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181.
Saeed Khorram Mustafa Ergil 《Journal of the American Water Resources Association》2010,46(6):1065-1090
Khorram, Saeed and Mustafa Ergil, 2010. Most Influential Parameters for the Bed-Load Sediment Flux Equations Used in Alluvial Rivers. Journal of the American Water Resources Association (JAWRA): 46(6):1065–1090. DOI: 10.1111/j.1752-1688.2010.00468.x Abstract: Problems of bed-load sediment transport equations in alluvial rivers are addressed in this study where user-friendly parameters were developed. To determine the influences of 300 parameters on the final result, 52 selected bed-load equations for noncohesive particles (sand and gravel separately) were gathered and individually investigated. The influences of discrepancies among the computed and measured datasets were obtained by sensitivity analysis through multilinear regression method. The most influential parameters for the bed-load sediment flux equations used to describe sand particles in alluvial rivers are: the gravitational power due to Shields’ parameter with an energy slope, the universal stream power due to critical Shields’ parameter with an energy slope, the Shields’ parameter ratio, the critical unit stream power, and the Shields’ parameter with energy slope. For gravel particles, the most influential parameters are: the universal stream power due to critical Shields’ parameter with an energy slope, the Shields’ parameter ratio, the gravitational power due to Shields’ parameter with an energy slope, the Shields’ parameter with an energy slope, and the Froude number of the channel. It is expected that researchers working in this field will be able to use these predicted parameters to generate new bed-load sediment flux equations that give results that more closely agree with the actual values measured in alluvial rivers. 相似文献
182.
Jason M. Zink Gregory D. Jennings G. Alexander Price 《Journal of the American Water Resources Association》2012,48(4):762-773
Zink, Jason M., Gregory D. Jennings, and G. Alexander Price, 2012. Morphology Characteristics of Southern Appalachian Wilderness Streams. Journal of the American Water Resources Association (JAWRA) 48(4): 762‐773. DOI: 10.1111/j.1752‐1688.2012.00647.x Abstract: Watersheds without urbanization or impacts from logging are rare in the southern Appalachian Mountains. The Joyce Kilmer/Slickrock Wilderness of North Carolina and Tennessee contains 24 km2 of old‐growth forest, with the balance of the wilderness in a mature second‐growth forest. The watersheds of Little Santeetlah and Slickrock Creek are located within the wilderness. Morphological information, including channel dimensions and longitudinal profiles, was gathered from 14 alluvial stream reaches in these watersheds. The study sites had drainage areas from 0.25 to 41.6 km2 and stream slopes from 0.014 to 0.104 m/m. Bankfull cross‐section dimensions of the study stream reaches were strongly correlated to drainage area across the observed range of slopes and bed morphology. Cross‐section area and width relationships for the streams in this study did not differ significantly from regional curves for the mountain physiographic region of North Carolina. Observations of these reaches did not suggest a definitive rule regarding the proportion of steps and riffles in streams. Pools occupied greater than 50% of the length in all stream reaches with slopes less than 0.07 m/m. Significant correlation existed between step height ratio and slope, suggesting that step height can be approximated as the product of channel width and slope. Riffle length and riffle slope ratios were also significantly correlated with slope, though pool spacing was not. 相似文献
183.
John W. Brakebill Scott W. Ator Gregory E. Schwarz 《Journal of the American Water Resources Association》2010,46(4):757-776
Brakebill, John W., Scott W. Ator, and Gregory E. Schwarz, 2010. Sources of Suspended-Sediment Flux in Streams of the Chesapeake Bay Watershed: A Regional Application of the SPARROW Model. Journal of the American Water Resources Association (JAWRA) 46(4): 757-776. DOI: 10.1111/j.1752-1688.2010.00450.x Abstract: We describe the sources and transport of fluvial suspended sediment in nontidal streams of the Chesapeake Bay watershed and vicinity. We applied SPAtially Referenced Regressions on Watershed attributes, which spatially correlates estimated mean annual flux of suspended sediment in nontidal streams with sources of suspended sediment and transport factors. According to our model, urban development generates on average the greatest amount of suspended sediment per unit area (3,928 Mg/km2/year), although agriculture is much more widespread and is the greatest overall source of suspended sediment (57 Mg/km2/year). Factors affecting sediment transport from uplands to streams include mean basin slope, reservoirs, physiography, and soil permeability. On average, 59% of upland suspended sediment generated is temporarily stored along large rivers draining the Coastal Plain or in reservoirs throughout the watershed. Applying erosion and sediment controls from agriculture and urban development in areas of the northern Piedmont close to the upper Bay, where the combined effects of watershed characteristics on sediment transport have the greatest influence may be most helpful in mitigating sedimentation in the bay and its tributaries. Stream restoration efforts addressing floodplain and bank stabilization and incision may be more effective in smaller, headwater streams outside of the Coastal Plain. 相似文献
184.
Charles J.P. Podolak 《Journal of the American Water Resources Association》2013,49(2):390-401
Abstract: An ensemble of rule‐based models was constructed to assess possible future braided river planform configurations for the Toklat River in Denali National Park and Preserve, Alaska. This approach combined an analysis of large‐scale influences on stability with several reduced‐complexity models to produce the predictions at a practical level for managers concerned about the persistence of bank erosion while acknowledging the great uncertainty in any landscape prediction. First, a model of confluence angles reproduced observed angles of a major confluence, but showed limited susceptibility to a major rearrangement of the channel planform downstream. Second, a probabilistic map of channel locations was created with a two‐parameter channel avulsion model. The predicted channel belt location was concentrated in the same area as the current channel belt. Finally, a suite of valley‐scale channel and braid plain characteristics were extracted from a light detection and ranging (LiDAR)‐derived surface. The characteristics demonstrated large‐scale stabilizing topographic influences on channel planform. The combination of independent analyses increased confidence in the conclusion that the Toklat River braided planform is a dynamically stable system due to large and persistent valley‐scale influences, and that a range of avulsive perturbations are likely to result in a relatively unchanged planform configuration in the short term. 相似文献
185.
城市水环境控制单元污染物入河量估算方法 总被引:2,自引:1,他引:2
在资料不全且无法进行试验的地区,为了估算污染物进入目标水体的负荷,需要充分利用易获得的数据.使用污染源普查数据和土地利用数据,同时考虑距离对污染物入河过程的影响,来估算水环境控制单元内的污染物入河量.大辽河水环境控制单元营口段是以城区污染为主的城市水环境控制单元,以大辽河水环境控制单元营口段为例估算控制单元内污染物入河量,并进行分析.结果表明使用污染源普查数据和土地利用数据,在根据距离考虑入河系数的情况下能够较准确的估算出污染物入河量,可以为后期进行水环境容量核定工作提供基础数据,同时为城市规划管理者提供制定减排政策的依据. 相似文献
186.
John F. Joseph Hatim O. Sharif Jeffrey G. Arnold David D. Bosch 《Journal of the American Water Resources Association》2013,49(2):300-318
Abstract: The calibration of basin‐scale hydrologic models consists of adjusting parameters such that simulated values closely match observed values. However, due to inevitable inaccuracies in models and model inputs, simulated response hydrographs for multiyear calibrations will not be perfectly synchronized with observed response hydrographs at the daily time step. An analytically derived formula suggests that when timing errors are significant, traditional calibration approaches may generally underestimate the total event‐flow volume. An event‐adaptive time series is developed and incorporated into the Nash‐Sutcliffe Efficiency objective function to diagnose the potential impact of event‐flow synchronization errors. Test sites are the 50 km2 Subwatershed I of the Little River Experimental Watershed (LREWswI) in southeastern Georgia, and the 610 km2 Little Washita River Experimental Watershed (LWREW) in southwestern Oklahoma, with the Soil and Water Assessment Tool used as the hydrologic model. Results suggest that simulated surface runoff generation is 55% less for LREWswI when the daily time series is used compared with when the event‐adaptive technique is used. Event‐flow generation may also be underestimated for LWREW, but to a lesser extent than it may be for LREWswI, due to a larger portion of the event flow being lateral flow. 相似文献
187.
Sarah E. Null Scott T. Ligare Joshua H. Viers 《Journal of the American Water Resources Association》2013,49(6):1456-1472
This article provides a method for examining mesoscale water quality objectives downstream of dams with anticipated climate change using a multimodel approach. Coldwater habitat for species such as trout and salmon has been reduced by water regulation, dam building, and land use change that alter stream temperatures. Climate change is an additional threat. Changing hydroclimatic conditions will likely impact water temperatures below dams and affect downstream ecology. We model reservoir thermal dynamics and release operations (assuming that operations remain unchanged through time) of hypothetical reservoirs of different sizes, elevations, and latitudes with climate‐forced inflow hydrologies to examine the potential to manage water temperatures for coldwater habitat. All models are one dimensional and operate on a weekly timestep. Results are presented as water temperature change from the historical time period and indicate that reservoirs release water that is cooler than upstream conditions, although the absolute temperatures of reaches below dams warm with climate change. Stream temperatures are sensitive to changes in reservoir volume, elevation, and latitude. Our approach is presented as a proof of concept study to evaluate reservoir regulation effects on stream temperatures and coldwater habitat with climate change. 相似文献
188.
POST‐HARVEST RIPARIAN BUFFER RESPONSE: IMPLICATIONS FOR WOOD RECRUITMENT MODELING AND BUFFER DESIGN1
Michael K. Liquori 《Journal of the American Water Resources Association》2006,42(1):177-189
Despite the importance of riparian buffers in providing aquatic functions to forested streams, few studies have sought to capture key differences in ecological and geomorphic processes between buffered sites and forested conditions. This study examines post‐harvest buffer conditions from 20 randomly selected harvest sites within a managed tree farm in the Cascade Mountains of western Washington. Post‐harvest wind derived treefall rates in buffers up to three years post‐harvest averaged 268 trees/km/year, 26 times greater than competition‐induced mortality rate estimates. Treefall rates and stem breakage were strongly tied to tree species and relatively unaffected by stream direction. Observed treefall direction is strongly biased toward the channel, irrespective of channel or buffer orientation. Fall direction bias can deliver significantly more wood recruitment relative to randomly directed treefall, suggesting that models that utilize the random fall assumption will significantly underpredict recruitment. A simple estimate of post‐harvest wood recruitment from buffers can be obtained from species specific treefall and breakage rates, combined with bias corrected recruitment probability as a function of source distance from the channel. Post‐harvest wind effects may reduce the standing density of trees enough to significantly reduce or eliminate competition mortality and thus indirectly alter bank erosion rates, resulting in substantially different wood recruitment dynamics from buffers as compared to unmanaged forests. 相似文献
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190.