Dissertations / Theses on the topic 'Slope (Physical geography)'

The study evaluates widely used slope estimation algorithms with the aim of determining similarities or differences between results obtained by each, the accuracy of methods in modelling actual slope, and the suitability of these methods for site-specific and non-site specific applications. The data used in the study comprise of 24 artificial surfaces generated from mathematical equations and a natural surface represented by a USGS Digital Elevation Model of the Salem Quadrangle, Virginia. The concept of using artificial surfaces was to enable determination of accuracy without the requirement for field observations. The gradient calculated from partial derivatives of the equations was used to compare results from different methods. The natural surface was used to validate the findings of the study on artificial surfaces. The results were then statistically evaluated using ANOVA and regression analysis. It was found that the methods could be used interchangeably for non-site-specific applications while for site-specific applications the differences could be very significant.
Master of Science

This study of slope instability in the Matlock region of Derbyshire uses, and tests the applicability of, a variety of techniques from reconnaissance through to site investigation. The aims have been to (i) provide a greater understanding of landsliding in this area and (ii) produce a critical assessment of the techniques employed. A procedure was developed for the application of Landsat-5 TM imagery to slope stability studies, however, such imagery was found to be of very limited use in the study area. Morphological and geomorphological mapping from aerial photographs and in the field proved to be of greatest use for supplying information on landslide location, morphology, type and recent activity, and also in identifying surface water conditions. These techniques are relatively rapid, require the minimum of equipment, and provide a large amount of relevant data in a short time. They are also applicable to both reconnaissance surveys and site investigations. The geomorphological survey of Oker Hill near Matlock revealed a large multiple rotational landslide. An ochre-precipitating spring is situated within this landslide. A similar spring occurs on Mam Tor landslide in north Derbyshire, and Vear (1981) has shown this to be evidence of pyrite oxidation of the shale, a process which is believed to lead to periodic slope failure. Analysis of core material from two boreholes through the Oker Hill landslide confirmed that pyrite has been lost from the failed material and that the present base of the weathered zone is in the pyritic shale. Pyrite oxidation is resulting in iron oxide staining, the loss of sulphur (presumably as sulphuric acid which will participate in further reactions) and in an overall deterioration of the rock quality of the shale.

The Arctic contains a wealth of landforms that are governed by the diurnal and seasonal response of permafrost to climatic and topographic forcings. Of key importance to the process rates of many periglacial landforms is the dynamic behaviour of the active layer, which regulates the transfer of heat and moisture between the atmosphere and permafrost. The strong dependence of periglacial process rates on active layer dynamics makes this geomorphic system particularly sensitive to future increases in Arctic temperatures and precipitation. These increases will continue to degrade permafrost, affecting the distribution and rates of periglacial processes. I develop a landform classification model on Svalbard that reveals solifluction and scree to be the most dominant hillslope processes acting on this landscape, with sediment fluxes greatest in solifluction. A combination of landslide mapping, solifluction modelling and slope stability analysis in Alaska reveals that landslides are coincident with convergent topography on soliflucting hillslopes that have concentrated ground ice at depth. Convergent topography allows for higher moisture availability that feeds the growth, concentration, and development of a large network of ice lenses at the permafrost/active layer boundary. The excess pore pressures generated upon thaw reduces the shear strength of soil at the base of the active layer, causing it to slide downslope along a planar slip surface on top of the unthawed permafrost. Due to a warming Arctic, permafrost is expected to continue thawing, creating an ever more dynamic and deeper active layer. Consequently, the relative regional extent of periglacial landforms in mountainous Arctic environments is expected to change, with Arctic hillslopes becoming more unstable during extreme summer thawing. This will pose a greater hazard to Arctic infrastructure and act as a major force for environmental and geomorphological change.

Rainier, Oregon, has experienced problems in the development of residential and commercial sites, utilities, and transportation facilities as a result of slope instability. This study of slope stability at Rainier was conducted at the request of city officials.

Research on hillslope surface processes and hillslope stratigraphy has been neglected in southern Africa. The amount of published literature on hillslope stratigraphy in southern Africa is very limited. Hillslope sediments provide a record of past environmental conditions and may be especially useful in calculating the recurrence interval of extreme environmental conditions such as earthquakes and intense rainfall events. The characteristics of hillslope sediments provide information as to their origin, transport and mechanisms of deposition. No published work could be found that had been undertaken on hillslope surface processes or stratigraphy in the eastern Cape coastal region. This study attempted to fill this gap in the geomorphic literature for southern Africa. The surface processes acting on hillslopes at Burchleigh and Spring Grove in the Alexandria district of the eastern Cape were examined in terms of slope morphology, surface sediment characteristics and the internal geometry of the hillslope sedimentary deposits. The late Quaternary hillslope sedimentary deposits at the two study sites are composed of fine grained colluvial sediments intercalated with highly lenticular diamicts. The fine grained colluvial sediments were emplaced by overland flow processes while the diamicts were deposited by debris flows. The sedimentary sequences at both study sites have a basal conglomerate interpreted as a channel lag deposit. Most slope failures preceding debris flow events were probably triggered by intense or extended periods of rainfall associated with cold fronts or cut-of flows. Seismic events may also have triggered slope failure, with or without the hillslope sediments being saturated. The results of this study indicate that a continuum exists between the slopewash dominated processes of the presently summer rainfall regions of Natal to the present winter rainfall regions of the western Cape where mass movement processes are significant. Hillslope deposits, therefore, provide a record of environmental conditions which may greatly facilitate proper management of the landscape.

Pore water pressure in a silt slope in Sollefteå, Sweden, was measured from 2009-2016. The results from2009-2012 were presented and evaluated in a publication by Westerberg et al. (2014) and this report is an extension of that project.In a silt slope the pore water pressures are generally negative, contributing to the stability of theslope. In this report the pore water pressure variations are analyzed using basic statistics and a connection between the pore water pressure variations, the geology and parameters such as temperature, precipitation and soil moisture are discussed.The soils in the slope at Nipuddsvägen consists of sandy silt, silt, clayey silt and silty clay. The main findings were that at 2, 4 and 6 m depth there are significant increases and decreases in the pore water pressure that can be linked with the changing of the seasons, for example there is a significant increase in the spring when the ground frost melts. As the seasons change, so do the temperature and amount and type of precipitation. Other factors that vary with the season are the amount of net radiation, wind speed and relative humidity, all of which affect the amount of evapotranspiration. At greater depths the pore water pressue is most likely affected by a factor/factors that varies from year to year, possibly the total amount of rainfall. Therefore, the anticipated increase in precipitation in Scandinavia due to climate change could be an important factor influencing slope stability.What precipitation, temperature and evapotranspiration have in common is that they affect the amount of water infiltrating the soil, and thereby the soil moisture content. How the soil moisture is distributed and flows through the soil (sub-surface flow) is governed by the different soil types and their mutual order in the slope, as well as by factors affecting the structure of the soil, e.g. animal burrows and aggregation. The formation of ground frost also affects the way in which the water present in the soil is redistributed.At c. 14 m depth in the slope, there is a saturated layer with positive pore water pressures, which could be one of several such layers. The overall groundwater situation in a silt slope is complex; several different bodies of water can develop, and to get a complete picture of the ground water situation (andthereby also the pore water pressure variations) thorough hydrological surveys are needed.
Under  2009-2016  mättes  porvattentrycket  i  en  siltslänt  i  Sollefteå.  Resultaten  från  2009-2012presenterades och utvärderades i en publikation av Westerberg et al. (2014) och detta examensarbete är en förlängning av det projektet.I en siltslänt är porvattentrycket vanligtvis negativt vilket bidrar till stabiliteten i slänten. I den härrapporten är variationerna av porvattentrycket analyserade med hjälp av enkel statistik och en koppling mellan variationerna och geologin samt parametrar så som temperatur, nederbörd och fukthalt i marken diskuteras.Jordarterna i slänten vid Nipuddsvägen består av sandig silt, silt, lerig silt och siltig lera. Slutsatsen var att på 2, 4 och 6 m djup ökade och minskade porvattentrycket med årstiderna, till exempel ökade porvattentrycket signifikant vid tjällossningen. När årstiderna skiftar ändras även temperaturen och mängden, och typen, av nederbörd. Andra faktorer som varierar över året är netto-instrålningen, vindhastigheten och den relativa fuktigheten och dessa faktorer påverkar i sin tur evapotranspirationen. På större djup beror antagligen portrycksvariationerna på någon eller några faktorer som skiljer sig åt från år till år, möjligtvis den totala mängden nederbörd. Därmed skulle den ökade nederbörd som förväntas i Skandinavien på grund av klimatförändringarna kunna påverka släntstabiliteten.Vad nederbörd, temeperatur och evapotranspiration har gemensamt är att de påverkar mängden vatten som infiltrerar marken, det vill säga de påverkar markens fukthalt. Hur vattnet är födelat i marken beror på de olika jordarterna och deras inbördes ordning i slänten, men också av faktorer som påverkar markens struktur så som aggregation och uppluckring av jorden på grund av marklevande djurs aktivitet. Även formationen av tjäle på vintern har troligtvis en viss inverkan på hur vattnet i marken omfördelas.På 14 m djup finns ett vattenmättat lager med positiva porvattentryck vilket skulle kunna vara ett av flera sådana lager. I en siltslänt är grundvattensituationen mycket komplex, flera magasin av vatten kan bildas. För att få en bra bild av grundvattensituationen (och där med också porvattentrycksvariationerna)behöver noggranna hydrologiska undersökningar genomföras.

Slope processes are important to understand if we are to protect fragile environments. Every year slope development in weak soils put nearby infrastructure in risk zones of sliding and ravine erosion takes away field areal from farmers as they grow even larger. Many methods for doing a risk analysis of a slope and its soil are complicated and require a lot of equipment. A simple way to do a slope investigation is explained in this report, along with its advantages and disadvantages. The authors construct a shear ring, an apparatus to measure peak shear stress of soils before fracturing. LIDAR scanning of two small ravines are also made to illustrate how laser scanning can be used to accurately measure denudation in slopes. The results vary, the shear ring is mostly a success aside from errors caused by difficulty in taking representative samples and disturbance. Some of the laboratory work made to determine material properties fail at giving good results, often a result of bad samples or disturbance in the tests. The LIDAR is determined to be a good instrument when working with slope development.
Sluttningsprocesser är viktiga att förstå och studera om vi ska kunna skydda känsliga områden. Varje år så sätter svaga jordar i sluttningar närliggande infrastruktur i riskzonen för att ligga på ett glidplan som snabbt kan släppa om jorden blir för blöt eller om för mycket tyngd läggs ovanpå. Samtidigt så tar ravinerosion bort åkerareal från bönder varje år medan ravinerna blir större och större. Många metoder för att göra riskanalyser av sluttningar är komplicerade och kräver mycket utrustning. I denna rapport så testas ett enkelt sätt att göra en sluttningsanalys med tillhörande diskussion kring dess fördelar och nackdelar. Författarna konstruerar en shear ring, en apparat som används för att testa jordens möjlighet att motstå en applicerad kraft. Två sidoraviner scannas även med LIDAR som en bas för att studera denudation i sluttningar. Resultaten varierar, shear ring-apparaturen bestäms som väl fungerande med undantag från vissa utförda tester, där svårigheter uppstod då jordproverna var störda eller mindre representativa. Vissa av laborationerna på jorden misslyckas med att ge bra värden, vilket ofta är ett resultat av dåliga eller störda prover. Laserscanningar av raviner med LIDAR bestäms som ett bra sätt att studera utvecklingen i sluttningar samt att mäta erosion.

Antiscarps are defined here as any uphill facing scarp that may be observed on slopes, regardless of size or scale. They are not present on all slopes, but where they have been observed, they typically occur sub-parallel to the valley axis near the ridge crests in mountainous regions. Antiscarps are generally, but not exclusively, found in glaciated regions, where loading and unloading of the rock mass has effected changes to the in situ stress fields through cycles of compression and elastoplastic rebound and has also removed large volumes of material by the formation of cirques. Non-glacial antiscarps are commonly associated with tectonic activity. An extensive review of current literature has been used to assist in the identification of key parameters associated with antiscarps and to provide a basis for clearly defining the terminology used to address antiscarp related processes and features. All of the reviewed material has been collated into a chart where the factors that have been extracted from the articles are grouped and compared. The chart has been instrumental in selecting the nomenclature to be used when addressing different types of antiscarp and also in constraining the extent to which the term can be reasonably used. A flowchart has been developed to assist in the identification of the primary antiscarp forming process. The flowchart was successfully used to identify the primary processes associated with antiscarps observed in field studies in both the South Island of New Zealand and in the Scottish Highlands. Physical base friction models and numerical finite element modelling, using Plaxis v6.1 and FLAC 2D v3.40, both indicate that antiscarps can form solely under a gravitational load. Base friction models used individual elements of various geometries. Antiscarps formed in most of the models and were best identified in models that had a clearly defined discontinuity surface. The numerical models also indicate that shear along existing discontinuities is the dominant mode for the formation of antiscarps under a gravitational load in homogeneous massifs.

Numerous forest fires occurred during the summer of 2004 in the Klondike Goldfields region of the Yukon Territory, an area of extensive discontinuous permafrost. More than 35 shallow detachment failure landslides developed in subsequent weeks in Steele Creek, a small drainage basin located about 60 km south of Dawson City. Preliminary observations of the failures and near-surface thermal regime were made through freeze-up of 2004 and continued in the summers of 2005 and 2006. Detachment failures were mapped and individual sites were surveyed. Air and ground temperatures were measured in burned and unburned areas. In addition, two-dimensional DC resistivity transects were used to examine subsurface conditions in the area. Forest fire contributed to detachment failure activity on permafrost slopes by destroying the surface organic mat, causing burned surface temperatures to rise, thawing active layers by up to 20 cm (+31%) deeper than unburned slopes and weakening the surface root structures. Deeper thaw melted transient layer ground ice, raising soil porewater pressures. The thermal differences between burned and unburned sites were greater at the north-facing than south-facing sites, and active layer freezing and thawing processes varied according to both aspect and burned status. More southerly-facing and/or burned sites generally thawed earlier, refroze later and had warmer temperatures than more northerly and/or unburned sites. Thaw of burned areas with high ground surface temperatures can be expected to continue, depending on climatic conditions, until sufficient revegetation occurs to shade the surface and rebuild the insulating organic mat. The detachment failures occurred from a few weeks to two years after forest fire, and only on slopes where permafrost was extensive. They were not similar to others in the literature in that almost all occurred in coarse-gained soils and had failure planes elevated above the permafrost table. These landslides were flow-type failures that rafted portions of the organic mat on top of deforming, non-cohesive sediment. They occurred in areas of deeper thaw but their distribution and the resistivity data suggest that they were associated with supra-permafrost taliks which concentrated groundwater flow. In an unglaciated area like the Klondike region this landsliding process has likely occurred thousands of times during the Pleistocene and may be responsible for elements of the form of the region's slopes. Predicted increases in the frequency and magnitude of forest fire in the boreal forest due to warming climates may increase incidence of these types of failures.

Orientador: Regina Célia de Oliveira
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências
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Resumo: O estudo ambiental tem revelado sobretudo nas últimas décadas, um caráter interdisciplinar nas pesquisas pautadas sobre a dinâmica dos agentes naturais, frente à crescente pressão de uso do espaço, materializada por conflitos de diversas ordens, sejam esses, históricos, políticos, culturais, religiosos, enfim, relações humanas que se estruturam sobre o território e impõem a esse espaço níveis diversos de interferência no mecanismo natural preexistente. Nesse contexto, entender as relações das sociedades humanas com a natureza, dentro de uma perspectiva absolutamente dinâmica, que envolve os aspectos culturais, sociais, econômicos e naturais, exige adotar um procedimento analítico que leve em consideração a sociedade nos seus diversos estágios de desenvolvimento, e remeta a uma visão holística da organização do espaço. Sendo assim, a ciência geográfica, tendo como objeto de análise o espaço geográfico, possibilita, sob um olhar crítico, a realização de estudos ambientais integrados, de maneira a dar suporte técnico científico para a elaboração de estudos como aqueles relacionados ao zoneamento ambiental, que podem estar inseridos nas políticas públicas, contribuindo no planejamento e tomada de decisão. Considerando o exposto, esta tese se propõe à elaboração de um Zoneamento Ambiental, como subsidio ao planejamento do uso e ocupação das terras da zona costeira da região Costa do Descobrimento, situada na região Extremo Sul do Estado da Bahia. Tal proposta de estudo justifica-se por três fatores: (a) essa região é uma das áreas de povoamento pioneiro do território nacional, área em que o agente antrópico atua como ator na configuração da paisagem há mais de cinco séculos; (b) a área tem sofrido transformações no uso e ocupação das terras, não considerando os níveis de fragilidade ambiental da área em estudo, o que acentua os problemas ambientais; e (c) a inexistência de estudos que integrem os sistemas naturais aos sistemas antrópicos no planejamento no uso e ocupação da zona costeira da região Costa do Descobrimento. Nos últimos quarenta anos, ela se tornou uma das regiões mais dinâmicas economicamente do Estado da Bahia, e também é um dos principais destinos turísticos do Brasil. Para atingir tal meta, adotou-se a metodologia proposta por Rodriguez, Silva e Cavalcanti (2004), enfatizando a análise funcional da paisagem. As diferentes atividades econômicas implantadas na Região Costa do Descobrimento, nos últimos 40 anos possibilitaram a formação de diversos sistemas ambientais com fragilidades complexas e que sofrem há séculos pressões de uso, resultando em problemas ambientais que alteram a dinâmica dos sistemas naturais e também o modo de viver da população local
Abstract: The environmental study has revealed especially in recent decades in an interdisciplinary research guided on the dynamics of natural agents face the growing pressure of space usage, embodied by conflicts of various orders, are those, historical, political, cultural, religious, in order, human relations that are structured on the territory and impose on this space several levels of interference in the natural pre-existing mechanism. In this context, understanding the relationship of human societies and nature, within an absolutely dynamic perspective that involves cultural, social, economic and natural, requires adopting an analytical procedure that takes into account the society in their various stages of development, which refers to a holistic view of space organization. Thus, the geographical science as the object of the geographic analysis, allows a critical eye on the implementation of integrated environmental studies in order to provide technical support for the development of scientific studies such as those related to environmental zoning that can be inserted on policy contributing public in planning and decision taken. Considering the above, this thesis proposes the development of an environmental zoning as support for planning the use and occupation of the coastal region of the Discovery Coast, located in the extreme south of Bahia. This proposed study is justified by three factors: (a) this region is a pioneer of the populated areas of the country, an area in which the agent acts as man-made actor in shaping the landscape for more than five centuries, (b) area has undergone significant changes in the use and occupation of land, not considering the levels of environmental fragility of the study area, which emphasizes environmental issues, and (c) the lack of studies integrating natural systems to anthropogenic systems in use in planning and occupation of the coastal region of the Discovery Coast, that the last forty years has become one of the economically most dynamic regions of the state of Bahia, and is also one of the major tourist destinations in Brazil. To achieve this goal, we adopted the methodology proposed by Rodriguez, Cavalcanti, Silva and Cavalcanti (2004), emphasizing the functional analysis of the landscape. The different economic activities implemented in the Discovery Coast Region in the last 40 years has enabled the formation of different complex environmental systems with frailties and suffering centuries of use pressures resulting in environmental problems that affect the dynamics of natural systems and also the way of life of local population
Doutorado
Análise Ambiental e Dinâmica Territorial
Doutor em Ciências

Orientador: Francisco Sérgio Bernardes Ladeira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências
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Resumo: Os movimentos de massa são fenômenos naturais de evolução das vertentes, mas eles causam grandes estragos sendo considerados como risco quando em uma área se têm a vulnerabilidade na escarpa associada a ocupação humana ou industrial que traga risco a população. A área de estudo fica localizada no litoral norte do Estado de São Paulo, Brasil. Na região da Serra do Mar, uma escarpa que chega aos 1.000m de altitude, funciona como uma barreira orográfica fazendo com que a área seja intensamente atingida por precipitações, sendo que o município atinge médias anuais muito altas. Para o estudo completo desses fenômenos é importante conhecer melhor a estrutura dos solos e seu comportamento em relação a dinâmica da água, por isso o objetivo deste trabalho foi de realizar esta caracterização e verificar o possível local de ruptura entre horizontes do solo. A área escolhida para o desenvolvimento do estudo têm altos índices pluviométricos e histórico desses tipos de movimentos de massa gravitacionais. Para a realização deste trabalho foram realizadas análises macromorfológicas de campo com descrição dos perfis levantados (três), de mineralogia, índices de Atterberg (limite de plasticidade e de liquidez), curva de retenção da água nos horizontes do solo e resistência ao cisalhamento. A granulometria analisada foi diversificada, encontrando solos argilosos e areno-argilosos, tendo predominância o Argissolo Vermelho Amarelo Álico. A maior profundidade encontrada foi de 227cm e a menor de 175cm; as curvas mostraram resultados de retenção diferentes para cada horizonte, mostrando os diferentes comportamentos em relação a retenção da água; os limites acompanharam a granulometria, tendo atingido valores maiores para solos mais argilosos, como os encontrados na trincheira 02; e a resistência ao cisalhamento também mostrou diferença nos valores dos parâmetros (coesão e ângulo de atrito interno) entre os horizontes, neste ensaio os solos da trincheira 03 não foram utilizados, pois ela estava localizada próxima a base da encosta. Os resultados nos levam a entender que o contato entre esses horizontes (B e C) é um ponto susceptível a ruptura
Abstract: The mass movements are natural phenomena of evolution of the slopes, but they cause great damage when being considered as a risk in one area if they have a vulnerability in the slope associated with human occupation or industry that brings risk population. The study area is located on the northern coast of São Paulo, Brazil. In the region of Serra do Mar, an escarpment that reaches 1,000 m above sea level, acts as an orographic barrier causing the area is heavily affected by rainfall, and the average annual county reaches very high. For the complete study of these phenomena is important to better understand the structure of soils and their behavior in relation to water dynamics, so the aim was to achieve this characterization and to determine the possible site of rupture between soil horizons. The area chosen for the development of study have high rainfall and history of these types of gravitational mass movements. For this work were analyzed macromorphological field describing the profiles surveyed (three), mineralogical, Atterberg limits (plastic limit and liquid), water retention curve in soil horizons and shear strength. The particle size analysis was diversified, finding clay soils and sandy-clay, with the predominance Alfissol Álico. The greatest depth found was less than 227cm and 175cm, the retention curves showed different results for each horizon, showing the different behaviors in relation to water retention; followed the grain boundaries, reaching higher values for more clayey soils, as those found in the trench 02, and shear strength also showed differences in the values of the parameters (cohesion and internal friction angle) between the horizons, to test the soil of the trench 03 were not used because it was located near the base of the slope. The results lead us to believe that contact between these horizons (B and C) is a point likely to break
Mestrado
Análise Ambiental e Dinâmica Territorial
Mestre em Geografia

Limestone and dolomite quarries were mapped to determine specific slope failure mechanisms for the various geological and structural conditions. Wedge failure and plane failure were determined to be the most influential mechanisms. Algorithms for analyzing these mechanisms were incorporated into the software package PSLOPE. The program is designed to facilitate progressive stability evaluation of quarry high walls as mining continues and permits calculation of safety factors and probabilistic reliability. Safety factor evaluations with the potential for back-analysis and sensitivity studies are included to investigate alternative high wall designs. Reliability analysis using Monte Carlo sampling minimizes uncertainty and allows the use of all available data in a stability evaluation. E~tensive "help" menus are incorporated into the program. The "help" menus include ranges of physical properties such as cohesion and friction angle for specific lithologic units determined from published research. This package includes an optimum design protocol that can be followed to avoid massive failure. The program was developed in conjunction with the quarry industry and is demonstrated through technical problem solving and a detailed case study. A large carbonate quarry in the eastern U.S. was studied in detail to demonstrate the utility of PSLOPE.
Master of Science

Orientador: Ricardo Ribeiro Rodrigues
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A partir dos anos 90, a conscientização da sociedade e o aumento do atendimento à legislação ambiental fizeram proliferar muitas iniciativas de recuperação de áreas degradadas. A transposição do topsoil, rica fonte de sementes nativas e de matéria orgânica, deve ser uma técnica alternativa promissora. O topsoil já vem sendo utilizado com sucesso, mas sua aplicação ainda está restrita a áreas planas. A disponibilidade de topsoil associada à necessidade de recuperação de taludes com espécies nativas, inspirou a presente pesquisa. O objetivo foi avaliar a possibilidade de uso da técnica de transposição de topsoil para a recuperação de taludes de corte e aterro, identificando os fatores atuantes na sucessão secundária inicial da comunidade de plantas e suas implicações para a recuperação. Em um talude com inclinação de 30º foi depositada a camada de topsoil proveniente de uma área de floresta recém desmatada. Foram utilizadas quatro técnicas de contenção do topsoil depositado: madeiramento formando terraços (M), sulcos horizontais (S) e cada uma, M e S, associadas a linhas de adubação verde semeada (MAV e SAV). O delineamento experimental foi o de blocos ao acaso, em que cada tratamento possui três réplicas de 12x15 m2, distribuídas em três blocos. A densidade de indivíduos regenerantes e a riqueza de formas de vida foram monitoradas por 14 meses, e a porcentagem de solo exposto foi avaliada no último mês. Após os 14 meses foram registradas 150 espécies de todas as formas de vida. Os tratamentos apresentaram densidades cinco vezes maiores que o testemunho, variando de 5,2 a 22,6 indiv/m2, mas não foram diferentes entre si. O tratamento de sulcos (S) apresentou a maior porcentagem de solo exposto (Capítulo 1). Mais do que os tratamentos as características do topsoil e a densidade do banco de sementes do topsoil, diferentes entre os blocos experimentais, determinaram padrões distintos de colonização, de estrutura e de velocidade de recuperação das comunidades (Capítulo 2). Se observada a área experimental como um todo, formou-se uma comunidade heterogênea florística e estruturalmente, o que deve ser interessante para áreas em regeneração. Os resultados indicaram que a recuperação de taludes pode ser eficiente utilizando a técnica de transposição de topsoil desde que sejam utilizadas técnicas de contenção conjuntamente. Com a metodologia proposta, ampliam-se as possibilidades de uso do topsoil e possibilita-se a recuperação de taludes de corte e aterro com espécies nativas
Abstract: After the nineties, the awareness of the society and enhancement of legal environmental requirements resulted in a greater number of initiatives on degraded lands rehabilitation. The use of topsoil, which contains the forest seed bank and high concentrations of organic matter, has been successfully used, but its application still restrict to flat or low-declivity areas. The local availability of topsoil together with the necessity to rehabilitate slopes with native species community inspired this experimental research. The purpose of this study was to evaluate the topsoil transposition technique to rehabilitate slopes, aiming to identify the main factors acting over the initial succession of these communities and its implications for the rehabilitation process. At an embankment slope with 30° declivity we spread the topsoil collected in a surrounding area just after forest clear cut. Four contention techniques were tested: wood fences forming terraces, horizontal rips, wood fences with green manure and horizontal rips with green manure. The experiment was designed in casualized blocks were each treatment has three 12 x 15m2 replicas, distributed in three blocks. We monitored the regenerating community for 14 months, measuring the individual¿s density and the life forms richness. The percentage of exposed soil was measured on the last sampling. Afther 14 months, we registered 150 species including all life forms. In all treatments, the density of individuals was at least five times higher than in the control, ranging from 5,2 to 22,6 ind/m2. The density of individuals was not different among the four treatments, but the rips treatment showed the highest percentage of exposed soil (Chapter 1). The allochtonous soil characteristics, diferent among the experimental blocks, were the main determinants of the structure and floristic composition of regenerating communities. Differences of topsoil soil fertility and seed bank density determined different initial colonization patterns, as well as the community final structure and recovery speed (Chapter 2). Analyzing the whole experimental area, the growth of distinct communities at the same rehabilitated area resulted in a community with heterogeneous structure and floristic composition, which may be interesting for regenerating areas. The results showed that, together with contention techniques, the topsoil use as a source of propagules and organic matter can be efficient on slopes¿ rehabilitation. The proposed method expands the possibilities of topsoil use, allowing the rehabilitation of slopes and embankments with native species
Mestrado
Biologia Vegetal
Mestre em Biologia Vegetal

The factors that influence the invasion of hillslopes by the shrub Pteronia incana in the communal rangelands of Ngqushwa (formerly Peddie) district were investigated. Mgwalana, one of the catchments in the district where encroachment by the species is widespread, was chosen. The study combined field observations with image analysis based on high resolution infrared imagery. The catchment was flown and high resolution infrared images (1mx1m) were taken using a Kodak DCS420 digital, colour-infrared camera. The images were analysed using Idrisi32 and Kilimanjaro GIS versions. The ability of different vegetation indices to separate P. incana from the other cover types was investigated. Field observations of the degree of P. incana invasion in relation to, inter alia, soil surface conditions, slope angle and visible forms of erosion were made. A Digital Elevation Model (DEM) of 20m spatial resolution was used to derive terrain parameters. The presence and absence of P. incana in relation to slope gradient and aspect were determined. The combined influence of the two terrain parameters and land use on the invasion was also investigated. The Topographic Wetness Index (WI), a component of the TOPMODEL was derived from the DEM and its relationship with the spatial distribution of P. incana was explored. Soil moisture dependencies for P. incana and grass species as well as surrogates for runoff under the shrub and adjacent bare areas were determined in the field. A high level of classification accuracy confirmed the reliability of digital camera imagery for spatial analyses. Distinct spectral separability for the surface vegetation cover types was achieved by means of the Perpendicular Vegetation Index (PVI) as opposed to the ratio based vegetation indices (NDVI, SAVI and MSAVI). The absence/presence of P. incana was noted to be strongly influenced by slope angle and aspect. The probability for P. incana occurrence increased with slope steepness and southerly slope orientation. Abandoned and grazing lands were identified as the main invasion hotspots. Blanket invasion of the former signified the high susceptibility of abandoned land to P. incana invasion. The combined influence of land use, slope gradient and aspect was also noted to have promoted the invasion. This is borne out by the concentration of the invasion on abandoned steep slopes with a southerly orientation. Local topographic variations were identified as having a strong bearing on P. incana spatial distribution. The topographically driven WI confirmed this relationship, such that P. incana was associated with the low WI values of convexities. Differences in the moisture dependencies between P. incana and grass species were demonstrated by the greater rooting depth of the former. During field surveys, soil surface crusting was noted as inherent to P. incana patchiness. The coupling between local topography and soil surface crusting underpins soil moisture variability at hillslope and patch scales respectively. This in turn determines the competition between P. incana and grass species and the eventual replacement of the latter by the former. A close spatial correlation between fully established P. incana and severe forms of soil erosion was observed. Loss of patchiness and expansion of inter-patch bare areas promote runoff connectivity erosion. As most of the runoff becomes run out, hillslopes tend towards dysfunctional systems. Greater soil moisture storage after rainstorms under P. incana tussocks than the adjacent bare areas signifies the shrub’s water harvesting capabilities. The tussocks could thus serve as a starting-pointbuilding- block for the rehabilitation of dysfunctional hillslope systems.

Tree-rings were analyzed to assess the relative importance of slope position and aspect as determinants of the climate-sensitivity of sugar maple and white oak radial growth. Tree size, crown condition, forest and soil composition, and site indices were assessed to document environmental differences between site-types and to verify similarity of stands within the same site-type. Climate-sensitivity was assessed using mean between-tree correlation, principal components analysis, mean sensitivity, regression analysis, and analysis of radial growth decline after severe drought. Ecological differences were found between high and low sites on north and south facing aspects. Sugar maple did not exhibit greater climate-sensitivity than white oak. Both species showed greater climate-sensitivity on upper and south-facing slopes.
Department of Biology

This thesis provides a description of the periglacial environment and features in the vicinity of Tiffindell Ski resort, on the slopes of Ben MacDhui (3001.2m.), the highest point of the East Cape Drakensberg, South Africa. Active and inactive periglacial features were located, mapped and described. Of particular interest were periglaciar slope deposits including gelifluction turf-banked lobes and stone lobes, and cryoturbation features including polygons and thufur. Local environmental factors, such as aspect, moisture, topography, soil texture and depth of freezing, appear to act as important controls on the spatial distribution of the periglacial features. Identification and quantification of periglacial processes in the regolith was investigated using temperature and soil moisture sensors coupled to dataloggers. Research was undertaken over a 16 month period from June 1995 to September 1996 so that comparisons between the winter conditions of 1995 and 1996 could be drawn. The Tiffindell area was observed to be characterised in the winter months by 'diurnal freezethaw days', as well as by 'ice days', 1996 experiencing colder temperatures than 1995. With more than 78% of the days from May to September 1996 being 'ice days', and simultaneously experiencing high soil moisture contents, freezing penetration to a depth of greater than 0.2m was observed to occur in the Tiffindell area, causing frost heave and gelifluction. The summer thaw of ice lenses that developed in the cold winter months caused surface movement downslope of gelifluction lobes of up to 39mm over an 18 month period, although movement declined rapidly with depth and was essentially restricted to the uppermost 130mm of the regolith. Other features such as sorted and non-sorted polygons and thufur were identified and found to be active under the present climatic conditions and depth of frost penetration at Tiffindell. Stone lobes were identified on the south and southeast-facing slopes at Tiffindell, but are apparently inactive under present climatic conditions. Their existence suggests the presence of severe seasonal frost in the past. The implications of the air and ground surface temperatures, and of seasonal frost penetration for the development of Tiffindell Ski resort were considered, and suggestions regarding their economic significance are presented.

Simulating the processes of rainfall and runoff are at the core of hydrologic modeling. Geomorphologic features, rainfall variability, soil types, and water table depths strongly influence hydrological process in Florida ecosystems. Topographic characteristics of the terrain define the stream paths and landscape. Alteration of these characteristics as a result of urban and/or agricultural developments, for example, can highly influence wetlands and river basin response. There are two predominant landforms in Florida: wetlands, where Variable Saturated Areas form near streams causing saturation excess runoff, and uplands where runoff is mainly generated by infiltration excess. The objective of this work is to analyze the impacts of geomorphologic and hydrologic characteristics on runoff mechanisms in humid environments such as Florida. In general, most research at the hillslope scale use hypothetical values of rainfall, sometimes non-realistic values, and single slope forms to explain the geomorphic and hydrologic process on Variable Saturated Areas. In this thesis, the complexity of hillslope processes on actual Florida topography is assessed by coupling a Digital Elevation Model with a two-dimensional variable saturated-unsaturated flow model called HYDRUS-2D. Actual rainfall records and soil parameters from the Characterization Data for Selected Florida Soils, Soil Survey were used to evaluate hydrologic impacts. A commercial software package, River Tools was used to display and extract topographic information from the Digital Elevation Models. Results show that when inflitration excess runoff is dominant, infiltration and runoff are very sensitive to time resolution, especially for convective storms. When saturation excess occurs, runoff is not affected by rainfall intensity. However, saturated hydraulic conductivity, depth to the water table, slope and curvature highly influence the extent of Variable Saturated Areas. Results indicate runoff in shallow water table environments is produced mainly by subsurface storm runoff, running below the surface, except in hillslopes with concave curvature and mild slopes. Additionally, concave hillslopes generate more saturation excess runoff than straight and convex hillslopes.

Lau Ka Wah Joyce.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (leaves 177-192).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgements --- p.iv
Table of Contents --- p.vi
List of Tables --- p.xi
List of Figures --- p.xiv
List of Plates --- p.xvi
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Introduction --- p.1
Chapter 1.1.1 --- Environment of Hong Kong --- p.1
Chapter 1.1.1.1 --- Topography --- p.1
Chapter 1.1.1.2 --- Climate --- p.1
Chapter 1.1.1.3 --- Expanding population --- p.3
Chapter 1.1.2 --- Landslide history in Hong Kong and government action --- p.4
Chapter 1.1.3 --- Slopes in Hong Kong --- p.6
Chapter 1.1.4 --- Stabilization means --- p.7
Chapter 1.2 --- Biotechnical stabilization --- p.8
Chapter 1.2.1 --- Concept --- p.8
Chapter 1.2.2 --- History --- p.9
Chapter 1.2.3 --- Advantages and strengths of vegetation --- p.9
Chapter 1.2.4 --- Other components in biotechnical stabilization --- p.11
Chapter 1.3 --- The situation in Hong Kong --- p.12
Chapter 1.3.1 --- Government policy on control of visual impact of slopes --- p.12
Chapter 1.3.2 --- Landslip Preventive Measures (LPM) Program --- p.15
Chapter 1.3.3 --- Slope landscaping proprietary systems --- p.16
Chapter 1.3.3.1 --- Proprietary systems --- p.16
Chapter 1.3.3.2 --- Problems and limitations --- p.20
Chapter 1.4 --- Ecosystem reconstruction on slopes --- p.23
Chapter 1.4.1 --- Concept --- p.23
Chapter 1.4.2 --- Plant requirements --- p.24
Chapter 1.4.3 --- Potential challenges --- p.24
Chapter 1.4.3.1 --- Steep gradient and related problems --- p.24
Chapter 1.4.3.2 --- Thin soil --- p.24
Chapter 1.4.3.3 --- Water supply --- p.26
Chapter 1.4.3.4 --- Nutrient availability --- p.27
Chapter 1.5 --- Species selection --- p.28
Chapter 1.5.1 --- Vegetation types --- p.28
Chapter 1.5.2 --- Natives or exotics --- p.29
Chapter 1.5.3 --- Currently employed species and problems --- p.29
Chapter 1.6 --- The current study --- p.31
Chapter 1.6.1 --- Objectives --- p.31
Chapter 1.6.2 --- Significance --- p.31
Chapter Chapter 2 --- Soil status and vegetation of cutslopes --- p.35
Chapter 2.1 --- Introduction --- p.35
Chapter 2.2 --- Materials and methods --- p.42
Chapter 2.2.1 --- Physical properties of substrates on slopes --- p.43
Chapter 2.2.1.1 --- Gradient --- p.43
Chapter 2.2.1.2 --- Aspect --- p.43
Chapter 2.2.1.3 --- Soil depth --- p.44
Chapter 2.2.1.4 --- Bulk density --- p.44
Chapter 2.2.1.5 --- Soil texture --- p.44
Chapter 2.2.2 --- Chemical properties of substrates on slopes --- p.45
Chapter 2.2.2.1 --- pH --- p.45
Chapter 2.2.2.2 --- Conductivity --- p.45
Chapter 2.2.2.3 --- Organic carbon --- p.46
Chapter 2.2.2.4 --- Carbon: nitrogen ratio --- p.46
Chapter 2.2.2.5 --- Total Kjeldahl Nitrogen --- p.46
Chapter 2.2.2.6 --- Mineral nitrogen (Ammonium and nitrate) --- p.46
Chapter 2.2.2.7 --- Total phosphorus --- p.47
Chapter 2.2.2.8 --- Available phosphorus --- p.47
Chapter 2.2.2.9 --- Major extractable cations --- p.47
Chapter 2.2.3 --- Statistical analysis --- p.47
Chapter 2.2.4 --- Other properties on slopes --- p.48
Chapter 2.2.4.1 --- Green coverage --- p.48
Chapter 2.2.4.2 --- Invaded species --- p.48
Chapter 2.3 --- Results --- p.48
Chapter 2.3.1 --- Physical properties of substrates on slopes --- p.48
Chapter 2.3.2 --- Chemical properties of substrates on slopes --- p.51
Chapter 2.3.3 --- Other properties of the slopes --- p.58
Chapter 2.3.3.1 --- Green coverage --- p.58
Chapter 2.3.3.2 --- Invaded species --- p.60
Chapter 2.4 --- Discussion --- p.61
Chapter 2.4.1 --- The physical properties of substrates on slopes --- p.63
Chapter 2.4.2 --- Chemical properties of substrates and their seasonal changes on slopes --- p.66
Chapter 2.4.3 --- Green coverage and its seasonal changes --- p.70
Chapter 2.4.4 --- Comparison between the standards and results --- p.75
Chapter 2.4.5 --- Other problems --- p.78
Chapter 2.5 --- Summary --- p.79
Chapter Chapter 3 --- Species selection for cutslope revegetation --- p.81
Chapter 3.1 --- Introduction --- p.81
Chapter 3.1.1 --- The need to expand species variety for revegetation --- p.81
Chapter 3.1.2 --- Criteria for plant selection --- p.81
Chapter 3.1.3 --- Advantages of grasses and herbaceous legumes --- p.83
Chapter 3.1.4 --- Pot experiment --- p.85
Chapter 3.2 --- Materials and methods --- p.86
Chapter 3.2.1 --- Summer grasses --- p.88
Chapter 3.2.1.1 --- Germination rate --- p.88
Chapter 3.2.1.2 --- Pot experiment --- p.88
Chapter 3.2.2 --- Summer legumes --- p.90
Chapter 3.2.3 --- Winter grasses --- p.90
Chapter 3.2.4 --- Winter legumes --- p.90
Chapter 3.3 --- Results --- p.91
Chapter 3.3.1 --- Soil properties --- p.91
Chapter 3.3.2 --- Aboveground biomass production --- p.91
Chapter 3.3.2.1 --- Summer grasses --- p.91
Chapter 3.3.2.2 --- Summer legumes --- p.98
Chapter 3.3.2.3 --- Winter grasses --- p.101
Chapter 3.3.2.4 --- Winter legumes --- p.106
Chapter 3.3.3 --- Foliar nutrient concentration --- p.111
Chapter 3.3.3.1 --- Summer grass --- p.111
Chapter 3.3.3.2 --- Summer legumes --- p.113
Chapter 3.3.3.3 --- Winter grasses --- p.114
Chapter 3.3.3.4 --- Winter legumes --- p.115
Chapter 3.4 --- Discussion --- p.116
Chapter 3.4.1 --- Aboveground biomass production --- p.119
Chapter 3.4.1.1 --- Summer grasses --- p.119
Chapter 3.4.1.2 --- Summer legumes --- p.121
Chapter 3.4.1.3 --- Winter grasses --- p.122
Chapter 3.4.1.4 --- Winter legumes --- p.125
Chapter 3.4.2 --- Foliar nutrient concentration --- p.126
Chapter 3.4.3 --- Common nutrient application and the plant requirements --- p.128
Chapter 3.5 --- Summary --- p.129
Chapter Chapter 4 --- Growth of summer grasses in a combination of stresses --- p.131
Chapter 4.1 --- Introduction --- p.131
Chapter 4.2 --- Materials and methods --- p.131
Chapter 4.2.1 --- Study species --- p.131
Chapter 4.2.2 --- Pot experiment --- p.132
Chapter 4.3 --- Results --- p.132
Chapter 4.3.1 --- Pot experiment --- p.132
Chapter 4.3.1.1 --- Aboveground biomass --- p.132
Chapter 4.3.1.2 --- Foliar nutrient concentration --- p.138
Chapter 4.4 --- Discussion --- p.140
Chapter 4.4.1 --- Pot experiment --- p.140
Chapter 4.4.1.1 --- Aboveground biomass --- p.140
Chapter 4.4.1.2 --- Foliar nutrient concentration --- p.141
Chapter 4.5 --- Summary --- p.141
Chapter Chapter 5 --- Growth of summer grasses on simulated slopes --- p.143
Chapter 5.1 --- Introduction --- p.143
Chapter 5.2 --- Materials and methods --- p.145
Chapter 5.2.1 --- Study species --- p.145
Chapter 5.2.2 --- Artificial panel trial --- p.145
Chapter 5.2.2.1 --- Experimental setup --- p.145
Chapter 5.2.2.2 --- Growth pattern and green coverage --- p.147
Chapter 5.2.2.3 --- Sediment runoff and change in soil thickness --- p.147
Chapter 5.3 --- Results --- p.148
Chapter 5.3.1 --- Grass growth on artificial panels --- p.148
Chapter 5.3.1.1 --- Aboveground biomass and green coverage --- p.148
Chapter 5.3.2 --- "Relationship between rainfall, runoff and soil loss" --- p.149
Chapter 5.3.2.1 --- Effect of rainfall on runoff --- p.149
Chapter 5.3.2.2 --- Effect of runoff on soil loss --- p.151
Chapter 5.3.2.3 --- Effect of rainfall on soil loss --- p.152
Chapter 5.3.2.4 --- Effect of aspect --- p.154
Chapter 5.3.2.5 --- Effect of green coverage on soil loss --- p.154
Chapter 5.3.3 --- Percentage of greening --- p.155
Chapter 5.3.4 --- Soil thickness --- p.157
Chapter 5.4 --- Discussion --- p.159
Chapter 5.4.1 --- Grass growth on artificial panels --- p.159
Chapter 5.4.2 --- "Relationship between rainfall, runoff and soil loss" --- p.160
Chapter 5.4.2.1 --- Effect of rainfall on runoff --- p.160
Chapter 5.4.2.2 --- Effect of runoff on soil loss --- p.160
Chapter 5.4.2.3 --- Effect of rainfall on soil loss --- p.161
Chapter 5.4.2.4 --- Effect of aspect on runoff and soil loss --- p.163
Chapter 5.4.2.5 --- Effect of green coverage on runoff and soil loss --- p.164
Chapter 5.4.3 --- Effects of other variables --- p.165
Chapter 5.4.3.1 --- Effect of green coverage --- p.165
Chapter 5.4.3.2 --- Effect of aspect --- p.167
Chapter 5.4.4 --- Soil thickness --- p.168
Chapter 5.5 --- Summary --- p.168
Chapter Chapter 6 --- Conclusion --- p.170
Chapter 6.1 --- Summary of major finding --- p.170
Chapter 6.2 --- Implications of the study --- p.172
Chapter 6.2.1 --- Growth medium --- p.172
Chapter 6.2.2 --- Species selection --- p.174
Chapter 6.3 --- Limitations of the study --- p.175
Chapter 6.4 --- Suggestions for further investigation --- p.175
References --- p.177

Advances in hillslope hydrology have been numerous in the past two decades. However many of these advances have been highly site specific in nature, without identifying any means of linking processes across different spatial scales. Meaningful Prediction in Ungauged Basins (PUB) requires the understanding and observation of processes across a range of scales in order to draw out typical hydrological controls. Contempory tracer based methods of quantifying a combination of hillslope processes have identified hillslope geology as the main determinant in different catchment response types. A range of hillslope scale models have been developed in the last 20 years, using different levels of detail to simulate hillslope hydrological responses. Often the data heavy requirements of hillslope scale models make them impractical to apply at larger scales. While catchment scale models lack the ability to represent hillslope scale processes. In order to overcome this, a scale applicable model with the ability to represent hillslope and catchment dynamics is required to accurately quantify hillslope and catchment hydrological processes. This study aims to characterize typical hillslope soil type responses through inferring qualitative hillslope descriptions into a numerical catchment scale model allowing for lateral subsurface routing between adjacent soil horizons. Hydrometric and tracer observation are used to describe and quantify dominant hillslope hydrological processes. Simplifications of hillslope process descriptions are used to calibrate the model to represent the subsurface hillslope connectivity. Results show that hillslope scale hydrological process characteristics can be faithfully simulated with quaternary scale climate, land use and soils data, discriminating only between different hillslope soil types. The simplification of hillslope soils into three distinct groups allows for the further derivation of dimensionless descriptors of hillslope hydrological response using the Advection Dispersion Function. Slopes with shallower stratified soils showed rapid responses to rainfall in the soil water, while those with deeper soils and less horizontal stratification showed appreciably slower responses to rainfall, with older hillslope water dominating soil water for longer periods. This identifies soils as a dominant determinant in hillslope runoff characteristics. This allows for the characterization and ultimately a simplified classification of different hillslope soils and their response types, which is applicable at a range of scales.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Terracettes are a widely occurring form of micro-relief found throughout regions displaying various climatic and environmental conditions. Much speculation surrounds the processes responsible for their formation and development. An investigation of these micro-forms, their associated soil physical properties, sustaining mechanisms, and their relationship to slope stability was undertaken in Giant's Castle Game Reserve, KwaZulu - Natal Drakensberg, South Africa. The study showed that relationships between terracette morphology and soil physical properties within the Reserve are few, and that current soil conditions cannot be used to infer process related to terracette formation. However dry bulk density data indicated that soil creep is the dominant formative mechanism within the Reserve. Throughflow at riser surfaces was the dominant sustaining mechanism, with needle ice growth, wind, surfacewash and animal disturbance contributing minor retreat at both treads and risers. Aspect played an important role in determining soil physical characteristics. It was inferred that terracettes imparted stability to the slopes on which they are found, and with continued retreat at both treads and risers the slope was again placed under conditions of instability.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

Previous studies found that during a rainfall event, pre-event water, which exists in the catchment before the event, may appear in significant amounts in the stream stormflow hydrograph. Pre-event water is predominantly groundwater. Among the mechanisms that have been proposed to explain the rapid mobilization of pre-event water from hillslopes are: (1) groundwater ridging (GWR) i.e. the rapid rise of a water table in environments, where the capillary fringe, or the zone of tension saturation, is very close to the ground surface and (2) the Lisse Effect (LE) i.e. the rapid response of a groundwater level to pressurized pore air in the unsaturated zone. Published literature explains that GWR is caused by the application of a small amount of water on the ground surface. On the LE, it is explained that pressurized pore air acts at the water table, resulting in a rapid rise of the water level in a well, screened below the water table. These explanations are insufficient on the physical processes involved in GWR and the LE. The objectives of this study were: (1) to use the commonly observed catchment hydrological processes i.e. tensiometric pore water pressure, shallow groundwater levels, rainfall data and the hydraulic properties of soils, to quantify and describe the physical processes involved in GWR and the LE mechanisms; (2) to perform laboratory experiments, in order to understand the physical processes involved in the LE; and (3) to develop a mathematical theory that can describe the physical processes in the LE. Results indicated that GWR and the LE are caused by the addition (elevation) of potential energy in water within the capillary fringe. In GWR, the additional energy is from the intense rainfall. In the LE, the additional energy is from compressed pore air in the unsaturated zone. In both mechanisms, the added energy diffuses through the capillary fringe, as a downward pressure wave, releasing the tension forces in water. As soon as the downward pressure wave-front arrives at the water table, the water table begins to ascend, as an upward pressure wave. The ascending water table steepens the hydraulic gradient, which results in the rapid groundwater fluxes, without the recharge of the water table by the infiltration profile.
Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2013.

Several hydrological studies claim that available water resources in a catchment are affected by large scale afforestation, especially where the regional rainfall is considered marginal for the support of silviculture. Nevertheless, the mechanisms and magnitude of the perturbations to the receiving water resources due to afforestation are still not clearly understood. To improve this understanding an intensive hydrological experiment has been initiated in the small grassed Weatherly catchment of the Mondi, North East Cape Forests. Details of the soil water dynamics on the Molteno formations in the catchment have been be studied. This research presents a description and first results of the establishment of an experiment which comprises monitoring the water budget of the grassed catchment prior to the afforestation of the catchment to plantations of exotic trees. The studies currently include, monitoring the infiltration and redistribution of soil water on a hillslope as well as monitoring of interflow mechanisms and localised mechanisms of soil water accumulation influenced by the topography and geology of the catchment. In addition to the intensive soil water monitoring, specific experimentation has been conducted at various locations on the hillslope. These comprise macropore flow process studies and 2-dimensional tracer experiments. Details of these experiments as well as the automated soil water and groundwater monitoring instrumentation are presented. An intensive soil survey on a 30 m x 30 m grid as well as a comprehensive measurement strategy of soil physical and hydraulic properties are highlighted. A review of 2-dimensional numerical hillslope soil water process models is also presented. Results from this research show that on hillslopes underlain by Molteno sandstones localised perched water tables form. These water bodies, upon reaching a critical height above the bedrock cascade downslope as interflow recharging the water bodies downslope. The response to infiltration increases downslope and in the toe region interflow occurs readily in response to rainfall compared to the midslope where substantial rain needs to infiltrate.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.

Hillslope mechanisms and processes are a complex and dynamic set of interactions, but are nevertheless vital components of hydrology due to their critical interactions with surface and groundwater (Lorentz, 2001a). In order to observe and quantify these flow generating mechanisms, the Weatherley subcatchment was selected where the components of streamflow generation have been studied and can be quantified separately. Surface, shallow subsurface and the deeper groundwater interactions are particularly important when quantifying runoff generation from within hillslope, riparian and wetland zones as they are the dominant runoff generating zones within the Weatherley catchment. These components of flow are important to quantify for the further study of flow generation mechanisms, their dynamics and fluxes at the hillslope and small catchment scale, low flow contributions, climate change as well as the consequences of land use change (Lorentz, 2001b). Transfer functions were found to be the best adaptation of hydrograph separation for distributed hydrological modelling purposes when attempting to quantify the various streamflow hydrograph components. In this study, the runoff components were simulated along transects using the HYDRUS-2D model, where the simulated soil water dynamics are compared with the observed tensions and water contents at different depths within the soil profile in order to quantify the contributing hillslope fluxes to streamflow generation. The 2001 data set was used with the rainfall and potential evapotranspiration data being converted into rates according to the breakpoint rainfall data. The HYDRUS-2D modelling exercise is performed to calculate the variety of flux rates (timing and quantities) within the subcatchment, so that the overall stream hydrograph can be properly deduced when modelling this catchment with transfer functions in the future. An understanding of the driving forces as well as the behaviour of sources and flow paths was extracted from this thesis, along with gaining some knowledge about the mechanisms and behaviour of streamflow generating mechanisms at the hillslope and small catchment scale. Troch et al (2003) clearly encapsulates the essence of modern day catchment hydrology in stating that hillslope response to rainfall remains one of the most central problems of catchment hydrology in order to quantify catchment responses. The processes whereby rainfall becomes runoff continue to be difficult to quantify and conceptualise (Uhlenbrook et al., 2003) and this is because the characterisation of subsurface water flow components is one of the most complex and challenging tasks in the study of the hydrologic cycle (Achet et al., 2002). Since trying to understand the temporal and spatial variability of moisture content and the subsurface flow mechanisms is a complicated problem (Achet et al., 2002), an attempt is made in this thesis to gain insights into the temporal and spatial variability of soil tensions and soil moisture content at various depths on hillslope transects by combining modelling exercises with field observations. From this modelling, the hillslope water balance and contributing fluxes are derived in effort to augment, at a later stage, the hillslope response functions.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.