Floodplain lakes in the Mississippi Alluvial Valley (MAV) provide valuable freshwater resources for states in which they occur. Thirty lakes in portions of Mississippi and Arkansas were surveyed for chlorophyll-a fluorescence and turbidity using handheld meters to determine relationships between chlorophyll-a concentrations and suspended solids. High applicability of handheld meters in the MAV presents economic benefits for monitoring the numerous lakes in the region. Additionally, twelve lakes within Bear Creek watershed, Mississippi were studied to determine how hydrologic connectivity shapes fish communities. Isolated and permanently connected floodplain lakes exhibited characteristically lacustrine and rheophilic fish communities, respectively, diversifying fishery management opportunities. Lastly, spring diel temperature and oxygen dynamics, as well as juvenile fish communities, were assessed within three habitats in a floodplain lake – pelagic environment, margin and contiguous wetlands. Variability in temperature and oxygen across the three habitats promotes spring habitat heterogeneity while supporting distinct but overlapping juvenile fish assemblages.

In the United States, the floodplain maps used in the administration of the National Flood Insurance Program are created and maintained by the Federal Emergency Management Agency. Currently, a nationwide map modernization program is underway to convert the existing paper floodplain maps into a digital format, while continuing to improve the maps and expand the scope of the studies. The flood zones depicted on these maps are developed through engineering studies, using a variety of accepted methods to model and predict flood-prone areas. These methods are classified as detailed, limited detailed, or approximate, corresponding to varying levels of expense and accuracy. Current flood map revision activities across the nation typically consist of developing new hydraulic models, or reusing existing hydraulic model results in conjunction with new, more detailed LiDAR terrain models. This research develops a profile synthesis method for redelineation of approximate flood boundaries, and evaluates the method's performance and usability. The profile synthesis method is shown to perform reliably on simple floodplain geometry, recreating a water surface profile based only on its floodplain boundaries. When applied to a real-world floodplain studied in a previous flood insurance study, the profile synthesis method is shown to perform adequately, with results comparable to an approximate hydraulic model developed in HEC-RAS. Methods similar to this profile synthesis method for reuse of existing approximate zone boundaries have not been widely documented or evaluated; nevertheless, methods such as this are believed to be common in the revision of approximate zone flood boundaries. As such, this work explores concepts which will be of interest to individuals actively involved in flood map revision and modernization. / Master of Science

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.

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.

Floodplains are among the most productive and biologically diverse freshwater ecosystems on earth. The exchange of nutrients and biota that occurs within these systems during seasonal inundation is essential in maintaining floodplain and river health. Anthropogenic structures, such as weirs, channels, and dams, have altered the natural flood hydrology of floodplain systems minimizing the frequency, strength and duration of flood events. This reduction ultimately leads to the isolation of important floodplain habitat, such as off-channel lakes, from the main channel, decreasing connectivity. Although some studies have examined the productivity of off-channel floodplain lakes in relation to connectivity, most are limited to tropical or highly degraded systems. Northern floodplains are not as well understood, with most of the research limited to the spring, summer, and fall seasons, when waterbodies are free of ice. With research limited to ice free seasons, there is not a full understanding of the year-round processes that occur within these off-channel lake habitats. This knowledge is crucial as the winter season is often when conditions within these habitats are at their most extreme. Such conditions prevent many fish species from permanent settlement; however, no research has been attempted to understand fish presence within these habitats during the winter season. In tropical systems, hypoxia-tolerant species and juveniles utilize these habitats as refuge from intolerant predators, so such habitat may be used similarly in more northern systems. The purpose of this research was to understand the connectivity, limnology and suitability as fish habitat of off-channel floodplain lakes in the Saskatchewan River Delta (SRD), SK, during winter months. I determined the degree of connectivity to the main channel for 26 individual lakes within the SRD by two modern methods: remote sensing imagery, and stable isotopes (δ18O, δ2H). Both of these techniques proved effective at determining connectivity of individual lakes and showed good agreement, with lakes arranged into five connectivity categories using remote sensing imagery. Winter limnological conditions within these lakes were significantly influenced by their degree of connectivity, with lakes that were more connected having characteristics similar to that of the river, with higher levels of dissolved oxygen (DO), nitrates (NO3-NO2), pH, and lower levels of nutrients (TN,TP). Lakes that were less connected were characterized by low levels of DO and nutrients, and high levels of ammonia/ammonium (NH3-NH4), conditions that are not favourable for the survival of many fish species. Some of the more hypoxia-tolerant species found within the SRD appear, however, to use these habitats in the winter. This was supported by detection of fish presence using environmental DNA; five fish species were detected in many of the 26 lakes sampled, but only in lakes with NH3-NH4 levels below 1.77 mg/L and volumes greater than 178000 m3. Together, these analyses suggest the influence of a spring/summer flood pulse on limnology is not limited to the months following a flood event, but rather extends well into the ice-cover season. This knowledge is critical as it points to controls on key processes (e.g. nutrient cycling, provision of fish habitat) during the period when lake conditions are most severe. As a result of human induced climate change, and from increased water demands for agriculture and hydropower, the natural flood pulse is expected to further decrease in size and frequency in large river-wetlands such as the SRD. This will reduce the connection between the floodplain and the main channel, with profound impacts on the SRD ecosystem as a whole. Lakes that currently experience frequent inundation will likely have conditions characteristic of infrequently flooded lakes, with low DO and nutrients and high NH3-NH4. Lakes which currently experience infrequent inundation will likely dry up completely due to decreased water renewal.

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Growing populations and industrialized agriculture practices have eradicated much of the United States wetlands along river floodplains. One program available for the restoration of floodplains is the Conservation Reserve Program (CRP). The current research explores the effects CRP land change has on flooding zones, utilizing Flood Modeller and HEC-RAS. Modelling in both one-dimensional and two-dimensional approaches were tested and analyzed for the same river reach. Flood Modeller is proven a viable tool for flood modeling within the United States when compared to HEC-RAS. Application of the software is used in the Nodaway River system located in the western halves of Iowa and Missouri, to model the effects of introducing new forest areas within the region. Flood stage during the conversion first decreases in the early years, before rising to produce greater heights. Flow velocities where CRP land is present are reduced for long-term scopes. Velocity reduction occurs as the Manning’s roughness values increase due to tree diameter and brush density. Flood zones become more widespread with the implementation of CRP. Comparing one-dimensional and two-dimensional flood mapping zones, the two-dimensional model shows less inundation. CRP land cover effects evolve over time, with the greatest impact appearing at the end of the contract.

As conveyors of water and sediment, rivers play an instrumental role in landscape evolution (Turner et al., 2015). River systems were traditionally considered as passive pipes of terrestrial organic carbon (OC), but are now viewed as active sites of OC processing, redistribution and storage (Aufdenkampe et al., 2011). Floodplains are an important part of this system and have the capacity to act as sources or sinks of carbon (Zehetner et al., 2009), but most importantly active hotspots of organic matter (OM) transformation (Hoffmann et al., 2009; Zocatelli et al., 2013). POC eroded from highly-organic peat soils, may be interrupted in its transport through the fluvial system, by temporary storage on floodplain landforms (Evans and Warburton, 2005; Evans et al., 2006). It is important to investigate the fate of fluvial peatland POC, in order to fully close the terrestrial peatland carbon budget, to account for subsequent mineralisation and explore the processes that lead to redistribution and storage. The River Ashop in the southern Pennines, UK, drains the slopes of both Bleaklow and Kinder Scout which are upland plateaux, which support an extensive cover of blanket peat (Evans and Lindsay, 2010). These peatlands have been severely eroded and are vulnerable to future erosion as they are marginal to the climatic space suitable for growth of peat bogs in the UK (Clark et al., 2010). The wider peatland catchment features cohesive, organic-rich floodplains, which are atypical in an upland landscape, and thus suitable for investigation in their role in the fate of eroded carbon. OM quality was an important focus of this research into the redistribution of terrestrial organic carbon. As such, OM quality was conceptualised, by identifying how different research disciplines identify with the term, and ultimately providing a classification scheme to assist individuals in their exploration of OM character. A novel approach using ITRAX core scanning data was used to establish carbon stocks of floodplains in the River Ashop catchment. Sedimentological characteristics were insufficient to distinguish between allochthonous and autochthonous organic matter storage. However, dating was used as a rapid and accurate tool to assess carbon source on the 'off-site' floodplain, and could perhaps be used in the wider environment where there are large discrepancies between the ages of source materials. Investigations into the OM quality, provided suitably convincing evidence that substantial overbank deposition of eroded 'old' peat had occurred. Despite this, viewing these sites simply as areas of carbon storage is misleading. In fact, these systems have potentially been turning over substantial quantities of carbon to the atmosphere. Contextual information from modern-day fluvial POC fluxes showed that both 'off-site' and 'on-site' floodplains only play a minor role in storing carbon. Geomorphological events, particularly the substantial sediment flux generated from peatland erosion were critical in the formation of these floodplains. In these peatland systems, erosion, deposition and turnover of carbon are intimately linked at the landscape scale, and floodplains are a dynamic component of this system.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 76-85).

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