<p> Mountaintop removal/valley fill (MTR/VF) coal mining in the Central Appalachian region has created the most extreme anthropogenic landscape on Earth by lowering ridges and infilling headwater stream valleys. No studies have attempted to detail erosional processes active on MTR/VR landforms. A combination of field work and LiDAR data observations documents erosional features on MTR/VF landscapes. Landscape evolution modeling explores future possibilities in valley-filled catchments. LiDAR data also allows for the quantification of valley-filled catchment alteration with statistically significant differences in both drainage density and depression storage capacity between &ldquo;less disturbed&rdquo; and valley-filled catchments. Field and LiDAR data observations show that the drainage systems associated with the periphery of the MTR/VF landscape are particularly vulnerable to gully erosion. This study also provides evidence of landslides occurring within fully reclaimed valley fills. Landscape evolution modeling reproduces gully erosion mechanisms documents in the field. Modeled erosion rates based solely on bedload averaged 10.9 mm/kyr^-1. Modeled erosion rates are higher on valley fills with constructed drains in the center of the valley fill relative to those with drains along the sides.</p><p>

<p> Few studies provide data that can document the long-term landscape evolution of the Piedmont of the southeastern United States. Here we present the results of field mapping and a soil chronosequence for fluvial terraces along a ~46 km reach of the Catawba River, NC and SC. Five terrace units (Qt1&ndash;5) have been mapped along the reach, and in certain regions a sixth surface (Qt0) was mapped. Observations of bedrock surfaces on Qt3&ndash;Qt0 confirmed that these units are strath terraces. Longitudinal profiles of terrace units constructed from mapping data revealed static channel convexities in Qt5&ndash;Qt1 in the lower reach of the study area at Landsford Canal State Park, and a lack of an obvious influence on terraces profiles within the Gold and Silver Hill shear zones in the middle reach. Age dating of terraces in this study included deriving ages based on surface height above the channel (Mills, 2000) and IRSL samples obtained from Qt3 exposures. Ages, reported in ka, are as follows: Qt0&mdash;4591 &plusmn; 404 ka, Qt1&mdash;1852 &plusmn; 365 ka, Qt2&mdash;1181 &plusmn; 194 ka, Qt3 (average of two IRSL ages)&mdash;142 &plusmn; 32 ka, Qt4&mdash;50 &plusmn; 8 ka, and Qt5&mdash;5 &plusmn; 2 ka. Up to 3 soil pits were dug on each terrace unit Qt5&mdash;Qt2, and soils described as per Birkeland (1999). Chronofunction trends of soil morphological properties include soil colors in the most developed B horizons reddening and clay films increasing in amount and prominence with surface age. Soil samples were analyzed for particle size, pedogenic iron (AAS), bulk density and major elements (XRF). Some of these analyses show expected trends with respect increasing surface age for terraces of the Catawba River, such as increases in clay content (%) and decreases in iron activity ratios in most weathered B horizons with increasing surface age. Overall the history Catawba River is one of five distinct periods of lateral planation of the valley, possibly driven by transitions to interglacial periods, punctuated by periods of incision, whose cause is currently unknown. The soil chronosequence, ages, and data derived from mapping, however, provide a strong foundation that can be used in further studies of the long-term landscape evolution of the SE Piedmont of the SE United States.</p><p>

Orientador: Mario Luis Assine / Banca: José Cândido Stevaux / Banca: Edvard Elias de Souza Filho / Banca: Archimedes Perez Filho / Banca: Cenira Maria Lupinacci da Cunha / Resumo: O megaleque fluvial do São Lourenço é um sistema deposicional que vem sendo construído pelo rio São Lourenço, desde o Pleistoceno, na porção nordeste da bacia sedimentar do Pantanal Mato-Grossense. Com base na interpretação de imagens orbitais e de dados de campo, foram reconhecidos três grandes compartimentos geomorfológicos no megaleque: a) uma extensa planície fluvial pleistocênica dissecada; b) um cinturão de meandros de idade holocênica, ainda ativo nas porções média/superior do megaleque, mas abandonado na sua porção distal; um lobo deposicional moderno composto por vários lóbulos deposicionais. Depósitos de diferentes compartimentos foram amostrados com vibrotestemunhador, sendo as facies sedimentares descritas e interpretadas em termos de processos e de ambientes deposicionais. As idades dos depósitos dos diferentes compartimentos foram obtidas por meio de datação pelo método de luminescência oticamente estimulada (LOE), o que permitiu a proposição de um modelo evolutivo para a área estudada. Na planície aluval dissecada foram reconhecidas paleorredes de canais distributários formados por lobos ativos durante o Pleniglacial médio, entre 64,8 e 28,5 ka AP. A planície aluvial dissecada foi submetida a processos erosivos, existindo na sua superfície uma rede de canais tributários, que drenam as águas das chuvas para as planícies fluviais periféricas dos rios Cuiabá e Piquiri. A maior evidência do evento de dissecação, que do final do Pleistoceno ao Holoceno superior, é a existência de um vale inciso na porção media/superior do megaleque, cortando os depósitos pleistocênicos dos lobos antigos. O vale tem direção N65E, condicionado pela falha de São Lourenço, e nele se encontra alojado o cinturão de meandros formado por agradação fluvial... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The São Lourenço fluvial megafan is a depositional system which has been built by the São Lourenço river since the Pleistocene in the northeastern region of the Pantanal sedimentary basin of Mato-Grosso State. Based on the interpretation of orbital images and collected data field, three major geomorphological compartments of the megafan were recognized: a) an extensive fluvial plain dissected in the Pleistocene; b) a meandering belt of Holocene age, still active in middle and upper parts of the megafan but abandoned in its most distal portion; and c) a modern depositional lobe consisting of several depositional lobes. Deposits of different compartments were sampled with vibrocorer and the recovered sedimentary facies have been described and interpreted in terms of processes and depositional environments. The ages of the deposits of the different compartments were obtained from dating by the optically stimulated luminescence method (OSL), which allowed the proposition of an evolutionary model for the study area. In the dissected alluvial plain, distributary paleochannels were recognized and formed lobes during the active Middle Pleniglacial, between 64,8 and 28,5 ka BP. The dissected alluvial plain was subjected to erosion, identified through the existence on its surface of a tributary drainage network which drains rain water to the peripheral alluvial plains of the Cuiabá and Piquiri rivers. The strongest evidence for dissection of the event, which starts from the late Pleistocene to the Holocene, is the existence of a valley in the middle/upper portion of the megafan, cutting through the Pleistocene deposits of ancient lobes. The valley has a N65E direction, conditioned by the São Lourenço fault, and it is housed in the fluvial meandering belt formed by aggradation of the valley during the Holocene. The heights of the... (Complete abstract click electronic access below) / Doutor

No description available.

Active layer detachments on the Fosheim Peninsula have been assumed to develop over periods of minutes to a few hours. This assumption played an integral role in the understanding of relationships between active layer detachment deposit morphology, morphometry and sedimentology and active layer detachment dynamics. Field observations of two failures at 'Big Slide Creek' on the Fosheim Peninsula in August 2005 showed that while one failure conformed to the pre-existing assumption of near-instantaneous formation, movement and cessation of movement, the other failure did not and exhibited progressive expansion over several days. Several active layer detachments known to have initiated in 2005 were visited in 2006 to assess whether active layer detachments known to have failed via a prolonged mode display surficial and internal morphological characteristics that are unique from active layer detachments known to have failed via a near-instantaneous mode and to evaluate the ability of the infinite slope model to adequately predict slope stability. Results have indicated that active layer detachments known to have failed via a prolonged mode display a number of surficial and internal morphological characteristics that differ from those at active layer detachments known to have failed via a near-instantaneous mode. Based on Factor of Safety calculations, peak effective stress stability analysis indicates that Fosheim Peninsula slopes should be stable if pore-water pressures are not artesian, whereas residual effective stress stability analysis indicates that slopes greater than 6&deg; on the Fosheim Peninsula are unstable even if pore water pressures are not artesian. Sensitivity analyses indicates that under peak conditions, Factors of Safety on Fosheim Peninsula slopes are most sensitive to changes in cohesion while under residual conditions, slope instability is related to increases in both slope angle and head of water above the slip plane.

This research statistically examined the topographic characteristics of rock glacier locations in the Yukon Territory and tested the suitability of the Canadian air photo collection for photogrammetrically measuring rock glacier velocities. A database of more than 1500 rock glacier locations in the Yukon was compiled. The topographic characteristics of rock glaciers in a 12% sample were compared by classifying the sample by morphology (lobate or tongue-shaped) and activity (active, inactive or relict) and testing the difference between the class properties of elevation, slope, aspect and area. Tongue-shaped rock glaciers occurred at significantly higher mean and minimum elevations than lobate forms. Active rock glaciers were significantly larger than inactive and relict forms, and active forms were significantly more north-facing than inactive forms. The photogrammetry study found that it is possible to measure rock glacier movement rates from multi-temporal air photos of the quality and frequency available for the Canadian North. It was also found that thermokarst development could be tracked on multi-temporal air photos, though its presence hinders the measurement of movement. With the continued acquisition of high quality photos, the technique should prove useful for monitoring both rock glacier movement and thermokarst development.

Buried esker systems are a major source of potable water in Eastern Ontario. Ever since the Clean Water Act was passed in 2006, efforts have been placed on understanding aquifers and characterizing watersheds in order to protect source water. This thesis focuses on one esker, extending from Vars to Winchester in the South Nation River watershed, which provides municipal water for seven villages -- an estimated population of 17,000. The esker complex is conceptualized as a 50-km long deposit of glaciofluvial outwash high-permeability material that is generally surrounded by fine, low permeability materials, except in a number of locations where the esker outcrops at ground surface. The complex recharges at its northern- and southern-most areas, which correspond to topographic highs; it discharges in a topographically low area at its center near the village of Embrun. Regional stratigraphy was simplified for modeling purposes and brought down to six hydrostratigraphic units, two of which represent the esker: a coarser core, composed of a mixture of coarse sand and gravel, and sandy fan deposits. A three-dimensional hydrogeological model was developed using a finite element groundwater flow system, FEFLOW. Recharge and hydraulic conductivities were adjusted during calibration. Calibration was assessed using the mean error of residuals, standard deviation of residuals and normalized Root Mean Square calculations; correlation was estimated using the determination coefficient and Pearson's coefficient. Results favour the conceptualization of the esker as a continuous, heterogeneous deposit comprising a gravelly core and sandy fans (ME=-4.33m, RMS=5.67m, n=18 wells in close proximity of esker); however, mean residuals are not significantly different when testing the discontinuous and homogeneous esker hypotheses. Sensitivity analyses testing the model's response to recharge and pumping showed that the system is relatively resilient; however, our better judgement tells us that this is an artefact due to boundary conditions and not an adequate prediction of what may happen. Nevertheless, we hope this model will be a facilitating tool for understanding, managing and protecting the aquifer's resource.

In May 2008, high frequency ground penetrating radar (GPR) surveys were conducted on the Belcher Glacier Basin, Devon Ice Cap, and validated with avalanche probe measurements to map the thickness and spatial variability of winter (2007-8) snow. The GPR record was combined with field measurements using a neutron density probe and correlated with NCEP-NCAR climate reanalysis, QSCAT satellite records, and airborne ASIRAS data to derive multi-year snow accumulation patterns across the basin from 2005-7. The distinct characteristics of the GPR record from the surface to 3 m depth were related to the 2007 and 2005 summer surfaces. GPR derived depths to these surfaces and the assessment of the average annual accumulation rate across this basin correlate very well with previous snow accumulation assessments in other parts of Devon Ice Cap (Mair et al. 2005, Colgan et al. 2008 and Koerner 1977). The complex radar returns in the LSS-05 depth range appear to be related to extensive melt processes during summer 2005, together with a large rain event in summer 2006, which produced large quantities of meltwater at all elevations of Devon Ice Cap. The major broad-scale control factor in determining annual and multiyear snow depth patterns for the basin is elevation, with surface topography and distance from the moisture source being locally important. GPR enabled the position of the basin-wide snow line to be determined by observing internal layers emerging at the surface, with the superimposed ice facies and equilibrium line altitude inferred below this altitude.

<p> Thermokarst lakes are a dominant factor of landscape scale processes and permafrost dynamics in the otherwise continuous permafrost region of the Arctic Coastal Plain (ACP) of northern Alaska. Lakes cover greater than 20% of the landscape on the ACP and drained lake basins cover an additional 50 to 60% of the landscape. The formation, expansion, drainage, and reformation of thermokarst lakes has been described by some researchers as part of a natural cycle, the thaw lake cycle, that has reworked the ACP landscape during the course of the Holocene. Yet the factors and processes controlling contemporary thermokarst lake expansion remain poorly described. This thesis focuses on the factors controlling variation in extant thermokarst lake expansion rates in three ACP regions that vary with respect to landscape history, ground-ice content, and lake characteristics (i.e. size and depth). Through the use of historical aerial imagery, satellite imagery, and field-based data collection, this study identifies the controlling factors at multiple spatial and temporal scales to better understand the processes relating to thermokarst lake expansion. Comparison of 35 lakes across the ACP shows regional differences in expansion rate related to permafrost ice content ranging from an average expansion rate of 0.62 m/yr on the Younger Outer Coastal Plain where ice content is highest to 0.16 m/yr on the Inner Coastal Plain where ice content is lowest. Within each region, lakes vary in their expansion rates due to factors such as lake size, lake depth, and winter ice regime. On an individual level, lakes vary due to shoreline characteristics such as local bathymetry and bluff height. Predicting how thermokarst lakes will behave locally and on a landscape scale is increasingly important for managing habitat and water resources and informing models of land-climate interactions in the Arctic.</p><p>

No description available.