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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Lone Wolves and Copycats: Assessing Policy and Infrastructure for Flood Hazard and Floodplain Management

Hamlin, Samantha L. 04 December 2018 (has links)
To mitigate flood hazard, which affects millions of people every year, increasing numbers of communities are developing green infrastructure policies to not only mitigate the hazard, but to meet other community policy objectives, as green infrastructure is often cited for the multiple benefits it confers. To support the implementation of policies that help communities meet their policy objectives, however, it is imperative to understand how policy is innovated and adopted. To do so, I applied the internal determinants and regional diffusion models, what I refer to as the lone wolf and copycat models. In policy, a lone wolf innovates a policy to meet a specific, internal objective; this objective may include economic, environmental, or social needs. A copycat evaluates the efficacy of a policy in other municipalities before adopting it for its own use. Because infrastructure is one of the primary routes of implementing flood hazard and floodplain management policies, I developed a framework that describes the relationship between these two models. In this framework, a community may rely more heavily on either gray or green infrastructure, while also being more of a lone wolf or copycat in the ways in which it adopts policy. Based on this framework, I analyzed four Oregon communities -- Eugene, Milton-Freewater, Prineville, and Sherwood -- that exemplify these different infrastructure and policy approaches. From this case study analysis, I developed several propositions to explain why each community pursued certain policies. I then expanded this research to floodplain administrators across the state, using a key informant questionnaire to capture the managerial and demographic characteristics that correlate with the adoption of green infrastructure in over 100 Oregon communities. I found that urbanization strongly correlated with the use of green infrastructure, as did a floodplain administrator having professional experience with flooding, being knowledgeable about flood mitigation infrastructure, and talking more frequently to other floodplain administrators. Finally, I use my research framework for an in-depth case study of the internal determinants model. I focus on a community in the Portland metropolitan area, Sherwood, and a program the community developed in the early 1990s to protect extensive areas of open space, greenways, and floodplains to preserve a unique community identity. In pursuing these objectives, Sherwood spearheaded the creation of the Tualatin River National Wildlife Refuge, the first urban wildlife refuge in the country.
112

Flood risk analysis for the Iowa Statewide Floodplain Mapping Project

Reith, Benjamin Samuel 01 December 2012 (has links)
Flooding is a major hazard in the Midwest, accounting for more economic damage than any other hazard. Recent major flooding events in Iowa have created a greater need for the monitoring of floodplain areas. The objective of this paper is to evaluate flood risk through the synthesis of geospatial data with flood maps for thirteen Hydrologic Unit Codes (HUC 8s) in southwest Iowa. Using ArcGIS, exposure of ecosystem services, population, and environmental hazards can be located within the 10, 50, 100, 500 year floodplains. Additionally, the effectiveness of hydric soils as a floodplain proxy is evaluated using SSURGO soil data. An overview of FEMA HAZUS-MH 2.0 flood loss estimation software is provided and a model of the East Nishnabotna HUC 8 is evaluated. An alternative economic loss framework based on an NED land use raster and structure data is compared for the region. This study aims to provide beneficial floodplain information for development and regulation decisions.
113

The landscape-scale structure and functioning of floodplains

Sims, Neil C, n/a January 2004 (has links)
Floodplains are amongst the most productive and biodiverse ecosystems. The structure and functioning of floodplains is controlled by the interaction of intermittent inundation with the floodplain landscape. These interactions create highly complex and dynamic ecosystems that are difficult to study at large scales. Consequently, most research of floodplains has been conducted at small spatial and temporal scales. Inundation of floodplains can extend over many square kilometres, however, which unifies the floodplain landscape into an integrated ecosystem operating at the landscape scale. The lack of data and poor understanding of the landscape-scale structure and functioning of floodplains limits the possibility of managing floodplains sustainably as pressure for exploitation of their resources increases. This thesis quantifies the landscape-scale relationship between the frequency and patterns of inundation, the composition and structure of the landscape, and the functioning of the floodplain landscape in terms of the distribution and dynamics of plant growth vigour over an area of approximately 376,000 ha on the Lower Balonne Floodplain; highly biodiverse, semi-arid floodplain ecosystem that straddles the state border between New South Wales and Queensland approximately 500 km inland from the eastern coast of Australia. Mean annual rainfall at St.George, to the north of the study area, is approximately 400�450 mm per year, and median annual evaporation is approximately 2000 mm per year. Plants and animals on the floodplain are therefore heavily dependent upon flooding for survival. This project is based on the analysis of 13 Landsat Thematic Mapper satellite images captured over a 10-year period during which land and water resource development increased substantially. There is now concern that development activities have affected the functioning of the floodplain to the detriment of the natural environment and agricultural productivity. The impacts from these activities on the functioning of the floodplain are not yet known, however. Inundation of the Lower Balonne Floodplain was mapped using a two-part process involving a band ratio to identify deep clear water, and a change detection analysis to identify areas of shallower inundation. This analysis shows that, in contrast with most floodplains, the main flowpath of the Lower Balonne Floodplain runs along its central axis away from river channels, which flow along the floodplain�s outer edges. Inundation propagates from the centre of the floodplain out towards river channels as flood discharge volumes increase. Variations in the spatial pattern of inundated patches within the inundated extent create distinctive aquatic habitat and connectivity conditions at different flow levels. These can be described in terms of three connectivity phases: (I) Disconnected, in which isolated patches of inundation occur at low flows and river channels are hydrologically dislocated from the floodplain; (II) Interaction, where increased hydrological connectivity between inundated patches, and between the floodplain and the river channels at moderate flows, may enable significant exchange of materials, organisms and energy; and (III) Integration, in which almost the entire floodplain landscape is connected by open water during large magnitude floods. There is an abrupt transition in inundation patterns as flows increase between 60,000 ML day-1 and 65,000 ML day-1 (ARI 2 to 2.3 years) in which inundation patterns transform from being relatively disconnected into a highly integrated network of patches. These patterns may have significant consequences for the structure and functioning of the floodplain. Increases in flows across this small range may therefore mark an important ecological flow threshold on this system. Water resource development impacts have changed the relative frequency of flows on the Lower Balonne Floodplain, which will probably affect the sequence of connectivity phases over time. The most likely impact of these changes will be to create a floodplain that is drier overall than under natural flow conditions, and that has a smaller and wetter area of high inundation frequency. The relationship between inundation and the structure of the floodplain landscape was examined by comparing a landcover map showing the distribution and character of 10 landcover types to the inundation frequency maps. Landcover types were mapped from a multi-date Reference Image composite of seven images captured over a period of 10 years. The Reference Image improves landcover discrimination by at least 14% over classification of a single-date image, and has an overall accuracy between 82.5% and 85% at the landscape-scale. The Reference Image shows that the landscape of the Lower Balonne Floodplain is a highly fragmented mosaic of diverse landcover types distributed in association with inundation frequency. Stratifying the floodplain into zones of frequent and rare inundation shows that frequently inundated areas have a less fragmented but less diverse landscape structure than rarely inundated areas. Assessment of the functioning of each landcover types within the floodplain ecosystem, based on landscape pattern metric analysis, indicates that the function of landcover types also changes between inundation frequency zones. Most importantly, these changes include a transformation of the matrix landcover type, which controls the character and dynamics of the ecosystem overall, from Open Grassland to Coolibah Open Woodland in the frequently inundated zone. The landscape structure of the Lower Balonne Floodplain has been affected by development impacts, which include clearing of native vegetation, isolation of parts of the floodplain from natural inundation events by the construction of levee banks and drainage channels, and grazing impacts. Changes to the inundation regime may also affect the structure of the floodplain landscape. Over the long term, these changes are likely to create a larger area of Open Grassland and a smaller area of Coolibah Open Woodland as the zone of frequent inundation becomes smaller and wetter. To examine the functioning of the floodplain ecosystem, the inundation maps were compared to remotely sensed indexes of plant growth vigour at the landscape and landcover-type scales. The dynamics of plant growth vigour over time are influenced by factors operating at the regional, landscape and patch scales. Evaporation is the major control of growth vigour levels at the landscape scale, but each landcover type has a distinctive pattern of growth vigour dynamics that is related to its composition and location, and possibly its landscape structure. The association between the spatial distribution of plant growth vigour and inundation frequency is non-linear, with the highest growth vigour occurring where inundation occurs approximately once per year. This indicates a subsidy-stress interaction with water in which plant growth vigour is limited by soil anoxia in areas of frequent or long term inundation, and by drought stress in rarely inundated areas. A landscape-scale model of growth vigour dynamics, founded on the principles of Hierarchical Patch Dynamics and Landscape Ecology, was created from growth vigour measurements of each landcover type over time. This model was used to examine possible impacts of development activities on the functioning of the floodplain ecosystem. This model shows that the response of plant growth vigour development activities can be complex and subtle, and include a change in mean long-term growth vigour and an increased susceptibility to drought. The model also indicates that periods of high growth vigour can occur in substantially altered floodplain ecosystems. The model was also used to explore the levels of landcover change that might cause a threshold change in the functioning of the ecosystem, which may substantially alter the disturbance-response characteristics of the floodplain ecosystem. The model indicates a threshold change when the extent of Open Grassland is reduced by 30% of its extent in 1993, in which plant growth vigour response to disturbance is virtually inverted from that observed in the images. The temporal variability of plant growth vigour levels increases as the extent of Open Grassland is further reduced. This thesis makes a number of important contributions to our understanding of floodplain structure and functioning. It includes the development of new techniques suited to studying large diverse and complex landscapes at the landscape scale from satellite images, and provides quantitative data describing the links between the structure of floodplain landscapes and their functioning at the landscape scale. This work improves the understanding of floodplain ecosystems by integrating models of floodplain structure and functioning, which have been developed largely from smaller-scale studies of temperate and tropical floodplains, with landscape-scale measurements of this semi-arid system. This thesis also has implications for the Lower Balonne Floodplain by improving the level of information about this important ecosystem and providing baseline data against which the condition of the floodplain can be assessed in future.
114

Eucalypt regeneration on the Lower Murray floodplain, South Australia.

George, Amy Kathryn January 2004 (has links)
Vegetation along the River Murray floodplains has been shown to be in a severe state of decline. This decline is amplified by the impositions of river regulation. In South Australia, where vegetation losses have been great, regeneration is limited and may result in not only individual tree losses but also widespread population decline. This study aimed to examine the relationship between river flows and the regeneration process in populations of Eucalyptus camaldulensis and Eucalyptus largiflorens. The current structure of the populations was examined to determine if a viable number of varying age-classed trees were present. Tree surveys conducted at Banrock Station determined that while densities were low for both species, E. camaldulensis had a more sustainable population structure than E. largiflorens. Growth stages for both species illustrated highly clumped distribution, which is believed to correspond with river flooding magnitudes and frequencies. To address the potential link between tree distribution and flooding within the River Murray, a hydrological analysis was conducted for Banrock Station using river flows at the South Australian border from 1900 to 2003. The amount of time growth stages for each species were inundated was found to be greatly reduced under regulated flows compared to natural flows. This has resulted in shifted localized regeneration patterns corresponding with E. camaldulensis' greater demand for inundation than E. largiflorens. Moderate magnitude flows have been most impacted by regulation, and consequently these are the very flows needed for floodplain tree population maintenance. Flowering and seed fall for E. camaldulensis and E. largiflorens were monitored at Banrock Station for 22 months to identify losses in reproductive potential resulting from tree decline. While seed viability was not affected by vigour, trees with visually reduced vigour were found to produce less fruit and had reduced seed fall, as well as a reduced rate of fruit development. Dendrochronological techniques were applied to floodplain trees. Age and size relationships could be established, implying that such techniques can be applied in South Australia to high quality sites. Growth responses within cohorts were similar and easily matched between individuals illustrating cyclic, but not necessarily seasonal correlations. This work verified the preferential selection of younger trees for dendroecological studies, and identified a relationship between on moderate flows and measurable girth expansion in both floodplain tree species. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.
115

Connectivity Drives Function: Carbon and Nitrogen Dynamics in a Floodplain-Aquifer Ecosystem

Appling, Alison Paige January 2012 (has links)
<p>Rivers interact with their valleys from headwaters to mouth, but nowhere as dynamically as in their floodplains. Rivers deliver water, sediments, and solutes onto the floodplain land surface, and the land in turn supplies solutes, leaves, and woody debris to the channel. These reciprocal exchanges maintain both aquatic and terrestrial biodiversity and productivity. In this dissertation I examine river-floodplain exchanges on the well-studied Nyack Floodplain, a dynamic, gravel-bedded floodplain along the Middle Fork Flathead River in the mountains of northwest Montana. I quantify exchanges at multiple timescales, from moments to centuries, to better understand how connectivity between aquatic and terrestrial habitats shapes their ecology.</p><p>I first address connectivity in the context of a long-standing question in ecosystem ecology: What determines the rate of ecosystem development during primary succession? Rivers have an immediate effect on floodplains when scouring floods remove vegetation and nutrients such as nitrogen (N) and leave only barren soils, but they might also affect the ensuing primary succession through the gradual delivery of N and other materials to floodplain soils. I quantify N inputs to successional floodplain forest soils of the Nyack Floodplain and find that sediment deposition by river flood water is the dominant source of N to soils, with lesser contributions from dissolved N in the river, biological N fixation, and atmospheric deposition. I also synthesize published rates of soil N accumulation in floodplain and non-floodplain primary-successional systems around the world, and I find that western floodplains often accumulate soil N faster than non-floodplain primary successional systems. My results collectively point to the importance of riverine N inputs in accelerating ecosystem development during floodplain primary succession.</p><p>I next investigate the role of river-floodplain exchanges in shaping the spatial distribution of a suite of soil properties. Even after flood waters have receded, dissolved N, carbon (C), and moisture could be delivered from the river to floodplain soils via belowground water flow. Alternatively, C inputs and N withdrawals by floodplain vegetation might be a dominant influence on soil properties. To test these hypotheses, I excavated and sampled soil pits from the soil surface to the water table (50-270 cm) under forests, meadows, and gravel bars of the Nyack Floodplain. Near-surface soils had C and N pools and N flux rates that varied predictably with vegetation cover, but soil properties below ~50 cm reflected influence by neither vegetation cover nor aquifer delivery. Instead, soil properties at these depths appear to relate to soil texture, which in turn is structured by the river's erosional and depositional activities. This finding suggests the revised hypothesis that soil properties in gravel-bedded alluvial floodplains may depend more on the decadal-scale geomorphic influences of floods than on short-term vertical interactions with floodplain vegetation or aquifer water. </p><p>Lastly, I explore the potential sources of organic C to the diverse and active community of aquatic organisms in the floodplain aquifer, where the lack of light prohibits in-situ organic C production by photosynthesis. I quantify floodplain carbon pools and the fluxes of organic carbon connecting the aquifer, river, and overlying forest. Spring flood waters infiltrating the soil are responsible for the largest dissolved carbon flux into the aquifer, while very large floods are essential for the other major C input, the burial of woody carbon in the aquifer. These findings emphasize the importance of a dynamic river hydrograph - in particular, annual floods and extreme annual floods - in delivering organic C to the aquifer community. </p><p>Overall, this dissertation draws our attention not just to the current exchanges of C, N, water, and sediment but to the episodic nature of those exchanges. To fully understand floodplain ecosystems, we have to consider not just present-day interactions but also the legacies of past floods and their roles in delivering solutes, eroding forests, depositing sediments, and physically shaping the floodplain environment.</p> / Dissertation
116

Floodplain risk analysis using flood probability and annual exceedance probability maps /

Smemoe, Christopher M., January 2004 (has links) (PDF)
Thesis (Ph. D.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2004. / Includes bibliographical references (p. 223-229).
117

A watershed approach to decrease flooding of Pipe creek in Alexandria, Indiana

Zapf, Jeff January 1996 (has links)
This project explores one method of controlling flooding of Pipe Creek in Alexandria, Indiana. The method used is one of placing wetlands and grass filters within one subwatershed of Pipe Creek to reduce peak discharge and the time to peak discharge. A computer program called Sedimot II was used to determine the peak discharge for the Thurston Ditch subwatershed of Pipe Creek. Both 10 and 50 year 24 hour storms were studied. Following the construction of base line hydrographs for both storm events, four examples of wetland and grass filter placement were shown for the watershed. Hydrographs were then produced for all four alternatives for both 10 and 50 year storms. Recommendations were then made on how these examples could be used in the rest of the Pipe Creek watershed to further reduce the potential for flooding in Alexandria. / Department of Landscape Architecture
118

Fish Assemblage and Food Web Structure in Whedos (Shallow Floodplain Habitats) of the Oueme River, West Africa

Jackson, Andrew 2012 August 1900 (has links)
In the Oueme River, a lowland river in Benin, Africa, artificial ponds constructed in the floodplain (whedos) are colonized during the high-water period by a presumably random sample of fishes from the river channel. As water slowly recedes from the floodplain, fishes are isolated in whedos until they are harvested near the end of the dry season. I surveyed fishes in whedos and adjacent main-channel and floodplain habitats during two low-water (2008 and 2009) and one falling-water (2010-2011) periods, and measured a suite of physicochemical variables including dissolved oxygen, temperature, specific conductivity, and percent cover of aquatic vegetation in the falling-water period to investigate if fish assemblage structure of whedos resulted from stochastic or deterministic processes. I also investigated food web structure of whedos by analyzing carbon (delta13C) and nitrogen (delta15N) stable isotope ratios of fish and primary producer tissue samples, and samples of net primary production, soluble reactive phosphorus (SRP), NH4+, NO2-, and NO3- collected during the falling-water period. Whedos were covered with dense growth of aquatic vegetation, and dissolved oxygen concentrations were lower in whedos compared to a natural floodplain depression and the main channel. Multivariate analyses revealed that habitat types were distinct with regard to fish assemblage structure and abiotic conditions. Assemblages in whedos and natural floodplain depressions were differentiated from those of the river channel, with the floodplain habitats being dominated by piscivorous fishes that tolerate aquatic hypoxia. These results indicate that fish assemblage structure of whedos was influenced by deterministic processes during the falling- and low-water periods when these water bodies were isolated. Floodplain habitats were more nutrient-rich than the river channel, and whedos were net heterotrophic. Microphytobenthos and C3 macrophytes accounted for a large fraction of fish biomass in whedos, compared with the river channel, which was mainly supported by seston. Whedo food webs had fewer trophic transfers compared to the food web of the river channel.
119

Regional and Local-Scale Population Genetic Structure of a Primitive Teleost, the African Bonytongue (Heterotis niloticus), in Rivers of West Africa

Carrera, Elizabeth 2012 August 1900 (has links)
The African bonytongue (Heterotis niloticus), one of two living species of the primitive teleost family Arapaimidae, constitutes an important artisanal and commercial fishery in West Africa. This species has also been proposed for wide aquaculture use in Africa. Despite its importance, information on the levels of genetic differentiation for this fish in Benin is lacking, which can contribute to its conservation and management. In this study, regional and local scale genetic differentiation of the African bonytongue in Benin, West Africa, was examined using six microsatellite markers. In total, 221 H. niloticus individuals were sampled from 12 localities in Benin that include three river basins: Oueme-So (ten localities sampled); Mono (one locality); and Niger (one locality). The results showed a high degree of genetic differentiation between African bonytongue samples from the three river basins, which was expected given the barriers for dispersal for aquatic organisms. For the Oueme-So floodplain, they indicate high and homogeneous gene flow, suggesting that seasonal flooding facilitates gene flow across this region. The information obtained from this study will be useful for defining management units for H. niloticus in Benin, and caution against the translocation of individuals from different basins.
120

Channel morphology and restoration of Sitka spruce (Picea stichensis) tidal forested wetlands, Columbia River, U.S.A. /

Diefenderfer, Heida Lin, January 2007 (has links)
Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 88-102).

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