Subsequent to the impounding of the Pongolo river in the 1970's, development of irrigated agriculture on the Makatini flats has been reducing the area of vegetation available for grazing, and flooding patterns on the seasonally inundated Pongolo River Floodplain have been determined by the controlled release of water from the Pongolapoort dam. About 50 000 people live along the 10 000 ha floodplain within the 63 000 ha northern region of the flats which was studied. This population includes 2 970 registered cattle owners who own a total of 19 300 cattle. The objectives of this study were: to gain an understanding of the Makatini pastoral system which would facilitate prediction of the effects of potential developments, including agricultural expansion, modification of floodplain hydrology and changed cattle management practices on the utility value of cattle; and to provide guidelines for the management of pastoral resources on the Makatini and other traditional African pastoral systems. It was established that the value of cattle cannot be determined without understanding the importance of the subsistence utilities provided and that the value of utilities relative to each other influences the way in which the system is stocked and managed by the local people. The value of all marketed and non-marketed utilities was determined and the implications of the economic evaluation for the identification of management options in African pastoral systems assessed. Despite the "low productivity" of the Makatini system compared to western style ranches, cattle owners receive annual returns worth approximately 100 % of the asset value of their stock. This explains low market offtake rate in this and other subsistence systems. Non-marketed utilities, particularly milk production provide most of the returns to cattle owners. The mean stocking density on the floodplain vegetation was estimated to be three times that of dry-land areas, but only 23 % of all grazing time is spent on the floodplain. Although floodplain forage provides an important supplement to winter grazing, its use is not vital to maintenance of animal condition. The coincident occurrence of an annual "stress period"; greater acceptability of Echinochloa pyramidalis vegetation as forage; the absence of floods; and the reduced use of floodplain fields, results in increased floodplain use in winter to a stocking density approximately ten times that of dry-land areas. How the floodplain hydrology, rainfall and grazing interact with the crop growth rate and quality of E. pyramidalis stands was examined. The forage production potential of E. pyramidalis was found to be higher than that of other floodplain vegetation types and stocking densities of up to 4.5 AU/ha in summer and 2.5 AU/ha in winter are considered possible on the Pongolo floodplain. Echinochloa pastures may become wet and cause scouring if grazed exclusively, but grazing reduces plant moisture content and makes the forage more acceptable. Local pastoral management was found to depend on the collective activities of cattle owners in pursuit of personal needs in a dynamic socio-economic context. Motivation for the manipulation of cattle numbers and herd composition is dictated by a cattle owner's perception of his needs for utilities and his ability to access those benefits. Because of this, the pastoral practices were found to be closely linked to other socio-economic activities such as agriculture and migrant labour. stock owners have a narrow perspective of pastoral resource management and use strategies developed on small spatial and temporal scales. In contrast development planners tend to identify objectives on a regional scale and on long-term (10 - 50 year) time scales and to orient management towards maximising the value of marketable utilities and preventing long-term overstocking. Management of pastoral resources in traditional African systems requires that the needs of local people be met, that the resource base be maintained; that pastoral policy be developed as a component of regional development planning and that close liaison between interest groups be maintained. Failure to establish or maintain this liaison is considered the main reason for the failure of many African pastoral development programmes. It was recommended that local pasture management committees be established on the Makatini and that extension officers, trained specifically to understand management problems of Third World pastoral systems, be used to maintain liaison between stock owners and development planners. It was also suggested that formal cattle camps be established and managed by local people and that at least one flood (river flow> 200 cumecs) be released from the Pongolapoort darn each summer. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1988.

A social survey of the communities living adjacent to the Pongolo river floodplain was carried out, in order to understand the perceptions of the impact of artificial flood releases on the general use of natural resources of Pongolo floodplain in terms of: general resource use, stream flow, water quality and subsistence agriculture. The results show that floodplain communities perceive that the present artificial flood releases which are intended to maintain the environmental requirements of the floodplain are not meeting their needs nor the needs of the environment. Key perceptions on environmental impacts identified are: (i) reduction in water required to maintain floodplain resources, (ii) deterioration in water quality and (iii) decrease in available floodplain land and natural resources. / Thesis (M.Env.Dev.) - University of KwaZulu-Natal, Pietermaritzburg, 2007.

The impounding of the waters of the Pongolo river, upstream of its floodplain on the Mocambique coastal plain, may adversely affect the functioning of the floodplain system. A multidisciplinary study of the functioning of the floodplain was initiated to provide a basis for the development of a management strategy for the floodplain. The study reported in this dissertation considered the flood dependence and functioning of the vegetation of the seasonally inundated area. The vegetation was mapped and the communities ordinated, according to the Braun-Blanquet technique, in relation to their positions relative to high flood level (HFL) and the level of the water after flood subsidence (i.e. maximum retention level, MRL). Community distribution was shown to be strictly determined by both the height of the floods and by the MRL. It was concluded that periodic floods are essential for the maintenance of the communities. The Cynodon dactylon (L.) Pers. Community, which forms extensive meadows in the zone of periodic inundation, was studied in detail. As the water level receded during winter, productivity was high (up to 23 kg ha¯¹ d¯¹1 dry mass) and a palatable sward was produced. This is heavily grazed by domestic stock, but as the soil dries out and water stress becomes significant, production decreases, C. dactylon becomes less palatable, and grazing shifts to newly exposed areas. The shift in grazing allows the build up of a large standing crop of both grazeable and ungrazeable (below ground and stolons) material. At the time of inundation by the next floods c. 910 kg ha¯¹ of dry mass, c. 17 kg ha¯¹ nitrogen and c. 2 kg ha¯¹ phosphorus have been removed by grazers. It is concluded that this production, which is flood dependent, forms an important supplement to stock grazing during winter. It is suggested that this source of grazing could be stimulated by irrigation during winter. Cynodon dactylon is shown to decompose rapidly during inundation, losing half of its mass and nutrients in c . 28 days. It therefore represents a major energy and nutrient input during the aquatic phase. The extent to which it is grazed during submergence is unknown. The nutrient input is derived ultimately from the soils of the inundated areas and, since nutrients are being removed by both terrestrial grazers and flushing, continued production is reliant upon the annual sediment load reaching the floodplain. Most of the sediment load will now be deposited in the impoundment, and fertilization may be necessary to maintain productivity. The response of C. dactylon to the seasonal fluctuations in water level are used to formulate proposals for water release from the dam. These include proposals for the short-term, i.e. until the demand for irrigation water conflicts with the requirements of the floodplain, and for the long-term, when less water will be available for the floodplain / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1981.

<p> The stratigraphy of the Pleistocene sediments of the Credit Valley of Ontario embraces two large fining-upwards sequences which correspond to the deposition of glacial debris during the retreat of the last two glacial periods in south central Ontario. The fining-upwards sequences have a basal gravel unit, a middle cross-stratified sand unit, and an upper unit containing small coarsening-upward sequences. All three of these sedimentary units are the result of deposition of sediment in a braided fluvial system. The basal gravel unit displays mid-channel gravel bars and side channel deposits. The cross-bedded sand unit exhibits incised bed-form deposits such as linguoid bars, dunes and ripples. The upper unit of coarsening-upwards sequences (which in places are interbedded with the cross-stratified sand facies) represents the deposits of bank overflow and consequent reactivation of unused channels on the braided river floodplain.</p> <p> During the Halton and Wentworth ice advances, till was deposited on the surrounding plain. With retreat of the ice masses, meltwater and outwash debris built up an alluvial plain in the lower and wider reaches of the Credit Valley near Glen Williams. These alluvial plains or sandurs were built up by deposition from braided streams. Outwash from the Halton Ice built a sandur plain on top of one constructed in Wentworth time. Post glacial drainage has incised these glaciofluvial deposits and leaves them exposed along the banks of the present Credit River. </p> / Thesis / Master of Science (MSc)

River-floodplain connectivity is the degree of water-driven transport of matter, energy, and organisms between rivers and their floodplains. Recent advancement of high-resolution lidar data and numerical modeling is helpful to explore river-floodplain connectivity precisely to improve our predictions of sediment transport and deposition on floodplains. In the present work, we studied floodplain sediment transport and deposition, and juvenile mussel settling in three river systems in the US. A two-dimensional hydrodynamic model was developed and simulated model results were coupled with field measurements to study river-floodplain systems of the East Fork White River in Indiana, South River in Virginia, and Dan River in North Carolina. Results show that the East Fork White River in Indiana is capable of supplying sand to the channels on the floodplain and these floodplain channels can transport sand in suspension and gravel as bedload. These floodplain channels are supply limited under the current hydrologic regime and identified as net erosional. On the South River floodplain in Virginia, incorporating hydrologic flowpaths as an explicit measure of river-floodplain connectivity can improve predictions of floodplain sediment deposition. Three regression models were developed incorporating flow pathways and the best model was applied to hydrodynamic model results to create a spatial map of floodplain sedimentation rate. The deposition map highlights how floodplain topography and river-floodplain connectivity affect sedimentation rates and can help inform the development of floodplain sediment budgets. Lastly, streamflow conditions were investigated in the Dan River, North Carolina as they affect juvenile freshwater mussel settling. Two uplooking velocity sensors on the river bed were deployed and hydraulic parameters were measured for a 7-mo period in May-November 2019 to estimate the juvenile mussel settling. Results show that juvenile freshwater mussels as large as 280-508 µm could always be suspended during our study period and not be able to settle onto the river bed at the location of our velocity sensors. Therefore, the flow and shear velocity during our study period was high enough to prohibit the recruitment of juvenile freshwater mussels from settling out of suspension at the sensor locations. Modest flow obstructions such as large boulders, downed trees, or large wood that create downstream wakes may be important features that provide suitable conditions for the settling of juvenile freshwater mussels onto the river bed. Furthermore, low flows have been increasing since the year 2000 which may be exacerbating the decline in freshwater mussel populations. / Doctor of Philosophy / Human civilization has developed near rivers due to the wide range of benefits provided by rivers. Rivers provide food, water, and energy to more than 2.7 billion people around the world. However, the health of the rivers is degrading rapidly to meet the increasing demand of the growing population. We studied water, sediment, and mussel transport in the three rivers in the US: East Fork White River in Indiana, South River in Virginia, and Dan River in North Carolina. These rivers play an important role in agriculture, water supply, sediment, and nutrient transport of the surrounding environment. Our research work on East Fork White River in Indiana, USA shows that the area directly adjacent to the river is eroding, which is important information for river managers and policymakers. As part of that work, we identified the potential of various sizes of sediment to move over this area at different flows and developed a method to predict the largest sediment size that could be moved in water and hopping along the ground. This method is also applicable to other areas along rivers and the coast. We estimated the sediment deposition rate, deposition volume, and prepared a spatial map of the sediment deposition pattern for the South River floodplain in Virginia. From this map, deposition hot spots could be identified. We estimated that 66% of the sediment deposited adjacent to the South River was located in 32% of the area. This information will be helpful for understanding how sediment and sediment-associated pollutants deposit around rivers. Our work on the Dan River in North Carolina was focused on freshwater mussels. Our results showed that juvenile freshwater mussels could not have settled onto the river bed at the location of our measurements. Historical data reveal that freshwater mussels are declining at an alarming rate in that river, posing a threat to the river environment. We identified that streamflow has been increasing over the last two decades, which could be a potential cause of declining freshwater mussels.

Rivers and their surrounding riparian and subsurface ecosystems, known as river corridors, are important landscape features that provide a myriad of ecological and societal benefits. While the importance of riverine flooding has been widely acknowledged and extensively studied, very little research has been conducted on the interactions between river channels and their adjacent floodplains. The importance of this hydrologic connectivity between rivers and floodplains has been emphasized in recent decades and now ecological engineering techniques such as stream restoration are often utilized to restore connectivity between streams and their riparian ecosystems. Despite its ubiquity in practice, there are still many basic components of river-floodplain connectivity that are not well understood. Furthermore, a lack of cost-effective monitoring techniques makes sustainable management of river corridors quite challenging. Thus, the overall goals of my dissertation were: 1) develop user-friendly river corridor monitoring techniques utilizing cost-effective approaches such as time-lapse digital imagery and satellite remote sensing and 2) identify the effects of anthropogenic activities on river corridor hydrologic and biogeochemical processes that occur at varying spatial and temporal scales during flood events. These goals were addressed through five independent studies that span spatiotemporal scales. The five studies utilized a combination of novel remote sensing, hydrologic/hydraulic modeling, and high frequency spatial sampling techniques to analyze river corridor dynamics. Results highlight that digital imagery and satellite remote sensing can be effective tools for monitoring river corridors in data scare regions. Additionally, impounding streams and river corridors alters floodplain connectivity and biogeochemical processing of reactive solutes such as nitrogen and phosphorus. Findings from this work highlight the important role that spatial and temporal scale plays in river corridor dynamics. Overall, this research provides new analytical techniques and findings that can be used to effectively monitor and manage river corridors. / PHD / Rivers are important landscape features that provide basic societal needs such as drinking water, water for agricultural irrigation, and hydroelectric energy. Engineers have traditionally sought to manage rivers for these purposes while also minimizing flooding. However, flooding actually provides a number of environmental benefits such as increased aquatic biodiversity and removal of excess sediment and pollutants from rivers. This notion of environmentally friendly flooding is a relatively new concept and much is still unknown about how these processes differ at varying scales. Additionally, there is currently a lack of techniques for monitoring such processes primarily due to the cost required for equipment and labor. Therefore, the goals of this dissertation were twofold: 1) develop cost-effective and user-friendly monitoring techniques that can be used to study river flooding dynamics and 2) examine the impacts of river flooding dynamics at three different spatial scales ranging from a small stream to a large watershed. This was accomplished through five separate case studies that examine rivers and watersheds of varying sizes at varying time scales. The studies utilized several emerging technologies that required a combination of field monitoring, computer simulations of flood dynamics, and satellite imagery to gain a better understanding of river flood hydrology and water quality. A key finding was the important role that scale plays in both spatial and temporal domains. Utilizing varying spatial and temporal scales allowed for identification of different processes that occur across a range of river and watershed sizes. Overall, this work can be used to better inform future river management and restoration decisions.

Understanding the factors influencing the abundance and distribution of tropical floodplain fishes is an important component of fisheries management plans to support future sustainable resource use. This thesis uses a multi-scale approach to understand the habitat factors controlling the distribution and abundance of arapaima (Arapaima spp.) in river floodplains of the lower Amazon River, near the municipality of Santarém, Para State, Brazil. In chapter 1, a study of eight environmental variables in 13 dry season floodplain lakes demonstrates that lake depth, relative depth, conductivity, and transparency were significantly related to the probability of arapaima presence at individual locations within lakes. Further, the study revealed that smaller arapaima were more likely to be found near macrophyte coverage than in open water locations. In chapter 2, a landscape scale approach was used to examine the interactions between management systems, landscape habitat coverage, and spatial arrangement on arapaima population sizes in 73 floodplain lakes. Results showed that all three influences were important in explaining variability in arapaima abundances. Management and habitat variables contributed equally in controlling arapaima abundances. Both had strong patterns of spatial arrangement and overlapped significantly, suggesting that analysis of either management systems or landscape habitats without the other would lead to overestimations of the strength of their influence. Findings from both chapters support the notion that future sustainable use of arapaima populations requires a dualistic approach combining habitat conservation with fisheries management techniques enacted at a local scale. / Master of Science / Understanding where fishes choose to live within aquatic habitats, and why they do so, is important for their long-term protection habitat destruction and overfishing. This thesis looks at fish habitats at both small and large scales to understand the variables affecting populations of the megafish arapaima (<i>Arapaima spp.</i>) in lakes of the lower Amazon River, near the municipality of Santarém, Pará State, Brazil. In chapter 1, a study of eight environmental variables in 13 lakes shows that for each lake, deeper, muddier (less clear), and more electricallyconductive waters were more likely placed to find arapaima. Further, the study revealed that young arapaima were more likely to be found near aquatic plants than in open water areas near the middle of the lake. In chapter 2, a larger-scale approach was used to examine the interactions between humans, habitats, and spatial groupings for arapaima population sizes in 73 lakes. Results showed that all three factors were important in explaining how many arapaima were found in each lake. Human and habitat variables were equally important variables affecting arapaima. Both were strongly related to spatial groupings and overlapped significantly, suggesting that analysis of either human systems or habitats without the other would lead researchers to overestimate how important they are for arapaima. Findings from both chapters support the notion that future sustainable use of arapaima populations requires an approach combining habitat conservation with fisheries management techniques enacted at a local scale.

A system of pools arises in the upper part of the Lužnice river during the spring flood. This study describes inter-annual development of phytobenthos in the floodplain system of the Lužnice River, including temporary/permanent pools during spring flood.

Amphibians are regarded as sensitive indicators of environmental change and are therefore excellent subjects for use in ecotoxicology. The Phongolo River floodplain is South Africa’s most diverse natural floodplain system and hosts more than 40 frog species. It is also a malaria endemic region and is subjected to active spraying with Dichlorodiphenyltrichloroethane (DDT) through means of indoor residual spraying over the summer months. The upper Phongolo River runs through agricultural landscape and is subjected to runoff from forest plantations, orchards and sugar cane plantations. In this study residue levels of 22 different organochlorine pesticides (OCPs) were analysed in selected amphibian species from in and around the Ndumo Nature Reserve coupled with 12 different biomarker response assays to determine environmental exposure levels and possible sublethal effects in amphibians from the lower Phongolo River floodplain. Seasonal change, direct influence of anthropogenic activity and the influence of species’ aquatic preference in habitat selection were all factors considered during this assessment. Stable Isotope analyses were performed on 11 different food web components In order to determine the food web structure pertaining to Xenopus muelleri (Müller's platanna). Samples were collected during both high and low flow seasons from inside and outside Ndumo Nature Reserve. Organochlorine pesticide bioaccumulation was analysed in whole frog samples using a GC-μECD. Results indicated significant seasonal variation in OCP levels and exposure composition. Significant differences between inside and outside sites were also noted. Dichlorodiphenyltrichloroethane in its different isomer forms and their metabolites along with the hexachlorocyclohexane (HCH) isomers was the two main contributing OCP groups detected. Total OCP levels from all sample sets ranged between 8.71 ng/g lipid and 21,399.03 ng/g lipid. An increase in OCP accumulation was observed for X. muelleri over a period of one year. Organochlorine pesticides are known to have neurotoxic effects causing imbalances in Na+, K+, and Ca+ ion exchange. Hyperactivity has been reported in Rana temporaria (European Common frog) tadpoles exposed to p,p-DDT concentrations above 110,000 ng/g lipid. Despite OCP levels measured in frogs from this study being lower than reported toxic levels, the biomarker response assays indicated definite oxidative stress responses correlating to OCP bioaccumulation, with other minor responses shown. Cellular energy allocation showed a shift in the main energy source type from proteins to lipids correlating to increased OCP bioaccumulation. A slight inhibition response was noted in the hepato-somatic index correlating to γ-HCH bioaccumulation. Stable isotope analyses indicated food web structure differences between inside and outside the reserve, with outside showing less clear distinction between trophic groups and nitrogen enrichment of primary producers. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Amphibians are regarded as sensitive indicators of environmental change and are therefore excellent subjects for use in ecotoxicology. The Phongolo River floodplain is South Africa’s most diverse natural floodplain system and hosts more than 40 frog species. It is also a malaria endemic region and is subjected to active spraying with Dichlorodiphenyltrichloroethane (DDT) through means of indoor residual spraying over the summer months. The upper Phongolo River runs through agricultural landscape and is subjected to runoff from forest plantations, orchards and sugar cane plantations. In this study residue levels of 22 different organochlorine pesticides (OCPs) were analysed in selected amphibian species from in and around the Ndumo Nature Reserve coupled with 12 different biomarker response assays to determine environmental exposure levels and possible sublethal effects in amphibians from the lower Phongolo River floodplain. Seasonal change, direct influence of anthropogenic activity and the influence of species’ aquatic preference in habitat selection were all factors considered during this assessment. Stable Isotope analyses were performed on 11 different food web components In order to determine the food web structure pertaining to Xenopus muelleri (Müller's platanna). Samples were collected during both high and low flow seasons from inside and outside Ndumo Nature Reserve. Organochlorine pesticide bioaccumulation was analysed in whole frog samples using a GC-μECD. Results indicated significant seasonal variation in OCP levels and exposure composition. Significant differences between inside and outside sites were also noted. Dichlorodiphenyltrichloroethane in its different isomer forms and their metabolites along with the hexachlorocyclohexane (HCH) isomers was the two main contributing OCP groups detected. Total OCP levels from all sample sets ranged between 8.71 ng/g lipid and 21,399.03 ng/g lipid. An increase in OCP accumulation was observed for X. muelleri over a period of one year. Organochlorine pesticides are known to have neurotoxic effects causing imbalances in Na+, K+, and Ca+ ion exchange. Hyperactivity has been reported in Rana temporaria (European Common frog) tadpoles exposed to p,p-DDT concentrations above 110,000 ng/g lipid. Despite OCP levels measured in frogs from this study being lower than reported toxic levels, the biomarker response assays indicated definite oxidative stress responses correlating to OCP bioaccumulation, with other minor responses shown. Cellular energy allocation showed a shift in the main energy source type from proteins to lipids correlating to increased OCP bioaccumulation. A slight inhibition response was noted in the hepato-somatic index correlating to γ-HCH bioaccumulation. Stable isotope analyses indicated food web structure differences between inside and outside the reserve, with outside showing less clear distinction between trophic groups and nitrogen enrichment of primary producers. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015