Impact of Different Vegetation Zones on the Velocity and Discharge of Open-Channel Flow

Different types of vegetation widely exist in rivers and wetlands. The vegetation will affect the ecological environment and flow process, thus becoming increasingly significant in river engineering and aquatic environmental management. Previous research on vegetated flow is mainly to understand the flow structure of open channels with fully covered one-layer vegetation. However, vegetation often grows along a river bank and co-exists in different heights. The present paper presents experimental results about the flow characteristics of an open-channel with two sides covered by differently layered vegetation, focusing on the effect of vegetation on the velocity distribution and discharge. Two heights of dowels in 10 cm and 20 cm were used to simulate rigid vegetation and arranged in a linear form on both sides of a channel bed under emergent and fully submerged flow conditions. The velocity at different positions was obtained using ADV (Acoustic Doppler Velocimetry). Measured results demonstrate that there exists a shear layer between free-flow and vegetated zones, indicating that the flow transition occurs between fast-moving flow in the free zone and slowly obstructed flow in the vegetated zone and induces a high shear layer and transverse coherent vortices near the interface. Furthermore, compared with the emergent condition, the discharge through the free-flow region slightly decreases under full submerged conditions while the discharge in the vegetated region increases, indicating that the vegetation does not significantly change the discharge percentage in the free region. These findings on differently-layered vegetation would help riparian management practices to maintain healthy ecological and habitat zones.

Identifying Factors That Influence Accuracy of Riparian Vegetation Classification and River Channel Delineation Mapped Using 1 m Data

Riparian vegetation delineation includes both the process of delineating the riparian zone and classifying vegetation within that zone. We developed a holistic framework to assess riparian vegetation delineation that includes evaluating channel boundary delineation accuracy using a combination of pixel- and object-based metrics. We also identified how stream order, riparian zone width, riparian land use, and image shadow influenced the accuracy of delineation and classification. We tested the framework by evaluating vegetation vs. non-vegetation riparian zone maps produced by applying random forest classification to aerial photographs with a 1 m pixel size. We assessed accuracy of the riparian vegetation classification and channel boundary delineation for two rivers in the northeastern United States. Overall accuracy for the channel boundary delineation was generally above 80% for both sites, while object-based accuracy revealed that 50% of delineated channel was less than 5 m away from the reference channel. Stream order affected channel boundary delineation accuracy while land use and image shadows influenced riparian vegetation classification accuracy; riparian zone width had little impact on observed accuracy. The holistic approach to quantification of accuracy that considers both channel boundary delineation and vegetation classification developed in this study provides an important tool to inform riparian management.

Dairy Industry under New Zealand's Emissions Trading Scheme: Analysis of Farmers' Attitudes towards Climate Change: The Expense Created by the NZETS and the Point that Farmers will Begin to Reduce Emissions

<p>Adaptation to actual climate change and contingency planning to reduce vulnerability from likely climate change effects is crucial for the New Zealand dairy industry. Thus in alignment with international treaties and growing international pressure and speculation, the New Zealand Government in October 2007 announced an Emissions Trading Scheme (ETS) adaptable specifically to the New Zealand scene. This ETS passed into law in September 2008 through the enactment of the Climate Change Response (Emissions Trading) Amendment Act 2008. This thesis specifically looks at agriculture related emissions and calculates the liability faced by the dairy industry come 2013 when the industry is completely involved in the ETS. The purpose of this is to further aid the industry so that it can best align itself with the ETS in order to minimise this liability. This is not simply an aid to help the industry save money, as the minimisation of liability should come as a benefit to the environment through reduced emissions. There is also a second issue associated with this - as to whether the liability faced by the industry will be material enough in order for the farmers to actually mitigate their environmental impacts or will they simply bear the expense and ignore the opportunities to reduce their emissions against a baseline (and potentially generate carbon credits for sale) and/or offset any residual emissions through purchasing carbon credits? This therefore analysed the threshold of farmer's incomes whereby they will choose to abate their emissions rather than simply paying for their carbon emissions liability. This threshold obviously varied greatly through the dairying industry with differing factors - this was taken into account and discussed in detail. Other aspects influence this threshold also, factors such as the opportunity for the industry to market a niche product if they do achieve a low carbon or carbon neutral status for their products, cost competitiveness of available abatement technologies, geographical issues pertaining to each abatement method and so on. In order to gain an insight into farmers' perceptions 23 Taranaki dairy farmers were interviewed. This 23 was selected randomly from a list of farmers who reside in the geographical area of Taranaki. This randomisation allowed for an analysis of a variety of size of farmers which eliminated a bias of perceptions from dominating farming sizes within this region. Utilising the theoretical framework surrounding stabilisation triangles, riparian management and nitrification inhibitors were the basis of this examination for emissions reduction management due to their major co-benefit of improved water quality alongside the ultimate goal of emissions reductions. The extent of potential mitigation through the implementation of riparian management and nitrification inhibitors equates to two of the wedges required for the overall reduction in emissions under the ETS. Also, as explained earlier, the co-benefit of improved water quality associated with riparian management and nitrification inhibitors make their implementation even more attractive. The theory behind riparian management and nitrification inhibitors has mostly been done, therefore for the purpose of this thesis, farmers' perceptions of the abatement options were examined. These perceptions included the associated opportunities as well as the challenges that will be faced by those participating farmers.</p>

Dairy Industry under New Zealand's Emissions Trading Scheme: Analysis of Farmers' Attitudes towards Climate Change: The Expense Created by the NZETS and the Point that Farmers will Begin to Reduce Emissions

<p>Adaptation to actual climate change and contingency planning to reduce vulnerability from likely climate change effects is crucial for the New Zealand dairy industry. Thus in alignment with international treaties and growing international pressure and speculation, the New Zealand Government in October 2007 announced an Emissions Trading Scheme (ETS) adaptable specifically to the New Zealand scene. This ETS passed into law in September 2008 through the enactment of the Climate Change Response (Emissions Trading) Amendment Act 2008. This thesis specifically looks at agriculture related emissions and calculates the liability faced by the dairy industry come 2013 when the industry is completely involved in the ETS. The purpose of this is to further aid the industry so that it can best align itself with the ETS in order to minimise this liability. This is not simply an aid to help the industry save money, as the minimisation of liability should come as a benefit to the environment through reduced emissions. There is also a second issue associated with this - as to whether the liability faced by the industry will be material enough in order for the farmers to actually mitigate their environmental impacts or will they simply bear the expense and ignore the opportunities to reduce their emissions against a baseline (and potentially generate carbon credits for sale) and/or offset any residual emissions through purchasing carbon credits? This therefore analysed the threshold of farmer's incomes whereby they will choose to abate their emissions rather than simply paying for their carbon emissions liability. This threshold obviously varied greatly through the dairying industry with differing factors - this was taken into account and discussed in detail. Other aspects influence this threshold also, factors such as the opportunity for the industry to market a niche product if they do achieve a low carbon or carbon neutral status for their products, cost competitiveness of available abatement technologies, geographical issues pertaining to each abatement method and so on. In order to gain an insight into farmers' perceptions 23 Taranaki dairy farmers were interviewed. This 23 was selected randomly from a list of farmers who reside in the geographical area of Taranaki. This randomisation allowed for an analysis of a variety of size of farmers which eliminated a bias of perceptions from dominating farming sizes within this region. Utilising the theoretical framework surrounding stabilisation triangles, riparian management and nitrification inhibitors were the basis of this examination for emissions reduction management due to their major co-benefit of improved water quality alongside the ultimate goal of emissions reductions. The extent of potential mitigation through the implementation of riparian management and nitrification inhibitors equates to two of the wedges required for the overall reduction in emissions under the ETS. Also, as explained earlier, the co-benefit of improved water quality associated with riparian management and nitrification inhibitors make their implementation even more attractive. The theory behind riparian management and nitrification inhibitors has mostly been done, therefore for the purpose of this thesis, farmers' perceptions of the abatement options were examined. These perceptions included the associated opportunities as well as the challenges that will be faced by those participating farmers.</p>

Can Understory Plant Composition and Richness Help Designate Riparian Management Zones in Mesic Headwater Forests of the Northeastern United States?

Riparian buffers implemented to minimize sediment, nutrients, and disturbance impacts on streams during forest operations vary greatly in the degree to which ecological criteria are used in their design. Because most forest operations are concentrated around headwater streams, our primary research objective was to identify a floristically based riparian boundary for headwater streams using plant species composition and indicator species to classify riparian environments distinct from the surrounding upland forest. Within three forested regions of the Northeast US, understory vegetation plots were sampled along perpendicular transects extending from the stream bank into the upland forest. At all sites, species richness was highest adjacent to the stream, decreasing exponentially within 6–12 m from the channel. Species composition closest to the stream was significantly different from all other lateral distances, but identified riparian indicator species were of limited practical use across all sites. However, changes in species richness can serve to identify a riparian area extent up to 6–12 m from headwater streams. Study Implications Riparian areas around headwater streams can be sensitive to forest management activities, particularly harvesting. Riparian management zone (RMZ) buffers around these streams vary in the degree to which they are based on ecological criteria; for example, fixed-width buffers may or may not adequately protect the riparian area. Our study within three forests of the Northeast detected a significant exponential decreasing trend in understory plant species richness within 6–12 m (20–40 ft) from the stream bank. We believe this ecologically based floristic zone closest to the stream represents the most sensitive part of the RMZ. This study recommends a 12 m (40 ft) zone to maintain the majority of the forest cover and minimize the impact of logging equipment. Foresters should be cognizant of this 12 m zone when implementing silvicultural activities and planning harvest access systems.

Mapping Hydromorphic Areas and Drainage Networks in Tropical Riparian Zones using Topographic Attributes

Riparian areas and channel networks are important landscape compartments, with key hydrological and ecologic functions. Hence, defining their spatial boundaries is an important step towards sustainable riparian management. In tropical countries, riparian areas are rarely mapped, although they represent a crucial component of local livelihoods and ecosystems. In this study, topographic attributes generated with a 30m SRTM DEM were used to delineate wet areas and stream networks of two small catchments in Central Brazil. The topographic attributes were the local slope, the slope curvature, and the Topographic Wetness Index-TWI, respectively. Threshold values of the selected topographic attributes were calibrated in the Santa Maria catchment, comparing the synthetic wet areas and drainage networks with corresponding reference (map) features, and validated in the nearby Santa Maria basin. Drainage network and wet area delineation accuracies were estimated with multi-criteria and confusion matrix methods. The drainage network delineation accuracy was 67.2% and 70.7%, and wet area prediction accuracy was 72.7% and 73.8%, for the Santa Maria and Gama catchments, respectively. The delineation errors resulted from model incompleteness, DEM grid size and vertical inaccuracy, and from cartographic misrepresentation of the reference maps. The method performed equal or better than other studies in the literature, and could be used for preliminary mapping of riparian areas of tropical catchments.

Small Patches of Riparian Woody Vegetation Enhance Biodiversity of Invertebrates

Patches of riparian woody vegetation potentially help mitigate environmental impacts of agriculture and safeguard biodiversity. We investigated the effects of riparian forest on invertebrate diversity in coupled stream-riparian networks using a case study in the Zwalm river basin (Flanders, Belgium). Agriculture is one of the main pressures in the basin and riparian forest is limited to a number of isolated patches. Our 32 study sites comprised nine unshaded “unbuffered” sites which were paired with nine shaded “buffered” sites on the same stream reach, along with five ‘least-disturbed’ sites and nine downstream sites. We sampled water chemistry, habitat characteristics and stream and riparian invertebrates (carabid beetles and spiders) at each site. Three methods were used to quantify riparian attributes at different spatial scales: a visually-assessed qualitative index, quantitative estimates of habitat categories in six rectangular plots (10 × 5 m) and geographic information system (GIS)-derived land cover data. We investigated relationships between invertebrates and riparian attributes at different scales with linear regression and redundancy analyses. Spiders and carabids were most associated with local riparian attributes. In contrast, aquatic macroinvertebrates were strongly influenced by the extent of riparian vegetation in a riparian band upstream (100–300 m). These findings demonstrate the value of quantifying GIS-based metrics of riparian cover over larger spatial scales into assessments of the efficacy of riparian management as a complement to more detailed local scale riparian assessments in situ. Our findings highlight the value of even small patches of riparian vegetation in an otherwise extensively disturbed landscape in supporting biodiversity of both terrestrial and freshwater invertebrates and emphasize the need to consider multiple spatial scales in riparian management strategies which aim to mitigate human impacts on biodiversity in stream-riparian networks.

Forest riparian buffers reduce timber harvesting effects on stream temperature, but additional climate adaptation strategies are likely needed under future conditions

Stream water temperature imposes metabolic constraints on the health of cold-water fish like salmonids. Timber harvesting can reduce stream shading leading to higher water temperatures, while also altering stream hydrology. In the Pacific Northwest, riparian buffer requirements are designed to mitigate these impacts; however, anticipated future changes in air temperature and precipitation could reduce the efficacy of these practices in protecting aquatic ecosystems. Using a combined modeling approach (Soil and Water Assessment Tool (SWAT), Shade, and QUAL2K), this study examines the effectiveness of riparian buffers in reducing impacts of timber harvest on stream water temperature in Lookout Creek, Oregon across a range of potential future climates. Simulations assess changes in riparian management alone, climate alone, and combined effects. Results suggest that maximum stream water temperatures during thermal stress events are projected to increase by 3.3–7.4 °C due to hydroclimatic change alone by the end of this century. Riparian management is effective in reducing stream temperature increases from timber harvesting alone but cannot fully counteract the additional effects of a warming climate. Overall, our findings suggest that the protection of sensitive aquatic species will likely require additional adaptation strategies, such as the protection or provisioning of cool water refugia, to enhance survival during maximum thermal stress events.

Partnerships Generate Co-Benefits in Agricultural Stream Restoration (Canterbury, New Zealand)

In Aotearoa New Zealand, agricultural land-use intensification and decline in freshwater ecosystem integrity pose complex challenges for science and society. Despite riparian management programmes across the country, there is frustration over a lack in widespread uptake, upfront financial costs, possible loss in income, obstructive legislation and delays in ecological recovery. Thus, social, economic and institutional barriers exist when implementing and assessing agricultural freshwater restoration. Partnerships are essential to overcome such barriers by identifying and promoting co-benefits that result in amplifying individual efforts among stakeholder groups into coordinated, large-scale change. Here, we describe how initial progress by a sole farming family at the Silverstream in the Canterbury region, South Island, New Zealand, was used as a catalyst for change by the Canterbury Waterway Rehabilitation Experiment, a university-led restoration research project. Partners included farmers, researchers, government, industry, treaty partners (Indigenous rights-holders) and practitioners. Local capacity and capability was strengthened with practitioner groups, schools and the wider community. With partnerships in place, co-benefits included lowered costs involved with large-scale actions (e.g., earth moving), reduced pressure on individual farmers to undertake large-scale change (e.g., increased participation and engagement), while also legitimising the social contracts for farmers, scientists, government and industry to engage in farming and freshwater management. We describe contributions and benefits generated from the project and describe iterative actions that together built trust, leveraged and aligned opportunities. These actions were scaled from a single farm to multiple catchments nationally.