Thesis (M.S.)--Rhodes University, 2004. / Title from PDF t.p. (viewed on Apr. 30, 2006). Includes bibliographical reference (p. 171-182).

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references (leaves 104-108). Online version available on the World Wide Web.

Landslides are relatively frequent in Ottawa due to the presence of sensitive marine clays (Leda clay or Champlain Sea clay), and the presence of natural or climatic triggers such as rainfall or snowmelt. A geographic information system (GIS) based modeling tool has been developed to assess and predict climate (rainfall and snowmelt)-induced landslides in the sensitive marine clays of the Ottawa region. The Transient Rainfall Infiltration and Grid-based Regional Slope-Stability (TRIGRS) model is used in a GIS framework to investigate the influence of rainfall and snowmelt on shallow landslides through the Ottawa region, with respect to time and location. First, the GIS and TRIGRS models are combined to assess landslide susceptibility with respect to rainfall. The GIS-TRIGRS approach requires topographic, geologic, hydrologic, and geotechnical information of the study area. In addition to this technical information (input data), rainfall intensity data for different durations (5 minutes, and 6, 12, 18, and 24 hours), and historical data of the regional landslides is required. This data is used to verify the locations of predicted landslide-susceptible areas with respect to historical landslide maps in the area. The generated results from the GIS-TRIGRS model were verified by comparing the predicted and historical locations of shallow landslides induced by rainfall throughout the Ottawa region. The comparison results showed a high correlation between the predicted areas of landslides and the previously reported landslides. In addition, the results also indicated that not all previous landslides in Leda clays were triggered by rainfall. The second application of the developed GIS-TRIGRS approach was used to assess and predict snowmelt-induced landslides in areas of sensitive marine clay in the Ottawa region. Similar to the first analysis, the approach requires the following input data: topographic, geologic, hydrologic, geotechnical, snowmelt intensity data for various periods (6–48 hours, 3–15 days, 25 days, and 30 days), This approach also requires data indicating the location of historical landslides in the study area. Using this data, we examine both the timing and location of shallow landslides due to snowmelt in a GIS-based framework. The developed model was validated by comparing the predicted landslide-susceptible areas to historical landslide maps in the study area. A high correlation between predicted and historical landslide location trends was obtained, confirming that the developed GIS-TRIGRS model can predict the snowmelt-induced landslide susceptibility in the sensitive marine clays relatively well. The model results reinforced the conclusion that areas with high slopes and sensitive marine clays were more prone to snowmelt-induced landslides. Finally, in a Geographic Information System (GIS) the landslide occurrence susceptibility in the Ottawa area was modeled. Results of such models are presented as maps showing landslide susceptibility in Champlain Sea clays (Leda clays) in the Ottawa area due to both rainfall and snowmelt. Various input data was collected and entered into a GIS and TRIGRS model. The main categories of such inputs are climate, topography, geology, hydrology, and geotechnical data. The rainfall and snowmelt intensity data was extracted for 24 to 48 hour periods from Environment and Climate Change Canada historical climate records. Thereafter, the factor of safety was calculated in order to determine the stability of slopes across the study area. The model assesses the effects of rainfall and snowmelt on landslide occurrence, and based on the calculated factor of safety at each pixel of the study area, the model calculates the landslide susceptibility. The results presented in this thesis will provide a geotechnical basis for making appropriate engineering decisions during slope management and land use planning in the Ottawa region.

The objective of the thesis is to make a critical assessment of the performance of three relatively simple deterministic models of the rainfall-runoff process. The need to evaluate and compare deterministic models arises because of the large number of models which are available in the literature. A number of the available models would appear to be equally suitable for a given situation whereas many models are found to be valid only under the specific range of conditions for which they were developed. Therefore there is a need for guidelines to allow the most judicious selection of a model for a particular set of circumstances. The models used in the study will be tested in a semi-arid catchment to determine their applicability under ephemeral flow conditions

No description available.

This study gives a phenomenologically based stochastic model of space -time rainfall. Specifically, two random variables on the spatial rainfall, e.g. the cumulative rainfall within a season and the maximum cumulative rainfall per rainfall event within a season are considered. An approach is given to determine the cumulative distribution function (c.d.f.) of the cumulative rainfall per event, based on a particular random structure of space -time rainfall. Then the first two moments of the cumulative seasonal rainfall are derived based on a stochastic dependence between the cumulative rainfall per event and the number of rainfall events within a season. This stochastic dependence is important in the context of the spatial rainfall process. A theorem is then proved on the rate of convergence of the exact c.d.f. of the seasonal cumulative rainfall up to the ith year, i > 1, to its limiting c.d.f. Use of the limiting c.d.f. of the maximum cumulative rainfall per rainfall event up to the ith year within a season is given in the context of determination of the 'design rainfall'. Such information is useful in the design of hydraulic structures. Special mathematical applications of the general theory are developed from a combination of empirical and phenomenological based assumptions. A numerical application of this approach is demonstrated on the Atterbury watershed in the Southwestern United States.

The primary focus of this thesis is to describe the prevailing atmospheric conditions when heavy rainfall occurs over the Gauteng Province in South Africa. This thesis first describes the characteristics of daily heavy rainfall over Gauteng by defining different heavy rainfall classes and considering the seasonal distribution of these events. Late summer (January, February and March) has considerably more heavy rainfall days than early summer. The change of the character of the atmosphere as the summer season progresses is highlighted by the investigation into the monthly average synoptic circulation patterns when heavy rainfall occurs. The weather systems change from extra-tropical in the first few months of the summer rainfall season to tropical in February months. It is also shown how cyclonic vorticity advection occurs in the upper troposphere whenever heavy rainfall occurs, irrespective of the time of the season. A deep layer of horizontal wind convergence is also present when heavy rainfall occurs and this is replaced by horizontal wind divergence above that. A monthly climatology of sounding-derived parameters associated with heavy rainfall is constructed and it is again apparent how the atmosphere changes from one where conditional instability dominates the production of heavy rainfall in early summer to one where convective instability plays a dominant role in late summer. Twelve sounding-derived variables are identified to describe the thermodynamical profile of the atmosphere when heavy rainfall occurs over Gauteng. They include variables not previously used such as the Elevated K-Index and the meridionial wind component near the surface. Self-organizing maps are used to create a climatology of the vertical profile of the atmosphere during heavy rainfall and this methods captures the changes to the atmospheric state during the progression of the summer season. Favourable sounding-derived parameters and circulation criteria are combined in a self-organizing map to predict daily rainfall frequencies. This method produces encouraging results and methods should be explored to create probabilistic daily rainfall forecast for Gauteng in an operational environment. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Geography, Geoinformatics and Meteorology / unrestricted

This thesis examines the climatic trends of rainfall and temperature in Uganda using historical data. And because climate is an important aspect in water resources management and livelihoods formation, an attempt to explain how the interaction impacts on the two is made in the context of climate variability and change. The assumption is that climate change/variability has had an effect on water resources management and the way individual, households and society at large form livelihoods in Uganda. The rationale for the investigation is the number of climate and livelihood related studies that have been undertaken for Uganda over recent years, which have not focused specifically on the water resources management and livelihood formation. The study is grounded by reviewing the theoretical perspectives of climate science which underpin the concepts of climate change, climate variability and impacts on livelihoods in the world, tropics, Africa, east Africa and Uganda in that order. A cross sectional research design based on selected case studies from sub-counties located in the main sub-basins across the country is used. Both qualitative and quantitative data analysis techniques are applied independently or in combination on climatic data from Uganda‟s Department of Meteorology, data generated from field interviews and landsat images. The data sets are analysed using MS EXCEL, SPSS, MATLAB, ANCLIM, TREND TOOL, GIS and ENVI 4.8 to establish climatic trends and deduce evidence of change and variability. The impact on livelihood formation is investigated through the assets available to the households using the DFID framework. The study therefore has investigated the characteristics of climate in Uganda especially by following up on the responses that arose from the field study. Through their own observations, respondents noticed changes in temperature and rainfall. Temperature variables like diurnal temperature range, maximum and minimum temperatures and rainfall (monthly, seasonal, annual) have been investigated, to establish whether these observations were impacting on livelihood formations and water resources which are central in the wellbeing of individual households. Results show decadal variability of rainfall with marked seasonal cycles, temporal variability of drought patterns is detected; variations in annual rainfall are low with no significant trends observed in the main drainage sub-basins. Significant trends occur in October, November, December and January. A noticeable decrease in the annual total rainfall was observed mostly in north-western and south-western sub-basins. Rainfall trend in the second normal of June-July-August (JJA) is decreasing in all the main drainage sub-basins; highest rainfall was recorded in April, while January, June and July have the lowest rainfall. Spatial analysis results show that stations close to Lake Victoria recorded high amounts of rainfall. Average annual coefficient of variability was 19% signifying low variability. Rainfall distribution is bi-modal with maximums experienced in March- April- May and September- October- November seasons of the year. PCI values show a moderate to seasonal rainfall distribution. FNW Nsubuga – University of Pretoria Page 11 Spectral analyses of the time components reveal the existence of a major period around 3, 6 and 10 years. Intra-annual temperature show reduced variability over recent decades, which is not statistically significant. Maximum temperatures are more variable compared to minimum temperatures in Uganda. An increasing trend in hot days, hot nights, warm nights and warm spells are also detected. At seven of the stations, annual temperature range and diurnal temperature range trends are negative. The finding that intra-annual and intra-monthly variance is declining suggests that fewer anomalously extreme temperature episodes occur. The gap between maximum and minimum extremes is reducing, which supports the observation that minimum temperatures are on the increase. At a micro-level analysis using Namulonge as a case study, total rainfall in March-May season decreased, while maximum temperatures increased between April and September, with statistically significant trends at 5% confidence level. The Mann-Kendall test revealed that the number of wet days reduced significantly. Temperatures are warmer and rainfall higher in the first climate normal compared to the recent 30 years. Direct rainfall, which is the most important source of water for water resources, recently, is experiencing variability, which is threatening the distribution of water resources in Uganda. The characteristics, availability, demand and importance of present day water resources in Uganda as well as the various issues, and challenges pertaining to management of water resources of the country are established. The present analysis reveals that surface-water area fluctuation is linked to rainfall variability. In particular, Lake Kyoga basin lakes experienced an increase in surface-water area in 2010 compared to 1986. This work has important implications to water resources management and people whose livelihoods depend on natural resources especially in this era of climate change. Evidence from the field survey validates what data analysis reveals from historical data. Respondents from the field study are aware of climate change, had noticed some changes in climatic variables and were adapting by changing lifestyle and diversifying to activities that are less prone to weather. Livelihoods in Uganda have evolved based on the availability of opportunity afforded by the natural resources base including water resources. / Thesis (PhD)--University of Pretoria, 2013. / gm2014 / Geography, Geoinformatics and Meteorology / unrestricted

MESHWR / Department of Hydrology and Water Resources Management / This research was aimed at determining the impact of rainfall events on suspended sediment concentration (SSC) and water quality and links to sediment management in Dzindi River Catchment, Limpopo Province. Rainfall events of different magnitudes and duration erode different sediment volumes resulting in significant variation in sediment loads of receiving water bodies. This affects the water quality of such water bodies. Water samples for water quality and suspended sediment measurements were collected after each rainfall event for periods of six and five months, respectively, in two consecutive rainy seasons. The periods were from October 2012 to March 2013 and December 2013 to April 2014. The samples were collected from selected cross-sections at four sites along Dzindi River. Physical water quality parameters or water quality indicators (pH, Electrical conductivity (EC) and turbidity) were measured with multi 340i/set multimeter and Orion Aqua Fast II turbidity meter, as they are the indicators of the overall status of the water quality. Suspended sediment concentration (SSC) for each sample was measured using evaporation method. SSC at each cross section was computed using the mean discharge-weighted formula. Field survey was undertaken to identify land use activities that promote erosion and hence sedimentation. The relationship between SSC and rainfall magnitude was determined using sediment rating curves. Water quality and sedimentation status at each cross-section together with the information from the GIS map aided in identifying and recommending the best sediment management strategies for different sites in the study area. pH values for October 2012 to March 2013 and December 2013 to April 2014 were both higher in the downstream site of the river catchment, which is Manamani site. Lowest pH was found in the upstream and mid-stream sites, which were Dzindi water treatment works (DWTW) and Tshisaulu, respectively. Tshisaulu had highest EC value and Lwandani had lowest value, respectively, for the period of October 2012 to March 2013. DWTW had the highest EC value and Tshisaulu had the lowest EC value, respectively, for the period of December 2013 to April 2014. Manamani had high turbidity value and Lwandani had low turbidity value for October 2012 to March 2013. Turbidity for DWTW for the period of December 2013 to April 2014 was the highest and Tshisaulu had the lowest turbidity value. Sediment rating curves for DWTW, Tshisaulu and Manamani, respectively, had coefficient of determination (R2) values of 0.185, 0.53 and 0.99, respectively. Different sediment management strategies, including slope and bank protection and minimum and mulch tillage, were recommended based on topography and land use activities and these strategies can prevent soil erosion and minimize transport of sediments into the river.

Vegetation in semi-arid regions is subject to change when heavily utilised by herbivores. Changes in species richness, species and growth form composition, total cover and plant palatability in response to rest (fenced) and grazing (open) treatments was investigated in Sanbona Wildlife Reserve over five years (2004-2008). This reserve is over 55 000 ha and has four dominant vegetation types: Little Karoo Quartz Vygieveld, Western Little Karoo, Montagu Shale Renosterveld and previously transformed Renosterveld classified here as Old Lands. There was no significant change in vegetation dynamics between the fenced or open plots. There were significant differences between years in some vegetation types. All vegetation types showed both treatments having similar shifts in floristic composition. Floristic composition deviated the greatest in 2008 in all vegetation types. This was attributed to an increase in summer and winter rainfall in 2008, as all plots were similarly affected. There was no observed impact of herbivores although disturbance from small rodents and baboons was observed in a few plots. The lack of detectable difference between the fenced and open sites was attributed to low stocking rates, good rainfall and insufficient time.