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In this study, we applied a stepped-combustion approach to dating post-bomb lake sediment from north-central Mississippi. Samples were combusted at a low temperature (400 °) and then at 900 °. The CO2was collected separately for both... more
In this study, we applied a stepped-combustion approach to dating post-bomb lake sediment from north-central Mississippi. Samples were combusted at a low temperature (400 °) and then at 900 °. The CO2was collected separately for both combustions and analyzed. The goal of this work was to develop a methodology to improve the accuracy of14C dating of sediment by combusting at a lower temperature and reducing the amount of reworked carbon bound to clay minerals in the sample material. The14C fraction modern results for the low and high temperature fractions of these sediments were compared with well-defined137Cs determinations made on sediment taken from the same cores. Comparison of “bomb curves” for14C and137Cs indicate that low temperature combustion of sediment improved the accuracy of14C dating of the sediment. However, fraction modern results for the low temperature fractions were depressed compared to atmospheric values for the same time frame, possibly the result of carbon mixi...
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ABSTRACT Due to fragmentized terrain and physiognomy of typical loess landform, long-term anthropogenic influences, and inherent vulnerability, soil erosion is a serious problem in the Loess Plateau of China. There is a critical need to... more
ABSTRACT Due to fragmentized terrain and physiognomy of typical loess landform, long-term anthropogenic influences, and inherent vulnerability, soil erosion is a serious problem in the Loess Plateau of China. There is a critical need to assess soil erosion and spatial distribution for achieving sustainable land use and comprehensive soil conservation management. Taking the Yangou watershed as a case and using the Landsat Thematic Mapper image (land use map), Digital Elevation Model (DEM), soil maps, and precipitation data, this study integrated the revised universal soil loss equation (RUSLE) with GIS technology to estimate soil loss and its spatial distribution. The benefits of soil conservation of land use types were analyzed and the measures for future soil conservation planning were discussed. The results show that silt-covered land and terrace have high benefits of soil conservation, indicating that building check dam, producing silt-covered land for farming, and converting sloped farmland to terrace are effective ways to control soil erosion in the Yangou watershed. Furthermore, increasing vegetation coverage on lower coverage grassland, especially on the slopes with gradients >25°, and eliminating human disturbance in barren areas are feasible and effective measures for soil conservation planning. This study reveals that the integrated RUSLE-GIS model can evaluate and map soil erosion quantitatively and spatially at watershed scale in the Loess Plateau of China. The findings suggest strategies for coping with future soil conservation planning and provide valuable references for future assessments both in the Loess Plateau of China and elsewhere.
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Page 37. Effects of Emergent Riparian Vegetation on Spatially Averaged and Turbulent Flow Within an Experimental Channel Sean J. Bennett US Department of Agriculture-Agricultural Research Service, National Sedimentation ...
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The establishment of Total Maximum Daily Loads (TMDL) for contaminants entering water bodies requires the development of suitable methods for contaminant measurement. In an effort to assess quantities of suspended-sediment transport, an... more
The establishment of Total Maximum Daily Loads (TMDL) for contaminants entering water bodies requires the development of suitable methods for contaminant measurement. In an effort to assess quantities of suspended-sediment transport, an acoustic device is being developed in a ...
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Since 1948, the USDA-NRCS has constructed nearly 11,000 flood control dams across the United States, and many of the reservoirs are rapidly filling with sediment. To rehabilitate these structures, the impounded sediment must be assessed... more
Since 1948, the USDA-NRCS has constructed nearly 11,000 flood control dams across the United States, and many of the reservoirs are rapidly filling with sediment. To rehabilitate these structures, the impounded sediment must be assessed to determine the volume of accumulated sediment and the potential hazard this sediment may pose if reintroduced to the environment. An assessment of sedimentation issues
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Research Interests: Environmental Engineering, Civil Engineering, Water resources, Applied Economics, Model validation, and 10 moreSediment transport, Root-Mean Square Error, Suspended Sediment, Riparian vegetation, Numerical Model, Finite Volume Method, Sediment Transport, Experimental Data, Large Woody Debris, and Transport Equation
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River restoration that can be accomplished by structural and nonstructural means is one of the most important and popular recent advances in river engineering. Stream restoration techniques generally focus on protecting or restoring... more
River restoration that can be accomplished by structural and nonstructural means is one of the most important and popular recent advances in river engineering. Stream restoration techniques generally focus on protecting or restoring aquatic, riparian, and floodplain ...
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Visual-based rapid assessment techniques provide an efficient method for characterizing the restoration potential of streams, with many focusing on channel stability and instream habitat features. Few studies, however, have compared these... more
Visual-based rapid assessment techniques provide an efficient method for characterizing the restoration potential of streams, with many focusing on channel stability and instream habitat features. Few studies, however, have compared these techniques to see if they result in differing restoration priorities. Three rapid assessment techniques were contrasted at three wild trout streams in western New York with different amounts of channel disturbance. Two methods focused only on geomorphic stability, whereas the third addressed physical habitat condition. Habitat assessment scores were not correlated with scores for either geomorphic assessment method and they varied more between channels with different degrees of disturbance. A model based on dynamic equilibrium concepts best explains the variation among the streams and techniques because it accounts for a stream's capacity to maintain ecological integrity despite some inherent instability. Geomorphic indices can serve as effective proxies for biological indices in highly disturbed systems. Yet, this may not be the case in less disturbed systems, where geomorphic indices cannot differentiate channel adjustments that impact biota from those that do not. Dynamically stable streams can include both stable and unstable reaches locally as characterized by geomorphic methods and translating these results into restoration priorities may not be appropriate if interpretations are limited to the reach scale.
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... the test section. ~ : l-In(S/ (2a) \Yo/ ~-~ = U.2p (2b) where U. is shear velocity, K is the yon furman coefficient, yis the distance from the bed corresponding to velocity U, andYo is the zero-velocity roughness height. Because all... more
... the test section. ~ : l-In(S/ (2a) \Yo/ ~-~ = U.2p (2b) where U. is shear velocity, K is the yon furman coefficient, yis the distance from the bed corresponding to velocity U, andYo is the zero-velocity roughness height. Because all flows ...
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Page 1. Journal of Hydraulic Research Vol. 44, No. 4 (2006), pp. 510521 © 2006 International Association of Hydraulic Engineering and Research Turbulent flow and bed pressure within headcut scour holes due to plane reattached jets ...
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Surface Wave Forces Acting on Submerged Logs. [Journal of Hydraulic Engineering 128, 349 (2002)]. Nicholas P. Wallerstein, Carlos V. Alonso, Sean J. Bennett, Colin R. Thorne. Abstract. Drag forces exerted on cylindrical simulated ...
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The presence of sand moving at low transport rates over a flat bed modulates the production of turbulence when compared to clearwater flow at similar mean flow conditions. Phase Doppler anemometry is used to discriminate the turbulence... more
The presence of sand moving at low transport rates over a flat bed modulates the production of turbulence when compared to clearwater flow at similar mean flow conditions. Phase Doppler anemometry is used to discriminate the turbulence characteristics of the carrier fluid from ...
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... Francisco J. Jiménez-Hornero1,∗, , Juan V. Giráldez1, Ana M. Laguna2, Sean J. Bennett3 andCarlos V. Alonso4 ... Correspondence to: Francisco J. Jiménez-Hornero, Albert Einstein (C2) Building, Campus Rabanales, University of Cordoba,... more
... Francisco J. Jiménez-Hornero1,∗, , Juan V. Giráldez1, Ana M. Laguna2, Sean J. Bennett3 andCarlos V. Alonso4 ... Correspondence to: Francisco J. Jiménez-Hornero, Albert Einstein (C2) Building, Campus Rabanales, University of Cordoba, Cordoba 14071, Spain. ...
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ABSTRACT The fluid dynamics of a water jet impinging on a flat surface in confined conditions were studied using particle image velocimetery. The experiments were meant to replicate conditions expected in a jet erosion test (JET) designed... more
ABSTRACT The fluid dynamics of a water jet impinging on a flat surface in confined conditions were studied using particle image velocimetery. The experiments were meant to replicate conditions expected in a jet erosion test (JET) designed to assess cohesive sediment erosion parameters in field applications. High-resolution two-dimensional velocity vectors were measured in a plane passing the jet centerline including free jet, impingement, and wall jet regions within a fixed-wall box. The general flow behavior in the free jet and wall jet regions is in good agreement with the behavior of impinging jets in an unconfined environment. Results show that the entrainment coefficient, however, is lower than values in unconfined conditions, lowering lateral spreading rates. The rate of momentum transfer also increases along the axial direction since the confinement causes secondary flow and recirculation in the box. Wall shear stress is calculated based on extrapolation of Reynolds shear stress and turbulent kinetic energy, where the latter procedure provides more consistent results with expected scour hole shape under an impinging jet. This wall shear stress distribution shows higher values near jet impingement in comparison to previously reported distributions, especially as formulated for the JET under unconfined conditions. The maximum value of wall shear stress is found to be about 2.4 times greater than the commonly accepted value in the literature, and also occurs at a position closer to the impingement point. The shear stress at the impingement point is also close to its maximum value, which is consistent with the expected scour hole shape beneath an impinging jet. These findings have important implications for the use of jet impingement theory to assess sediment erosion, especially in the application of the JET.