The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Adrian M. Harvey - One of the best experts on this subject based on the ideXlab platform.
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The influence of sediment supply on the Channel Morphology of upland streams: Howgill Fells, Northwest England
Earth Surface Processes and Landforms, 1991Co-Authors: Adrian M. HarveyAbstract:Previous work on stream Channels in upland areas of Britain has demonstrated a close control over Channel Morphology and stability by the rate of coarse sediment supply from the hillslopes of the catchment. Streams fed by large amounts of coarse sediment develop unstable, wide, often braided Channels, whereas those with limited coarse sediment supply develop stable, much narrower, often meandering Channels. The sediment supply from hillslopes is controlled by thresholds of hillslope stability, storm event frequency, and the coupling between the hillslopes and the Channel. Climatically-induced changes in any of these three factors may have implications for Channel Morphology and stability. This paper examines these implications in British upland fluvial systems, with particular reference to the Howgill Fells, Cumbria, in the contexts of the adjustment of stream Channels to sediment supply from erosional gully systems, and their response to and recovery from major flood events.
Devi Datt Chauniyal - One of the best experts on this subject based on the ideXlab platform.
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Impact of Dam on Channel Morphology of Alaknanda River in Srinagar Valley (Garhwal Himalaya)
Himalayan Journal of Social Sciences and Humanities, 2019Co-Authors: Sapna Semwal, Devi Datt ChauniyalAbstract:Rivers play a significant role in the human activities all over the world. Increasing demand of water for drinking & irrigation and hydroelectricity, numbers of impacts can be seen in the rivers environment. The present paper focuses on the impact of Supana Dam on the Channel Morphology of Alaknanda River in Srinagar valley Garhwal Himalaya. The field investigation approach has been adopted for the present study. The impact assessment has been carried out into three categories i.e. (i) Impact of dam on Channel Morphology, (ii) Impact of dam on human environment and (iii) Anthropogenic impact on Channel Morphology. The results of the study show that after the construction of dam positive and negative impact have been assessed. Due to the blockage of water and sediment flow the entire riverine environment has been changed. Channel morphological features are well exposed for geomorphological study. Changing pattern of land and water relationship destroyed the previous ecosystem balance. Besides this, dam is supplying cheapest clean, efficient and reliable energy generated by hydroelectric power plant. Other impacts of dam are loss of fauna and flora, quality of drinking water supply and concentration of pollution in downstream. Out of these large numbers of sand and gravel extraction activities has been started on the exposed Channel bed. Although some positive and negative impacts are observed by the construction of dams but several measures have been suggested to mitigate the adverse impacts of a hydropower project in the present study area.
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Changing Pattern of Channel Morphology of Alaknanda River in Srinagar Valley (Garhwal Himalaya), India
Journal of the Indian Society of Remote Sensing, 2018Co-Authors: Devi Datt Chauniyal, Surajit Dutta, Sapna SemwalAbstract:The Alaknanda River is the most significant parental river of Ganga and forms an 11.5 km long and 2.5 km wide valley, locally known as the Srinagar Valley. The purpose of the present study is to highlight the recent landform changes in the Alaknanda Channel course after the Kedarnath disaster, 2013. The Kedarnath flood completely changed the Channel Morphology of the Alaknanda river. The river changed its course at Srikot, SSB and Sriyantra Tapu with lower terraces being silted by sands at Ranihat, SSB, Bhaktiyana and Sriyantra Tapu. A new depositional terrace also formed opposite to Sriyantra Tapu. New lateral Channel bars, braided Channels, back swamp, rapids, pools and river souls were identified in the Channel course of the river. Shifting of the Channel course at Chauras still remains a serious problem for the Garhwal University Chauras Campus. About 2–5 m silt was deposited on the lower terrace at SSB, and ITI. The Srikot river bed was appended to 4.60 m. Shifting of Channel course remains a serious threat to the Srinagar valley. Urbanization, sand and boulders mining, construction of dam, hydrological canal, road and settlements are the prominent example of anthropogenic activities which affect the shifting Channel.
Sapna Semwal - One of the best experts on this subject based on the ideXlab platform.
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Impact of Dam on Channel Morphology of Alaknanda River in Srinagar Valley (Garhwal Himalaya)
Himalayan Journal of Social Sciences and Humanities, 2019Co-Authors: Sapna Semwal, Devi Datt ChauniyalAbstract:Rivers play a significant role in the human activities all over the world. Increasing demand of water for drinking & irrigation and hydroelectricity, numbers of impacts can be seen in the rivers environment. The present paper focuses on the impact of Supana Dam on the Channel Morphology of Alaknanda River in Srinagar valley Garhwal Himalaya. The field investigation approach has been adopted for the present study. The impact assessment has been carried out into three categories i.e. (i) Impact of dam on Channel Morphology, (ii) Impact of dam on human environment and (iii) Anthropogenic impact on Channel Morphology. The results of the study show that after the construction of dam positive and negative impact have been assessed. Due to the blockage of water and sediment flow the entire riverine environment has been changed. Channel morphological features are well exposed for geomorphological study. Changing pattern of land and water relationship destroyed the previous ecosystem balance. Besides this, dam is supplying cheapest clean, efficient and reliable energy generated by hydroelectric power plant. Other impacts of dam are loss of fauna and flora, quality of drinking water supply and concentration of pollution in downstream. Out of these large numbers of sand and gravel extraction activities has been started on the exposed Channel bed. Although some positive and negative impacts are observed by the construction of dams but several measures have been suggested to mitigate the adverse impacts of a hydropower project in the present study area.
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Changing Pattern of Channel Morphology of Alaknanda River in Srinagar Valley (Garhwal Himalaya), India
Journal of the Indian Society of Remote Sensing, 2018Co-Authors: Devi Datt Chauniyal, Surajit Dutta, Sapna SemwalAbstract:The Alaknanda River is the most significant parental river of Ganga and forms an 11.5 km long and 2.5 km wide valley, locally known as the Srinagar Valley. The purpose of the present study is to highlight the recent landform changes in the Alaknanda Channel course after the Kedarnath disaster, 2013. The Kedarnath flood completely changed the Channel Morphology of the Alaknanda river. The river changed its course at Srikot, SSB and Sriyantra Tapu with lower terraces being silted by sands at Ranihat, SSB, Bhaktiyana and Sriyantra Tapu. A new depositional terrace also formed opposite to Sriyantra Tapu. New lateral Channel bars, braided Channels, back swamp, rapids, pools and river souls were identified in the Channel course of the river. Shifting of the Channel course at Chauras still remains a serious problem for the Garhwal University Chauras Campus. About 2–5 m silt was deposited on the lower terrace at SSB, and ITI. The Srikot river bed was appended to 4.60 m. Shifting of Channel course remains a serious threat to the Srinagar valley. Urbanization, sand and boulders mining, construction of dam, hydrological canal, road and settlements are the prominent example of anthropogenic activities which affect the shifting Channel.
Tim Davies - One of the best experts on this subject based on the ideXlab platform.
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Effects of land use on the Channel Morphology of streams in the Moutere Gravels, Nelson, New Zealand
Journal of hydrology. New Zealand, 2002Co-Authors: Brenda R. Baillie, Tim DaviesAbstract:Land use can affect Channel Morphology, especially in small catchments (up to 5-8 km2). Previous studies have suggested that stream Channels in pasture catchments are usually narrower than those in forested catchments due to the erosional resistance of grass, and its ability to trap and retain sediment. In the Hakarimata Ranges, Waikato, New Zealand, where the bedrock is predominantly sandstone, siltstone and mudstone, streams in small catchments converted from pasture to pine plantations are in the process of widening back to a forest Channel Morphology, releasing the sediment retained in the banks by the grass sod. As the majority of new pine plantations are on pastureland or reverting pastureland, the possibility of increased sedimentation in streams during this conversion process may be a problem in some areas. The Moutere Gravels in Nelson provide an area of contrasting geology, hydrology and climate to the Hakarimata Ranges for assessing the influence of land use on Channel Morphology. This study compared Channel Morphology characteristics in 15 streams in small-sized catchments, with 5 stream catchments each in pasture, pine plantation and native forest. There were no significant differences in bankfull width, Channel width, Channel depth and cross-sectional area of streams in catchments with the three types of land use in the Moutere Gravels. However, width-to-depth ratios were significantly higher in the pasture streams than in the forest streams, median particle size was significantly lower in the pasture and pine plantation sites than in the native forest sites and there were more pools in the forest streams, in part attributable to the presence of woody debris. It is suggested that low sediment yields, infrequent floods of sufficient magnitude to influence Channel Morphology, and the cohesive Channel bank material in the Moutere Gravels may explain the lack of effects of land use on Channel Morphology in these small catchments. The results from the Moutere Gravels suggest that factors other than land use can sometimes exert a stronger influence on Channel Morphology in small catchments.
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Influence of large woody debris on Channel Morphology in native forest and pine plantation streams in the Nelson region, New Zealand
New Zealand Journal of Marine and Freshwater Research, 2002Co-Authors: Brenda R. Baillie, Tim DaviesAbstract:Abstract The influence of large woody debris (LWD) on Channel Morphology was assessed in five pine plantation and five native forest streams in the Nelson region of New Zealand. LWD volumes averaged 127 m3 ha–1 in pine plantation streams and 94 m3 ha–1 in native forest streams. Most of the LWD in pine and native streams had no influence on Channel Morphology (78 and 54%, respectively). Those LWD pieces influencing Channel Morphology contributed mainly to sediment storage in both pine and native streams as well as flow deflection and debris collection in the native streams. Wood aligned either perpendicular or obliquely to stream flow and positioned on or partly buried in the stream bed had the greatest influence on Channel Morphology. There were twice as many pools in native streams as in pine streams, and scour processes formed the majority of pools. LWD influenced c. 50% of pool formation in both pine and native streams and increased pool variety. LWD volumes in these streams are low compared with Pacif...
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Variability of bedload transport and Channel Morphology in a braided river hydraulic model
Earth Surface Processes and Landforms, 1994Co-Authors: Jeff Warburton, Tim DaviesAbstract:This paper investigates variability in bedload transport and Channel Morphology for 11 replicate experimental runs in an approximately 1:50 braided river model. The experiments, each of 90 h duration, were carried out in a 20 × 3m tilting flume. All the experiments started with the same initial conditions. Bedload transport was measured at 5 min intervals in a collection drum at the exit from the flume. The model showed reasonable hydraulic similarity when compared to prototype rivers. Results show that mean bedload transport rates for the 11 runs vary in the range 0·98 to 1·49gs−1 (mean + 1·21, coefficient of variation 11 per cent). Within-run transport rates commonly vary from close to zero, to two and occasionally three or four times the mean rate. Within the bedload series, several irregular phases of transport intensity can be observed, but time series analysis of the data show little underlying serial structure (an AR(2) autoregressive model is appropriate). Channel patterns are narrow/braided, are established quickly and remain relatively stable throughout the runs, although Channel widths increase between 20 and 103 per cent over the 11 runs. Channel behaviour varies from aggradational to transitional between aggradation and degradation. Time-averaged bedload transport rate is weakly correlated with braiding intensity. In general, these results demonstrate that for a given set of controlling variables, bedload transport and Channel Morphology can be approximately replicated.
Kun Zhou - One of the best experts on this subject based on the ideXlab platform.
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Channel Morphology effect on water transport through graphene bilayers.
Scientific reports, 2016Co-Authors: Bo Liu, Adrian Wing-keung Law, Xi-qiao Feng, Lichun Bai, Kun ZhouAbstract:The application of few-layered graphene-derived functional thin films for molecular filtration and separation has recently attracted intensive interests. In practice, the Morphology of the nanoChannel formed by the graphene (GE) layers is not ideally flat and can be affected by various factors. This work investigates the effect of Channel Morphology on the water transport behaviors through the GE bilayers via molecular dynamics simulations. The simulation results show that the water flow velocity and transport resistance highly depend on the curvature of the graphene layers, particularly when they are curved in non-synergic patterns. To understand the Channel Morphology effect, the distributions of water density, dipole moment orientation and hydrogen bonds inside the Channel are investigated, and the potential energy surface with different distances to the basal GE layer is analyzed. It shows that the Channel Morphology significantly changes the distribution of the water molecules and their orientation and interaction inside the Channel. The energy barrier for water molecules transport through the Channel also significantly depends on the Channel Morphology.
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Keynote: Tuning water transport in graphene layers via Channel Morphology modification
2016Co-Authors: Bo Liu, Adrian Wing-keung Law, Xi-qiao Feng, Kun ZhouAbstract:Recently, the application of few-layered graphene-derived functional thin films for molecular filtration and separation has attracted intensive interests due to their unique lamellar porous microstructures. Different from the single layer graphene (GE) with elaborately created nanopores, in the layered GE-derived thin films, molecules with appropriate sizes permeate through the interconnected nanoChannels formed between adjacent GE layers. Compared with the nanopores in the single layer GE, these nanoChannels allow fast molecule transport and their sizes can also be efficiently controlled for flexible filtration tunability . In practice, the Morphology of the nanoChannel formed by the GE layers is affected by various factors. For example, during the fabrication of GE thin films by vacuum filtration or spin coating from GE oxide solution, small GE flakes can fold and lie between two other large flakes. In this scenario, the nanoChannel becomes asperous. In addition, residual chemical functional groups would also exist in the space of adjacent GE layers, and thus change the shape of the nanoChannel. With the change of the Morphology of the nanoChannel, the water transport behaviors inside it would deviate significantly from those observed in ideally flat GE layers and should be understood. Hence, in this study, the effect of Channel Morphology on the water transport behaviors through the graphene (GE) bilayers has been investigated via molecular dynamics simulations. The Morphology of the Channel is modified by applying deformation to the GE layers along the Channel thickness direction in a sinusoidal wave profile. The simulation results show that the water flow velocity and transport resistance highly depend on the wave amplitude, period length and the phase angle difference between the two GE layers. To understand the Channel Morphology effect, the distributions of water density, dipole moment orientation and hydrogen bonds inside the Channel have been investigated, and the potential energy surface with different distances to the basal GE layer has also been analyzed. It is demonstrated that the Channel Morphology significantly changes the distribution of the water molecules and their orientation and interaction inside the Channel. The energy barrier for water molecules transport through the Channel also significantly depends on the Channel Morphology. The results obtained in the present study are helpful for the understanding of the water transport in nanoconfiments particularly with the effect of Morphology of the confining walls being taken into account. As the potential value of multilayer GE-based membranes in the applications of nanofiltration is being more and more recognized, this study is of significance to provide guidance for the design and application of such GE-based membranes in future nanofiltration and water purification technologies.