectors, including those that can be considered as environmental zones of regional landscape designated for the regulation of natural processes and their occurrence without conflict with urban uses. This dispersed occupation, which impacts these environmental zones is performed by both levels of high and low income, but also by industrial uses and wholesale trade, although these groups predominate in different dispersal vectors.

by Lo Chuk-ching. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985 / Bibliography: leaves 92-96

Much of the pioneering work on caves of the Cumberland Plateau (province spanning Tennessee, Kentucky, Alabama, and Georgia) has been stratigraphically located within the Mississippian Bangor and Monteagle Limestones, wherein some of the region’s largest and most spectacular caves occur. Of interest to the understanding of this karst landscape, but severely underrepresented in the literature thereof, are caves and karst features in a heterogeneous sequence of clastics and carbonates known collectively as the Pennington Formation (Upper Mississippian). This work consisted of a regional study of Pennington caves on the western Cumberland Plateau escarpment (Alabama and Tennessee), and a case study of Pennington caves in Savage Gulf State Natural Area (Grundy County, Tennessee). The objective of this research was to determine controls on speleogenesis in the Pennington Formation, using cave geomorphology, dye tracing, and GIS to explore lithologic, hydrologic, and structural influences on karst processes. This resulted in a conceptual model for speleogenesis in the Pennington Formation, with the major controls being: 1) direct and diffuse recharge from the caprock, undersaturated with respect to calcite; 2) thin, horizontally bedded limestones sandwiched by shales and other insoluble rocks; and 3) networks of stress release fractures oriented parallel to major stream valleys. Our present understanding of the Cumberland Plateau could be advanced by further study of karst dynamics in the Pennington Formation.

Understanding how mountain landscapes respond to variations in tectonic forcing over a range of temporal scales in active mountain belts remains as a prominent challenge in tectonic and geomorphological studies. Although a number of empirical and numerical studies have examined this problem, many of them were complicated by issues of scale and climatic variability. More specifically, the relative efficiencies of fluvial and glacial erosion, which are presumably controlled by climate, are difficult to unravel. The Teton Range in Wyoming, which results from motion on the crustal-scale Teton fault, is an ideal natural laboratory for addressing this challenge as the tectonic uplift boundary condition and the variation of uplift along strike is well-documented by previous studies and due to its relatively small size, climate can be reasonably expected to vary consistently along strike. Here, we present the results from a study that examines how the Teton landscape responds across the longest (106-7 yrs) and shortest (102-4 yrs) temporal scales. Long-term canyon incision rates determined from apatite (U-Th)/He (AHe) analysis of major drainages are highest (0.24 mm yr-1) where measured uplift rates and duration are highest (near Mount Moran), leading us to propose that tectonic forcing operates as the first order control on long-term Teton erosion. Short-term denudation rates, which are derived by determining sediment volumes in Moran Bay that are deposited in catchments generated during the most recent glacial interval (Pinedale, ~15.5 ka), are 0.00303 – 0.4672 mm yr-1. We compare these rates to previous work, which found that high rock fall rates (1.13-1.14 mm yr-1) deposit large talus volumes in Avalanche and Moran Canyons. Despite their magnitude, such high rates of mass wasting are not sustained over long periods of time, as measured lake sediment volumes (0.007 km3) are. We conclude that the Tetons are transport limited during the interglacial and large volumes of canyon sediment generated during this time cannot be moved absent the advance of valley glaciers. That is, fluvial systems in small mountain systems are substantially less effective than glaciers in denuding mountain topography.

The Garlock Fault consists of three distinct segments, known as western, central, and eastern, together reaching approximately 260 km from the San Andreas Fault to the southern end of Death Valley. Although published slip rates are available along the western and central Garlock Fault segments, little is currently known of the Garlock Fault earthquake history or slip rate farther east. Using LiDAR and satellite imagery, the central and eastern Garlock Fault segments were analyzed for visibly offset, fault-adjacent, geomorphic surfaces that may potentially be used for estimating slip rate. Qualitative methods of assessing preserved alluvial surface maturity were adapted and used to establish unit age categories. Qualitative comparisons of late Pleistocene-Holocene surfaces reveal that the total offset at sites along the eastern Garlock Fault are less than half that of sites of comparable age along the central Garlock Fault, suggesting a significant reduction in slip rate across the intersection of the Brown Mountain, Owl Lake, and Garlock Faults. Digitally-measured offsets and their age groups were plotted in order to achieve preliminary slip-rate estimates. The resulting plot shows an eastward decrease in late Pleistocene-Holocene slip rate at sites along the central and eastern Garlock Fault segments. The central Garlock Fault slip-rate estimate taken from Slate Range West and Slate Range East sites in Pilot Knob Valley is approximately 4.2 mm/yr, within the error (but on the low side) of previously published rates. The slip-rate estimate from the Quail Mountains site, at the easternmost extent of the central Garlock Fault, is approximately 2.7 mm/yr. The slip-rate estimate from the Avawatz section of the eastern Garlock Fault is approximately 1.0 mm/yr.

The Haast Pass highway has had a long history of instability since it was constructed in 1960. Steep slopes and deeply incised river create an actively changing geomorphic environment making maintaining the highway corridor hazardous and difficult. This thesis study provides the first comprehensive investigation of the highway corridor between the Summit and Thunder Creek Falls using LiDAR and detailed air-photo analysis to provide the basis for geomorphic mapping. Management of slope hazards to date has been based on a reactive approach treating the immediate unstable areas around landslides after they occur. This study presents the first large-scale geomorphological assessment of the highway corridor identifying surface unit type, slope processes and slope hazards in order to facilitate the development of a long-term highway management strategy. Because dense vegetation covers nearly all the slopes above the highway in the study area as as such, it has not been possible to adequately investigate slope geomorphology until the availability of LiDAR. This study is the first to use Light direction and ranging[LiDAR] for corridor hazard mapping beneath dense vegetation in New Zealand. The LiDAR survey was flown by New Zealand Aerial Mapping in January 2014 for the New Zealand Transport Agency and was provided for use in this study. The LiDAR surface model created serves as the basis for mapping surface units and landslide features, enabling the identification of slope processes and landslide hazards. Aerial photos were also used to identify surface unit type and slope processes where vegetation was absent and enabled the activity of slopes to be evaluated. Interpretations made using LiDAR were validated using aerial photography and targeted ground truthing with all ground truthing sites confirming the interpretations made. Large scale geomorphology mapping was undertaken on slopes above the highway on the western side of the valley and showed that there were distinct differences between the southern and northern parts of the highway corridor. Between The Haast Pass Summit and Pipson Creek the slopes are dominated by schist bedrock with regolith confined to small deposits next to the highway and larger deposits in tributary valleys. The slope hazards affecting the highway in this zone are confined to debris sliding and rockfall from regolith deposits and bedrock cliffs next to the highway between Robinson and Pipson Creeks. The slopes between Pipson Creek and the Gates of Haast, in contrast, consist of deep regolith deposits and regolith veneered slopes. Evidence of active and recently active slope processes on the slopes facing the highway confirm the instability is associated with slope hazards including debris flows, debris slides, rock fall and highway collapse. Small-scale detailed evaluations were undertaken at Diana Falls, Ford Creek, The Hinge and the Gates of Haast with the sites selected based on their history of instability and/or their particu- larly hazardous appearance during the large-scale geomorphology and hazard identification. Using the LiDAR surface model surface units and landslide features were identified and mapped with small-scale engineering geomorphology maps. This information was then used to interpret the subsurface geometry and the failure mode/slope processes acting on the slope enabling an assessment of the current stability and future slope development to be made. Diana Falls was found to have scarps and tension cracks running across the regolith covered slope indicating that future landslides from this site will be an ongoing problem. At Ford Creek the landslide was identified as a rock compound slide, but assessments of its current stability and future development were unable to be made. Detailed investigations at The Hinge revealed evidence of a large creeping debris slide and the existence smaller debris slides below the highway through the entire investigation area; the debris slides identified show signs of activity and continued debris sliding will continue to affect the highway in the future. The investigation of the Gates of Haast revealed that the slope instability is not as extensive as it has been in the past, however, recent rock slides and debris flows have continued affect the highway and will continue to pose a hazard in the future. This thesis provides fundamental information required to develop a comprehensive management plan for the Haast Pass highway corridor between the Haast Pass summit and the Gates of Haast. A new landslide management plan has been developed outlining immediate, short-term and long- term options and programmes that should be implemented. Immediate options are steps that can be taken to quickly increase the safety of road users and include moving of highway closure gates and installation of warning signage. Short-term options aim to mitigate landslide hazards where feasible including the installation of rockfall barriers and debris flow attenuators, and lay the groundwork for future avoidance of hazards by undertaking investigations of highway realignment and developing highway closure rainfall thresholds. Long-term options are recommended where landslides will continue to impact the same section of the highway repeatedly and focus on hazard avoidance by building landslide shelters or major highway realignments. The adoption of a management plan ensures security of the highway, protects against loss of life and provides the most cost effective long-term solution to manage the landsliding hazards.