Academic literature on the topic 'Landforms'

O trabalho consiste na realização de um zoneamento geoambiental para a região de Piracicaba-SP, com base na análise de variáveis ambientais, principalmente de atributos do meio físico, tais como: geologia, solos, hidrologia, etc. A área estudada localiza-se na bacia hidrográfica do Rio Piracicaba, uma das mais importantes do estado de São Paulo e que vem apresentando intenso desenvolvimento econômico e consequentemente problemas de degradação ambiental. Este estudo foi realizado seguindo-se os pressupostos da cartografia geoambiental, mas utilizando-se também os procedimentos da cartografia geotécnica tradicional. Incorporou-se ainda ao estudo a utilização de um Sistema de Informações Geográficas (SIG) e do processamento digital de imagens de satélite, que permitiram maior agilidade e confiabilidade no levantamento, análise e tratamento das informações. Para a obtenção da carta de zoneamento geoambiental partiu-se da compartimentação do terreno em \"Landforms\", sendo que estas unidades homogêneas foram então caracterizadas e avaliadas quanto as suas principais aptidões e restrições. A carta obtida apresenta-se dividida em 16 unidades, descritas quanto a aptidões, restrições e conflitos de uso, principalmente em relação a aptidão agrícola, erosão, vulnerabilidade do aqüífero e disposição de rejeitos.<br>This work presents the geoenvironmental mapping of the Piracicaba (SP) region, based on the analysis of environmental attributes, such as: geology, soils and surface and ground waters. This region is located in the Piracicaba river basin, one of the more importance basins in the São Paulo state. It presents serious environmental degradation problems due to intense economic activities. This study has been based on the proposal of the geoenvironmental mapping, but using to the procedures of the traditional Engineering Geological Mapping. A Geographical Information System (IDRISI) and digital image processing were used to permit quickness and confidence on the collect, analysis and handling of the geological-geotechnical informations. The geoenvironmental zoning chart has been based on the terrain landforms division and the characterization of these homogeneous units that were evaluated with respect to the mainly aptitudes and constraints. The region was divided into 16 geoenvironmental units with their advantages and limitations analised in terms of agriculture aptitude, erosion susceptibility, aquifer vulnerability and waste disposal.

This thesis examines coastal form and sediments of the Marlborough Sounds, New Zealand. An important aspect of coastal behaviour in this landscape stems from linkages between catchment and coast. Focus is therefore placed on the manner in which sediment delivered from catchment sources is redistributed within the shore and offshore domains. Coastal response is shown to depend on two factors: the form of the receiving sites and the mobility of sediments within them. Investigation of coastal landforms at a range of scales identifies the framework within which sedimentation takes place. Consideration of landscape sediment redistribution at Quaternary, Holocene and human timescales establishes the locations in the coastal landscape in which change has taken place. A key factor in coastal response relates to the wide size range of sediments delivered. The fractionation of sediment within the coastal domains is used as an index by which to identify the controls on coastal sedimentation. A new conceptual model of coastal behaviour, the Ordered Response Model, is developed as a framework within which to investigate coastal response. The model is operationalised in three ways. This is done first with regard to coastal sediments and their grain-size interpretation, secondly in the context of shoreline form and sediment redistribution, and thirdly in relation to form and sediment trapping within coastal embayments. The patterns of sediment redistribution are seen to reflect trapping behaviour in the coastal landscape at a range of scales. Sediments are investigated from the viewpoint of the factors which determine their retention or accumulation in or rejection from a coastal site. Shore sites are distinguished on the basis of the extent to which they trap materials delivered to them from catchment sources. Governing factors are shoreline gradient and size grade of materials. A primary fractionation of sediments takes place at the shore and the finer fractions are by-passed to the nearshore. Sediment fractions that are relatively immobile under prevailing environmental conditions develop paved lag surfaces at a range of scales. Sediments that accumulate at the shore are distinctive in their mixed sand and xv gravel composition with a dominant mode in the granule and very coarse sand grades (-291 to 091). Sediment deposited on the intertidal surfaces is found to be redistributed by a distinctive mechanism. Migratory intertidal bedforms defined here as "clastic waves" are a means by which the low energy shores disperse sediment which is delivered to them. These waves are a distinctive form of the shoreline of the Marlborough Sounds, and have attributes different from other shoreline forms identified in the literature. Clastic waves are shore-parallel, crescentic or lunate forms with longshore crest dimensions of 0.5 to 30m, length dimension perpendicular to the crest of up to 20m, and crest heights of 0.05m to 0.5m. Rates of intermittent migration vary from 1m/day to 10m/year. Key factors in their development are identified as low wave energy, tidal range, intermediate to low intertidal gradients (<1:20) and a mixed sand and fine gravel grain-size. Bathymetric form is found to reflect the varying influence of sub-bottom morphology, sediment accumulation and hydraulic reworking. Analysis of sediment thickness identifies a mean thickness over sub-bottom of 7.33m in Pelorus Sound. Spatial variations in sediment thickness identifY marginal embayments as significant sediment traps. Mean sedimentation rates calculated over a 6,000 year timespan give Pelorus Sound a spatially averaged rate of 1.22mm/yr. Sub-bottom form is shown to have a stronger role in determining bathymetric form than previously reported. Due to the constraining effect of shallow sub-bottom form on sedimentary processes sediment thicknesses in the inner Pelorus Sound are not greater than those found in channels or embayments in the middle reaches of the Sound. A mean thickness of 5.75m from sub-bottom seismic profiles in the inner Pelorus equates to a sedimentation rate of 0.96mm/year over 6,000years, at about which time the river valleys of the Marlborough Sounds were drowned by postglacial rising sea-levels. Analysis of sub-bottom form reveals evidence of previously unreported drowned terrace remnants, which are correlated to subaerial terrace remnants. On the basis of both long profile patterns along these remnant surfaces and an analysis of bathymetric form of marginal bays and channels, an interpretation is developed of the origin of form in Pelorus Channel and Tory ChanneL Sediment trapping behaviour is identified as the most distinctive attribute of this coastal landscape, and shown to operate at a range of nested scales. As a XVI consequence of trapping behaviour, the operation of any part of this coastal landscape must be considered in relation to its operation as a whole.

This research is focused on mapping the geometries of surface and subsurface landforms and their relationship in the Niger Delta. Landforms on the surface are studied to improve our understanding of the spatial distribution of buried landforms. GIS techniques are applied to high resolution Landsat and SPOT imagery to map surface landforms, a necessary step in order to improve and better constraint subsurface modelling. Also, attributes from three dimensional seismic data are used to map buried landforms. Both techniques are focused on mapping the spatial distribution of landforms and analysis of their shape, size, orientation, connectivity and density. Results on the study of fluvial channels, point bars, braid bars, tidal channels, beach-barrier islands and spits are presented in this thesis. The updated map of the subarial Niger Delta covers an area of 70,000 km2. Tidal channel width increases exponentially toward the coast; in contrast the fluvial channel width decreases linearly downstream. Tidal channels are interconnected within a complex network. The tidal channels are wider in the East and West Flanks while in the centre they are narrower. Here, channel mouths are at a high angle with the coastline because of a combined effect of high sediment flux and longshore drift. Tidal channels are therefore grouped into four distinct zones; the West (Forcados River Zone), the Central (Nun River Zone), the East (Sombreiro River Zone) and the Far-East (Cross River Zone) based on their channel morphology and density. Each lobe is influenced differently by the interaction of fluvial, tidal and wave-related processes. This implies that it is appropriate to look at the Niger Delta as an amalgam of deltas geographically separated into four lobes. The morphology of the beaches also supports the considered reclassification, as they show distinct morphologies within each of the four lobes. Beaches are longer and wider on the eastern and western flanks and thin out towards the central lobe due to high sediment influx and wave reworking. Parallel channels form between scrolls and ridges and are prominent in areas where tidal influence does not extend far into the land. The correlation between the geometries of the surface and subsurface landforms is very strong and indicates that where subsurface details are missing, it is acceptable and reasonable to use surface information to make predictions about the subsurface. The result will help in constraining parameters used in modelling of geometric and dimensional properties of reservoirs and to better manage uncertainties, all elements relevant to the oil and gas industry.

The southern Chandeleur Islands are an ideal setting to study shoal evolution given their history of submergence and re-emergence. Here, numerical models shed light on the attendant processes contributing to shoal recovery/reemergence following a destructive storm event. Simulations of a synthetic winter storm along a cross-shore profile using Xbeach shows that convergence of wave-induced sediment transport associated with repeated passage of cold-fronts initiates aggradation, but does not lead to reemergence. A Delft3d model of the entire island chain shows that as these landforms aggrade alongshore processes driven by incident wave refraction on the shoal platform, backbarrier circulation and resulting transport become increasingly important for continued aggradation and eventual emergence. Aggradation magnitudes are a function of depth ranging from 2 – 10 mm per event (onset to recovery to near mean sea level). In the absence of big storms, this modest aggradation can be more than one meter in a few years.

<p>Kongsfjordhallet is situated at 79° N on the North coast of Kongsfjorden, Spitsbergen.The landscape shows a large diversity of landforms and sediments and the aim of thisstudy has been to investigate the spatial distribution and temporal differences betweenthese landforms.The most prominent landform is interpreted as a lateral moraine dividing the area fromsoutheast to northwest. This is probably a sign of a standstill during the deglaciation ofan ice-sheet glacier tongue filling the fjord. The valley-glaciers at Kongsfjordhallet haveadvanced after this event and left end moraines on top of the lateral moraine. Largeamounts of meltwater have eroded parts of the Kongsfjordhallet, creating several fossilmeltwater channels that dissect the landscape. Erratic boulders of mainly gneiss type arescattered all over the landscape, as high up as 500 m a.s.l. In addition to the erraticboulders, a lot of allochthonous material is found incorporated in local material,especially as a diamict interpreted as till that covers large parts of Kongsfjordhallet.The till can likely be correlated to one of the diamict units in the cliff sections at theKongsfjordhallet coast. At present, two large ravines drain the area, moving water fromthe glaciers to the ocean and a beach is developing in the Southeast part of the area dueto ocean transgression. Landforms from two glacial events are found, one regional andone local. An episode of high sea-level as well as fluvial and mass-wasting activity afterthe deglaciation is also recorded. The formation of the landforms in the area is believedto be after the Last Glacial Maximum and into the Holocene, but no absolute dates areavailable.</p><br>SciencePub

Current riparian zone assessments focus on the morphological features of the stream channel and ocular vegetation measurements. This procedure fails to address the hydraulic features responsible for the floristic structure and composition of the riparian zone. We looked at how the geology and landforms function as drivers of groundwater and surface-water exchange. These can mitigate watershed processes via groundwater availability to shape riparian processes; e.g. discharge, seasonality. We hypothesized that groundwater surface-water exchange is a first order process and that it dictates riparian water availability and that the underlying geology and landform can serve as a tool to gain greater understanding of a properly functioning riparian ecosystem. We tracked groundwater surface-water exchange using wells, piezometers, water temperature, conservative tracer injections and solute conductivity on an alluvial fan in the Gallatin valley. Southwestern Montana Conservative tracer injection indicated 3% tracer losses over the 1.5km reach. Through spring and summer 2011 groundwater wells and piezometers indicated flashy transient shallow groundwater. Significant late growing season stream discharge (~300 l/s) and standard riparian monitoring assessments would suggest a larger floristic community than what is present at the site. These metrics together suggest a disconnection between the surface-water and groundwater ultimately limiting the extent of the riparian vegetation community. We further determined that the surface water is disconnected from the local groundwater table. We conclude that the lack of surface water - groundwater connectivity drives the floristic structure and character of the riparian zone. Skewed or inaccurate views of riparian functionality may occur because; the current assessment fails to address surface water - groundwater connectivity.

Wollaston Peninsula and most of southern Victoria Island comprise Palaeozoic carbonate lowlands, scarps, and tableland situated between rises and arches of underlying Precambrian sedimentary and igneous rocks. Quaternary sediments are hummocky, thick and ice-cored near escarpments where ice flow resistance, thrusting and meltwater concentrated glacial debris; thinner, streamlined drift occurs in lowlands. Quaternary sediments are mainly Late Wisconsinan in age. Glacial sediments predominate but surficial raised marine and periglacial sediments are noted. Fluvial modification of the landscape is minor. Many of the spectacular glacial landforms on Wollaston Peninsula are streamlined and indicate formation under thick, warm-based (i.e. free subglacial water) glaciers. A set of distinctive landforms, including ground moraine (with small moraines and marginal channels), hummocky moraine, lateral moraines, and streamlined forms, relates to varying flow conditions within one major glacial advance. Stratified drift within moraines indicates the importance of glaciofluvial processes in addition to ice action. Collectively, these landforms record ice-marginal retreat, marginal stagnation following compressional flow, surging, flooding and regional stagnation during deglaciation. Freeze-on and ice stagnation trapped extensive bodies of drift-rich ice in zones of hummocky moraine. Arborescent networks of narrow eskers record subglacial meltwater drainage beneath major ice lobes and long broad eskers record subaerial deposition by meltwater of mainly supraglacial derivation. Late glacial events are dated relative to the incursion of the sea during deglaciation of northwest areas of Wollaston Peninsula by about 12 000 BP. Active ice-marginal conditions existed just before 10 000 BP, during formation of the large Colville moraines. Ice downwasted in the area causing glacier thinning. Prominent ground-ice features include pingos, thermokarst scars, and debris-flow lobes. Ground ice occurs as massive icy bodies, ice-wedge ice, and buried pingo ice. Based on its setting in hummocky moraine, its stratigraphy, debris content, and isotopic composition, the massive ice is likely buried glacial ice. Landscape modification by thermokarst erosion has produced ubiquitous diamictons similar to till, and landforms similar to glacial forms. Thick ground ice bodies exist only above marine limit and the limits of streamlined landforms because permafrost degradation occurred below these limits. Widespread thaw slumps and large-scale thermal contraction cracks also indicate ice-cored terrain.