Extreme flooding and excess nutrient pollution have been detrimental to river health under increased environmental stress from human activities (e.g., agriculture, urbanization). Riverine flooding can be detrimental to human life and infrastructure yet provides important habitat and ecosystem services. Traditional flood control approaches (e.g., levees, dams) negatively impact habitat and ecosystem services, and cause flooding elsewhere along the river. Prior studies have shown that stream restoration can enhance flood attenuation, and increased exchange of water between the channel and floodplain can improve water quality. However, the effects of floodplain restoration during small and sub annual recurrence interval storms have not been thoroughly studied, nor have cumulative impacts of floodplain restoration on water quality at watershed scales. We used HEC-RAS to perform 1D unsteady simulations on a 2nd-order generic stream from the Chesapeake Bay Watershed to study flood attenuation under small and sub-annual recurrence interval storms (i.e., 2-year, 1-year, 0.5-year, and monthly). In HEC-RAS we varied percent of channel restored, location of restoration, bank height of restoration, floodplain width, and floodplain Manning's n. Overall, stream restoration reduced peak flow (up to 37%) and decreased time to peak (up to 93%). We found the timing of tributary inflows could obscure the attenuation achieved, and even reverse the trends with certain parameters in the sensitivity analysis. The greatest exchange with the floodplains (greater volume and exchange under more recurrence interval storms) was observed from Stage 0 restoration, which reduces bank height more than other approaches. We also conducted a quantitative literature synthesis of nitrate removal rates from stream restoration projects. We focused on how removal rates varied with properties relevant at watershed scales, such as effects of stream order. The resulting database will aid in determining which stream restoration parameters better reduce nutrient loads and in simulating the effects of stream restoration on water quality at watershed scales. Floodplain restoration practices, and particularly Stage 0 approaches, enhance flood attenuation which can help to counteract urban hydrologic effects. / Master of Science / Extreme flooding and excess nutrient pollution have been detrimental to river health under increased environmental stress from human activities (e.g., agriculture, urbanization). Riverine flooding can be detrimental to human life and infrastructure yet provides important habitat and ecosystem services. Traditional flood control approaches (e.g., levees, dams) negatively impact habitat and ecosystem services, and cause flooding elsewhere along the river. Prior studies have shown that stream restoration can enhance flood attenuation and aid in removal of excess nutrients. Previous studies have shown that stream restoration helps to transport nutrients to highly reactive soils and increases time for reactions. However, the effects of floodplain restoration during small and sub annual recurrence interval storms have not been thoroughly studied, nor have cumulative impacts of floodplain restoration on water quality at watershed scales. To fill these knowledge gaps, increased understanding of stream restoration design parameters and watershed level characteristics (e.g., tributary inflows, nutrient loads, etc.) is necessary. We used HEC-RAS to study flood attenuation via stream restoration under small and sub-annual recurrence interval storms on a generic stream from the Chesapeake Bay Watershed. In HEC-RAS we varied percent of channel restored, location of restoration, bank height of restoration, floodplain width, and floodplain Manning's n (surface roughness). Overall, stream restoration did reduce peak flow and decrease time to peak, which means that restoration can diminish negative flooding effects. The greatest exchange with the floodplains was observed under Stage 0 restoration, which reduces bank height more than other approaches. We also conducted a quantitative literature synthesis to collect nitrate removal rates from stream restoration projects. We focused on how removal rates varied with properties relevant at watershed scales, such as effects of stream order. The resulting database will aid in determining which stream restoration parameters better reduce nutrient loads and in simulating the effects of stream restoration on water quality at watershed scales. These efforts will help to inform practitioners how to construct stream restoration projects that are more efficient for flood control and nutrient reduction. Floodplain restoration practices, particularly Stage 0 approaches, enhance flood attenuation and exchange which can help to counteract urban hydrologic effects.

Human land use practices such as urbanization and agriculture contribute excess nutrients (nitrogen and phosphorus) and runoff volumes to rivers that degrade aquatic ecosystems and cause a loss of river functions such as nutrient processing and flood attenuation. Floodplain restoration increases floodplain exchange and is commonly implemented to improve water quality and reduce flood impacts at watershed scales. However, the effect of multiple restoration projects at the watershed scale is not well studied. We addressed this knowledge gap by two studies. The first study evaluated the impact of cumulative and spatially varying Stage-0 and bankfull floodplain restoration on nitrate removal in a generic 4th-order Virginia Piedmont watershed for small and sub-annual storm sizes (i.e. 2-year, 1-year, half-year, and monthly recurrence intervals). We used HEC-RAS hydraulics results from a prior study together with a nitrate removal model coded in R. Results indicated that watershed nitrate removal varied depending on the location of restoration in the watershed and where removal was evaluated. The greatest reductions in nitrate loads were observed in the same part of the river network where restoration occurred, with diminished impacts downstream. Removal also increased with increasing stream order/river size. However, removal was generally of small magnitude, with up to 1% or 19% of the watershed load removed for median or 90th-percentile removal rates, respectively. We estimated removal for our restoration scenarios under the Chesapeake Bay Program Protocols and found the removal rate to also be a critical factor in determining the efficiency of restoration project. Other controlling factors for nitrate removal were the amount of restoration and storm size. The second study entailed modeling cumulative restoration in a case study watershed to assess the impacts on nutrient removal and flood attenuation. We built a 1D HEC-RAS model of the 4th-order Gwynns Falls watershed near Baltimore MD using georeferenced HEC-RAS model geometries from the Maryland Department of the Environment and simulated unsteady stormflow hydraulics due to cumulative Stage-0 floodplain restoration for small and sub-annual storms. Restoration actually increased peak flow on the main channel (up to 0.9%) due to slowing of the flood wave on the main channel which was then better synchronized with tributary inflows. Restoration increased nitrate removal but at low levels (up to 0.12% or 2.6% removal for a median and 90th-percentile removal rate respectively) due to the small footprint of restoration in the watershed (up to 21.4% of the main channel was restored). These small and sometimes adverse outcomes occurred in response to what would be expensive restoration. Therefore, we argue for large-scale solutions to address watershed-scale water quality and flooding issues yet acknowledge re-evaluation of restoration goals against other societal priorities may be necessary. Overall, our results highlight the potential value and limitations of floodplain restoration in reducing flooding and nitrate exports at the channel network scale and provide practical insight for application of floodplain modeling at the watershed scale. / Master of Science / Human land use practices such as building cities and farms adds nutrients (nitrogen and phosphorus) and increase storm flows in rivers downstream. While nutrients and flows are needed for humans and wildlife, too much of either can harm aquatic organisms and endanger people and property. Floodplain restoration is a common river engineering technique that increases exchange between the river channel and low-lying areas next to rivers known as floodplains. Floodplains are natural features, but people have reduced river flows between channels and floodplains in many ways. For example, by allowing sediments to build up in floodplains or building levees that separate channels from adjacent floodplains. Increasing floodplain exchange by floodplain restoration is commonly implemented to improve water quality and reduce the impact of flooding in watersheds, which are large areas that drain to a single river. However, while the goals of restoration are often at watershed scales, the effect of multiple restoration projects at that watershed scale is not well studied. We addressed this knowledge gap by two studies. The first study evaluated the impact of multiple restoration projects and project locations in a generic (average/typical) watershed on nitrate removal. We used a nitrate removal model and the results from a prior study that modeled the stormflow behavior resulting from floodplain restoration. Results indicated that watershed nitrate removal varied depended on the location of restoration in the watershed and where removal was evaluated. The most nitrate was removed where restoration occurred, with less removal downstream in the watershed. Removal also increased with increasing river size. However, removal was generally small with up to 1% or 19% of the watershed load removed for a smaller and larger nitrate removal rate, respectively. Other factors that changed the amount of nitrate removed were the amount of restoration, nitrate removal rate in the floodplains, and storm size. The second study entailed modeling cumulative restoration in a case study watershed to assess the impacts on nitrate removal and reducing flooding. We modeled stormflow for multiple hypothetical restoration projects in the Gwynns Falls watershed and found that restoration can actually increase peak flow when placed in certain locations. Restoration increased removal but at low levels (up to 0.12% or 2.6% for a smaller and larger removal rate) due to the small amount of restoration simulated. These small and sometimes adverse outcomes occurred in response to what would be expensive restoration projects to construct. Therefore, we argue for large-scale solutions to address watershed-scale water quality and flooding issues yet acknowledge that re-evaluation of restoration goals against other societal priorities may be necessary. Overall, our results highlight the potential value and limitations of using floodplain restoration to reduce flooding and nutrient exports and provide practical insight for using our modeling techniques in managing watershed flows and pollution.

Severe flooding and excess nutrient pollution, exacerbated by heightened anthropogenic pressures (e.g., climate change, urbanization, land use change, unsustainable agricultural practices), have been detrimental to riverine systems and their estuaries. The degradation of riverine systems can negatively impact human and environmental health, as well as local, regional, and even global economies. Floods provide beneficial ecosystem services (e.g., processing pollutants, transferring nutrients and sediment, supporting biodiversity), but they can also damage infrastructure and result in the loss of human life. Meanwhile, eutrophication can cause anoxic dead zones, harming aquatic ecosystems and public health. To address the issues facing riverine systems, focus has shifted to watershed-scale management plans. However, it can prove challenging to quantify the cumulative impacts of multiple stream restoration projects within a single watershed on flooding and nutrient removal. Previous studies have quantified the effects of stream restoration on flood attenuation. However, our first study fills a substantial knowledge gap by evaluating the impacts of different floodplain restoration practices, varied by location and length, on flood attenuation and floodplain inundation dynamics at the watershed scale during more frequent storm recurrence intervals (i.e., 2-year, 1-year, 0.5-year, and monthly). We created a 1D HEC-RAS model to simulate the effects of Stage 0 restoration within a 4th-order generic watershed based on the Chesapeake Bay watershed. By varying the percent river length restored and location, we found that Stage 0 restoration, especially in 2nd-order rivers, can be particularly effective at enhancing flood attenuation and floodplain inundation locally and farther downstream. We addressed the water quality component by using a random forest machine learning approach coupled with artificial neural networks to find trends and predict nitrate removal rates associated with spatial, temporal, hydrologic, and restoration features. Our results showed that hydrologic conditions were the most important variable for predicting actual nitrate removal rates. Overall, both studies demonstrate the importance of hydrologic connectivity for flood attenuation, channel-floodplain exchange, and nutrient processing. / Maryland Department of Natural Resources; National Fish and Wildlife Foundation through the U.S. Environmental Protection Agency’s Chesapeake Bay Program Office; Chesapeake Bay Trust / Master of Science / Severe flooding and nutrient pollution from sources such as urban and agricultural runoff have been detrimental to the health of rivers. The degradation of rivers can negatively impact human and environmental health, as well as local, regional, and even global economies. Floods can be both helpful, by providing water quality benefits and supporting wildlife, and harmful, causing damage and even loss of life. Excess nutrients, such as nitrogen, can create underwater zones void of life, with serious consequences for aquatic life and public health. To address the flooding and water quality issues facing rivers, focus has shifted to landscapelevel river network management plans. However, it can prove challenging to understand the impacts of multiple stream restoration projects within a larger river network on flooding and nutrient removal. We address the flooding component by using a model to simulate the effects of different floodplain restoration techniques on a medium-sized watershed that is generally based on streams that flow into the Chesapeake Bay. Our model simulated small, relatively frequent storm events that, on average, occur every two years to once a month. By varying restoration length and location, we found that restoration practices with lower streambanks can be particularly effective at slowing down floods, reducing their overall severity by allowing more water to access the floodplains. This was especially true when restoration occurred in smaller streams, and the effects were seen both locally and farther downstream. We address the water quality component by using a different model to find patterns and predict nutrient removal rates associated with different landscape, seasonal, storm event, and restoration features. Our results showed that the most important variable for predicting nutrient removal rates was whether a stream was experiencing normal flow or stormflow conditions. Overall, both studies demonstrate the importance of restoring rivers in a manner that encourages water to flow from the channel into the floodplains during smaller storm events, because this will reduce the severity of downstream flooding while simultaneously improving water quality.

The molluscs are very suitable model of invertebrate group for ecological and palaeoecological studies for their specific traits. In the first part of the thesis, we showed based on available fossil mollusc successions that development of the floodplain mollusc fauna took place quite different way in various river floodplains, depending on their specifics and geographical location, because especially the ones situated in the chernozem area of the Czech Republic had very different history. Detailed processing of five fossil mollusc successions in the lower Ohře River floodplain confirmed the impoverishment of recent forest malacofauna does not relate to natural processes only (chapters 3 and 10), but it arises from historical development of this area which was under permanent stress of the human settlement and agricultural utilization (chapter 1) since the coming of the Neolithic people. We made similar conclusions in case of another 11 fossil mollusc successions in the neighbouring České Středohoří Mts. (chapter 2). In the second part of the thesis (chapter 3), we investigated the ecological patterns responsible for species richness and composition of the floodplain mollusc fauna are especially the elevation and humidity gradient, and then vegetation type and its biomass, light conditions of the...

Estudos biogeomorfológicos integrando a geomorfologia fluvial, neotectônica e a vegetação foram aplicados na ilha da Marchantaria, com a finalidade de analisar a distribuição da vegetação de várzea nas feições geomorfológicas. A planície do rio Amazonas é um mosaico de feições morfológicas de dimensões espaciais ora menores, ora maiores tais como ilhas, bancos arenosos, furos, paranás e lagos, que pela dinâmica fluvial estão continuamente se modificando. No canal do rio Amazonas, a ilha da Marchantaria, situada no baixo curso do rio Solimões motiva relevante interesse, tendo em vista a sua evolução areal nos últimos quarenta anos, bem como, a sua proximidade ao Encontro das Águas de Manaus EAM. A partir do arranjo dos elementos neotectônicos que condicionam as formas quaternárias atuais da ilha foram identificadas duas unidades estruturais distintas: Depósito Aluvial Subrecente (DASr) e Depósito Aluvial Recente (DAR). Também, foram definidas as unidades morfossedimentares holocênicas: feições espiras de meandro e barras de soldamento. A distribuição espacial da vegetação sobre as diferentes elevações do terreno foram agrupadas em duas unidades: vegetação lenhosa e vegetação herbácea. Os resultados mostram que: a) a vegetação distribui-se espacialmente nos diferentes níveis tectono-topográficos; b) a erosão fluvial, à montante da ilha, remove gradativamente a vegetação árborea, no entanto, à jusante, está ocorrendo sedimentação, propiciando a colonização de espécies herbáceas; c) a vegetação da ilha apresenta-se alterada devido à ação antrópica. / Biogeomorphologics studies, integrating fluvial geomorphology, neotectonic and vegetation, were applied on the island of Marchantaria, in order to analyze the distribution of vegetation in the floodplain geomorphological features. The Amazon River floodplain is a mosaic of morphological features from sometimes smaller spatial dimensions, sometimes larger such as islands, sandbars, furos, multichannels and lakes, the river dynamics that are continually changing. In the channel of the Amazon River, the island of Marchantaria, located on the lower course of the river Solimões, motivates relevant interest given its areal developments in the last forty years, as well as its proximity to the Encontro das Águas de Manaus - EAM. From the arrangement of neotectonic elements that condition the current quaternary forms of the island, two distinct structural units were identified: Sub-recent Alluvial Deposit (SrAD) and Recent Alluvial Deposit (RAD). The Holocene morpho-sedimentary units were also defined: features of scroll bars and annexation bars. The spatial distribution of vegetation on different ground elevations were grouped into two units: woody vegetation and herbaceous vegetation. The results show that: a) vegetation is distributed spatially in different tectono-topographic levels; b) fluvial erosion, the upstream of the island, gradually removes the arboreal vegetation, however, the downstream sedimentation is occurring, leading to colonization of herbaceous species; c) the island\'s vegetation is altered due to human action.

This research examined the influence of hydrochory (seed dispersal via water), anemochory (seed dispersal via wind), and zoochory (seed dispersal by animals) on the re-establishment of the important floodplain vegetation communities of the Kissimmee River floodplain. Fifty-eight seed species were identified from 19,849 and 43, 894 seeds trapped in hydrochory traps in sites north and south of Oak Creek, respectively. Seeds trapped by anemochory were measurable but were found to be far less important than hydrochory, while results showed no evidence of zoochory .... A number of interafting factors, e.g. hydrology, lack of remnants, seed phenology, etc. are limiting the dispersal of broadleaf marsh species north of Oak Creek, delaying range, expansion, and further community restoration. / by Garren Mezza. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Estudos biogeomorfológicos integrando a geomorfologia fluvial, neotectônica e a vegetação foram aplicados na ilha da Marchantaria, com a finalidade de analisar a distribuição da vegetação de várzea nas feições geomorfológicas. A planície do rio Amazonas é um mosaico de feições morfológicas de dimensões espaciais ora menores, ora maiores tais como ilhas, bancos arenosos, furos, paranás e lagos, que pela dinâmica fluvial estão continuamente se modificando. No canal do rio Amazonas, a ilha da Marchantaria, situada no baixo curso do rio Solimões motiva relevante interesse, tendo em vista a sua evolução areal nos últimos quarenta anos, bem como, a sua proximidade ao Encontro das Águas de Manaus EAM. A partir do arranjo dos elementos neotectônicos que condicionam as formas quaternárias atuais da ilha foram identificadas duas unidades estruturais distintas: Depósito Aluvial Subrecente (DASr) e Depósito Aluvial Recente (DAR). Também, foram definidas as unidades morfossedimentares holocênicas: feições espiras de meandro e barras de soldamento. A distribuição espacial da vegetação sobre as diferentes elevações do terreno foram agrupadas em duas unidades: vegetação lenhosa e vegetação herbácea. Os resultados mostram que: a) a vegetação distribui-se espacialmente nos diferentes níveis tectono-topográficos; b) a erosão fluvial, à montante da ilha, remove gradativamente a vegetação árborea, no entanto, à jusante, está ocorrendo sedimentação, propiciando a colonização de espécies herbáceas; c) a vegetação da ilha apresenta-se alterada devido à ação antrópica. / Biogeomorphologics studies, integrating fluvial geomorphology, neotectonic and vegetation, were applied on the island of Marchantaria, in order to analyze the distribution of vegetation in the floodplain geomorphological features. The Amazon River floodplain is a mosaic of morphological features from sometimes smaller spatial dimensions, sometimes larger such as islands, sandbars, furos, multichannels and lakes, the river dynamics that are continually changing. In the channel of the Amazon River, the island of Marchantaria, located on the lower course of the river Solimões, motivates relevant interest given its areal developments in the last forty years, as well as its proximity to the Encontro das Águas de Manaus - EAM. From the arrangement of neotectonic elements that condition the current quaternary forms of the island, two distinct structural units were identified: Sub-recent Alluvial Deposit (SrAD) and Recent Alluvial Deposit (RAD). The Holocene morpho-sedimentary units were also defined: features of scroll bars and annexation bars. The spatial distribution of vegetation on different ground elevations were grouped into two units: woody vegetation and herbaceous vegetation. The results show that: a) vegetation is distributed spatially in different tectono-topographic levels; b) fluvial erosion, the upstream of the island, gradually removes the arboreal vegetation, however, the downstream sedimentation is occurring, leading to colonization of herbaceous species; c) the island\'s vegetation is altered due to human action.

Laboratory experiments concerning stage-discharge, flow resistance, bedforms, sediment transport and flow structures have been carried out in a meandering channel with simulated non-vegetated and vegetated floodplains for overbank flow. The effect of placing solid blocks in different arrangements as a model of rigid, unsubmerged floodplain vegetation on a floodplain adjacent to a meandering channel is considered. The aim was to investigate how density and arrangements of floodplain vegetation influence stage-discharge, flow resistance, sediment transport and flow behaviours. Stage-discharge curves, Manning's n and drag force FD are determined over 165 test runs. The results from the laboratory model tests show that the placing of solid blocks along some part of the bend sections has a significant effect on stage-discharge characteristics. The change in stage-discharge by the blocks is compared using different arrangements, including the non-vegetated floodplains case. The experimental results show that the presence of energy losses due to momentum exchange between the main channel and the floodplain as well as the different densities of the blocks on a floodplain induce additional flow resistance to the main channel flow, particularly for shallow overbank flows. In general, the results show that the density and arrangement of blocks on the floodplains are very important for stage-discharge determination and, in some cases, for sediment transport rates, especially for a mobile main channel. Also, the correction parameter, a is introduced in order to understand the effects of blocks and bedforms on the force balance equation. By applied the correction factor c; a stagedischarge rating curve can be estimated when the avalue is calibrated well. Telemac 2D and 3D were applied to predict mean velocity, secondary flow and turbulent kinetic energy. Telemac computations for non-vegetated and vegetated floodplain cases in a meandering channel generally give reasonably good predictions when compared with the measured data for both velocity and boundary shear stress in the main channel. Detailed analyses of the. predicted flow variables were therefore carried out in order to understand mean flow mechanisms and secondary flow structures in compound meandering channels. The non-vegetated and two different cases of vegetated floodplain for different relative depths were considered. For the arrangement on a non-vegetated floodplain shows how the shearing of the main channel flow as the floodplain flow plunges into and over the main channel influences the mean and turbulent flow structures, particularly in the cross-over region. While applying vegetated floodplain along a cross-over section confirmed that the minimum/reduction shearing of the main channel flow by the floodplain flow plunging into and over the main channel is observed from the cross-sectional distributions of the streamwise velocity (U), lateral velocity (V), and secondary flow vectors. In addition to that, the vegetated floödplain along the apex bend region shows a small velocity gradient within the bend apex region. However, strong secondary flow in the cross-over section suggested that the flow interaction was quite similar to the non vegetation case in the cross-over section region.

No description available.

The Tonle Sap is the largest and most important natural wetland in Southeast Asia. It covers an area of more than 15,000 km2 with a unique mosaic of natural and agricultural floodplain habitats that coexist with the largest fishery in the Mekong Basin. Accelerating hydropower development and climate change, however, are altering the Mekong’s hydrology, which could negatively affect downstream ecosystems. The Tonle Sap is facing a two-fold problem. First, the link between its hydrology and ecosystem properties is not well understood. Second, potential ecological changes caused by future hydrological disruptions related to hydropower and climate change are unknown. Thus, the main objective of this thesis was to quantify how alterations to the Mekong hydrology could affect the Tonle Sap ecosystem. The following studies were performed to addressed the objective: (1) an assessment of landscape patterns using geographical information and remote sensing tools; (2) an assessment of habitat patterns based on field surveys of water, vegetation, and soils; (3) ecosystem function modelling to simulate net primary production (NPP) as a function of water quantity, sediments, and habitat type; and (4) fauna habitat modelling linking the results from the assessment of landscape patterns to fauna species. The assessment of landscape patterns revealed a distinct relationship between inundation and vegetation. Habitats in the Tonle Sap were divided into five groups based on annual flood duration, as well as physiognomic factors and human activity: (1) open water, (2) gallery forest, (3) seasonally flooded habitats, (4) transitional habitats, and (5) rainfed habitats. Large habitat shifts could occur as a result of hydropower development scenarios by the 2030s; areas optimal for gallery forest could decrease by 82% from baseline conditions, whereas areas of rainfed habitats could increase by 10-13 % (813-1061 km2). The assessment of habitat patterns demonstrated that despite the complexity and intense human use of this ecosystem, the flood-pulse is the underlying driver of habitat characteristics by (1) determining inundation depth and duration; (2) creating the main soils gradient; (3) limiting the area cleared for agriculture; (4) influencing vegetation structure and water quality; and (5) shaping the composition of plant species. The ecosystem function model was used to estimate a reduction of 9-39% in annual NPP caused by different scenarios of hydropower development and/or climate change during 2032-2042. Cumulative impacts from hydropower would disrupt NPP to a greater extent than climate change. The fauna habitat model revealed that species richness was greatest in the gallery forests and seasonally flooded habitats. Animals that permanently reside in or that rely on these habitats to complete essential life-history stages would be the most affected by future changes. This thesis provides the first quantitative formulation that directly links fundamental components of the Tonle Sap ecosystem to its flood-pulse hydrology. It also provides a comprehensive assessment of the impacts of expected hydrological alterations. Hydropower is expected to bring more abrupt and distinct ecological alterations than climate change in future decades. Relative aerial changes to the gallery forests are expected to be greater than in other habitats. A decline of the Tonle Sap’s ecosystem services will occur if appropriate measures are not implemented. These measures include mitigating hydropower alterations, conserving natural habitats in areas that are likely to remain hydrologically undisturbed, restoring natural habitats in projected areas for optimal growth, and optimizing agricultural practices in the floodplain. Research findings from this thesis focused on the Tonle Sap, but given the fundamental commonalities between this system and other large floodplains, the information presented is highly informative to other large flood-pulse driven systems around the globe.