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1.
The paper presents an investigation of injection effects on the bedload transport rate. According to dimensional analysis, two dimensionless groups, an Einstein＇s parameter group and a modified densimetric Froude number group, were chosen to examine how injection affects the bedload transport rate. Experimental studies were conducted in an open-channel flume with an upward seepage zone. The sediment particles used for the test were 0.9 mm in diameter. The experimental results show that an increase in the injection velocity causes a reduction in the shear velocity excess, which is defined as the difference between the shear and critical shear velocities, leading to a reduction in the bedload transport rate. The equation for predicting the bedload transport rate in the presence of upward seepage was derived empirically. The proposed prediction method is suitable for engineering practice, since it only requires the undisturbed flow condition, properties of sediment particles, and the injection velocity. 相似文献
2.
Experimental Study of Sediment Transport in Meandering Channels 总被引：1，自引：1，他引：0
Levent Yilmaz 《Water Resources Management》2008,22(2):259-275
Sediment transport in a meandering channel is measured in a laboratory flume. The measurements are evaluated and compared with previous studies. The values of the calculated sediment transport rates using previous formulas are generally overestimated. Under these circumstances, in this research, it is noticed that the sediment transport rates as measured in the laboratory, and sediment transport capacities computed with the Einstein’s approach, behave in a quite similar way, seemingly closely related to the varying bottom shear velocity or stress. Einstein’s approach for bed load comparison is chosen in this experimental research because it has been tested to some extent. 相似文献
3.
Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base. 相似文献
4.
River channel substrate size and mobility are important to Atlantic salmon spawning and rearing success. We compare morphology and bed sediment between two North American Atlantic coastal streams (Narraguagus River, Maine, USA and Jacquet River, New Brunswick, Canada). The watersheds have similar drainage areas and mean annual precipitation, but differing relief structure, channel longitudinal profiles and numbers of returning salmon. The lower‐relief Narraguagus River is segmented into steeper (gradient >0.002) and flatter reaches (gradient <0.0005). Flat reaches, including mainstem lakes, act as sediment sinks, preventing the continuity of downstream sediment transport. Based on field measurements, the Narraguagus River has a larger high‐flow width to depth ratio than the Jacquet River, but this difference is principally the result of outliers from low‐gradient channel reaches. Measurements of substrate grain size reveal finer river‐bed sediments on the Narraguagus River, however, Shields parameter calculations indicate that bed sediment should be mobile during high flows in both streams. We use the Shields equation to predict grain size based on channel slope, width and drainage area measured from digital elevation models (DEM) and aerial photographs. Predictions of median grain size agree with field measurements within a factor of 2 for 62–70% of the survey stations. We suggest ways that model misfits may provide opportunities to prioritize reach‐based restoration efforts. Based on expected grain size, we estimate 62% spawning and 68% rearing habitat along the length of the Narraguagus River, and 28 and 95% respectively on the Jacquet. Overall, glacial history and relief structure appear to be the first‐order controls on substrate grain size and habitat quality in these two rivers. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
坡面薄层水流侵蚀试验研究及土壤抗冲性评价 总被引：12，自引：0，他引：12
通过室内冲刷试验，研究了坡面薄层水流的水力学参数特征及产沙变化，结果表明，粒径的雷诺数和弗汝得数都随放水流量而增大，但其流型和流态仍保持不变。径流流速，产沙率均随着流量的增大而呈幂函数增大，阻力系数则随着雷诺数的增大呈幂函数减小。分析薄层水流下理想坡面土壤颗粒的受力情况得出坡面产沙与径流剪切力关系的概念模型。结合试验数据，确定出模型参数的值，并得出试验土壤的临界切应力。 相似文献
6.
Extensive hydroelectric development in the Columbia River system has eliminated most mainstem riverine habitat available for spawning by fall chinook salmon (Oncorhynchus tshawytscha). The two remaining populations, Hanford Reach, Columbia River and Hells Canyon Reach, Snake River, are separated geographically and their status is markedly different. Annual escapements to Hanford Reach have averaged approximately 80 000 adults, while the Snake River run size has declined to <1500 adults over the past 10 years. We compared their spawning habitat characteristics over a range of measurement scales, as a means to identify strategies for rebuilding the weak Snake River population. Physical habitat characteristics of redds were similar for both study areas. Redd locations were correlated with channel characteristics, such as braiding and sinuosity. Several differences between the two spawning areas were identified at the watershed scale: the Hells Canyon Reach had a much steeper longitudinal gradient, was largely confined by bedrock, and had a more variable flow regime. These features are controlling variables that operate at the reach‐scale to limit the availability and size of substrate and other conditions that influence egg deposition and incubation survival. Geomorphological characteristics of the two study sites are sufficiently different to indicate that the production potential of the Hells Canyon Reach population is markedly lower than that of the Hanford Reach population. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
7.
确定泥沙运动有效切应力方法的探讨 总被引：5，自引：1，他引：4
本文通过理论分析及实测资料检验表明,无论对于何种泥沙运动状态,决定泥沙运动的有效切应力既不是沙粒切应力又不是全部切应力,而是介于两者之间,近似为沙粒切应力与全部切应力的几何平均值。这一有效切应力不但是对切应力类水流强度指标的总结,还可以概括平均流速和水流功率等水流强度指标。 相似文献
8.
Peter M. Kiffney George R. Pess Joseph H. Anderson P. Faulds K. Burton Stephen C. Riley 《河流研究与利用》2009,25(4):438-452
Migration barriers are a major reason for species loss and population decline of freshwater organisms. Significant efforts have been made to remove or provide passage around these barriers; however, our understanding of the ecological effects of these efforts is minimal. Installation of a fish passage facility at the Landsburg Dam, WA, USA provided migratory fish access to habitat from which they had been excluded for over 100 years. Relying on voluntary recruitment, we examined the effectiveness of this facility in restoring coho (Oncorhynchus kisutch) salmon populations above the diversion, and whether reintroduction of native anadromous species affected the distribution and abundance of resident trout (O. mykiss and O. clarki). Before the ladder, late summer total salmonid (trout only) density increased with distance from the dam. This pattern was reversed after the ladder was opened, as total salmonid density (salmon + trout) approximately doubled in the three reaches closest to the dam. These changes were primarily due to the addition of coho, but small trout density also increased in lower reaches and decreased in upper reaches. A nearby source population, dispersal by adults and juveniles, low density of resident trout and high quality habitat above the barrier likely promoted rapid colonization of targeted species. Our results suggest that barrier removal creates an opportunity for migratory species to re‐establish populations leading to range expansion and potentially to increased population size. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
9.
卵石推移质运动规律研究对山区河流开发利用意义重大。推移质颗粒一般是以滚动(间或滑动)、跃移等形式运动的。在低水流强度范围内,颗粒运动形式以滚动为主;即使占推移质大部分的跃移颗粒,通常也并不是在起动之后随即跃起,而往往需要先滚动一段距离。因此,有必要进行泥沙颗粒滚动机理研究。本文建立了粗颗粒泥沙滚动力学模型,将滚动步划分为接触步和自由步,经计算得到脱离角、单步运动步长、平均滚动速度等表达式;并采用爱因斯坦方法,修正了其公式中的单步步长和冲刷率,进而得到相应的推移质输沙率公式,并用实际输沙率资料进行了验证。 相似文献
10.
11.
K. L. Sellheim C. B. Watry B. Rook S. C. Zeug J. Hannon J. Zimmerman K. Dove J. E. Merz 《河流研究与利用》2016,32(4):610-621
Gravel augmentation is used in sediment‐starved streams to improve salmonid spawning habitat. As gravel is added to river channels, water surface elevations may rise in adjacent areas, activating floodplain habitat at lower flows, and floodplains inundate more frequently, potentially affecting the quantity and quality of juvenile salmonid rearing habitat. We analysed 5 years of juvenile Chinook salmon Oncorhynchus tschawytscha and steelhead Oncorhynchus mykiss data from snorkel surveys before and after gravel augmentation in the Lower American River, a low‐gradient, highly regulated alluvial river in California's Central Valley. We measured the quality and quantity of rearing habitat (current velocity and areal extent of inundated riparian vegetation) following gravel placement and tested whether these factors affected juvenile abundance. Gravel augmentation increased floodplain extent by 3.7–19.8%, decreased average flow velocity from 1.6 to 0.3 m s?1 and increased the amount of vegetative cover from 0.3% to 22.6%. Juvenile abundances increased significantly for both species following augmentation. However, the strength of the relationship between abundance and habitat variables was greater for smaller salmonids. These results suggest that, in addition to enhancing salmonid spawning habitat, gravel augmentation can improve rearing habitat where channel incision and/or regulated hydrographs disconnect floodplains from main river channels. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
12.
Francisco J. M. SIM?ES 《水科学与水工程》2014,7(2):183-193
The prediction of incipient motion has had great importance to the theory of sediment transport. The most commonly used methods are based on the concept of critical shear stress and employ an approach similar, or identical, to the Shields diagram. An alternative method that uses the movability number, defined as the ratio of the shear velocity to the particle＇s settling velocity, was employed in this study. A large amount of experimental data were used to develop an empirical incipient motion criterion based on the movability number. It is shown that this approach can provide a simple and accurate method of computing the threshold condition for sediment motion. 相似文献
13.
Beyond assessing passage efficiency of fishway structures, there is a need to examine the sublethal impacts of passage on the physiological condition of fish. Muscle and plasma samples were collected from pink salmon (Oncorhynchus gorbuscha) at four sites along a fishway and were compared in order to assess the effectiveness of these methods as they apply to fishway studies. Both plasma and muscle tissue revealed changes consistent with anaerobic activity when fish sampled from within the fishway were compared with field baseline estimates taken from fish sampled 50 m downstream of the fishway entrance. Plasma Cl?, osmolality and haematocrit increased significantly (all p < 0.01) during ascent, whereas muscle glycogen and phosphocreatine declined (both p < 0.03). Both plasma and muscle tissue collected from fish sampled at a site just upstream of the fishway showed physiological profiles that were consistent with metabolic recovery relative to physiological conditions during passage: plasma lactate, haematocrit and muscle lactate had decreased (all p < 0.01), and muscle phosphocreatine increased (p = 0.01). When examining the physiological changes that specifically occurred between the two sites within the fishway structure, we found no differences in plasma samples, but muscle lactate and water content both showed significant changes (both p < 0.05). These results are consistent with the greater sensitivity of muscle tissue than of blood to exercise‐related physiological changes and highlight the usefulness of sampling muscle tissue for assessing fishways that ascended in a short time. Fishway studies could benefit from greater inclusion of physiological tools and approaches to identify the costs of passage and areas of difficulty within a fishway. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
14.
弯曲河道推移质输沙带的研究 总被引：4，自引：0，他引：4
本文建立了适用于弯曲程度不同时的河道泥沙起动流速公式，对环流非充分发展的，床面达到动平衡状态的弯曲河道推移质强烈输沙带进行了研究。导出了弯曲河道内呆烈输沙带的曲线方程，经模型连续弯道内实测输沙带的位置和计算强烈输沙带曲线的比较，结果令人满意。 相似文献
15.
对1950年以来长江中游泥沙输移资料作了初步分析。分析结果表明：20世纪60年代下荆江裁弯后,三口(松滋口、太平口、藕池口)分流分沙减少,下荆江径流量和输沙量相应增加,洞庭湖泥沙淤积减少;80年代中期以后,长江中游干流及洞庭湖出口的年输沙量呈减少趋势,城陵矶至武汉河段河床由淤积转为趋向冲淤平衡三峡工程初期蓄水运用后,长江中游含沙量沿程恢复距离较长,但床沙质部分恢复距离相对较短。 相似文献
16.
Nicole L. Hill Jessamine R. Trueman Ashlee D. Prévost Dylan J. Fraser William R. Ardren James W.A. Grant 《Journal of Great Lakes research》2019,45(2):394-399
By impeding migration and degrading habitat downstream, dam construction has caused population declines in many migratory fish populations. As part of the landlocked Atlantic salmon (Salmo salar) restoration program in Lake Champlain, the Willsboro Dam was removed from the Boquet River, NY in 2015 providing an opportunity to study the effects of dam removal on spawning habitat quality and availability. Spawning habitat surveys were conducted downstream of the dam site in 2014, 2016 and 2017, and in historical spawning grounds upstream in 2016 and 2017. The habitat used was characterized by measuring depth, water velocity, and substrate size at each redd. Mean habitat use did not differ between upstream and downstream sites for any variables in 2016 and only differed for depth in 2017. However, the variance in depth and substrate used for spawning were lower at the upstream site in 2016, likely due to an abundance of habitat. In the downstream site, the mean and variance in depth at redds decreased after dam removal as did the variance in substrate size, increasing the habitat suitability of redds. When compared to literature data, habitat used upstream of the former dam was of medium quality in both 2016 and 2017, and improved downstream from low to medium quality in both column velocity and substrate size after dam removal. This study illustrates that positive shifts in the quality of habitat used can occur rapidly following dam removal by allowing access to suitable spawning habitat upstream and improving habitat downstream. 相似文献
17.
This study investigated the effects of culvert replacement design on fish habitat and fish weight by comparing substrate diversity and weight at three stream simulation (SS)‐design and three bankfull and backwater (BB)‐design sites on the Chequamegon‐Nicolet National Forest, Wisconsin. Stream channel cross‐sections, Wolman substrate particle counts, and single‐pass backpack electro‐fishing survey data were used to quantify fish habitat and fish weight in 50‐m upstream and downstream sample reaches at each site. We applied generalized linear mixed models to test the hypothesis that substrate size and fish weight did not differ according to stream‐crossing design type (SS or BB) and location (upstream or downstream). Substrate particle sizes were significantly greater upstream of the stream crossing when compared to downstream of the stream crossing at both SS and BB sites for riffles and pools. Substrate particle sizes were also significantly greater upstream of BB sites when compared to upstream of SS sites. Results of this study indicated statistically greater individual fish weights upstream of SS‐design sites in comparison to upstream of BB‐design sites in first‐ to third‐order low gradient streams. These results suggested that the SS‐design approach appears to be more effective at transporting sediment downstream, and illustrated the value of using fish weight as an indicator of biological success for stream‐crossing designs. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
18.
浑水推移质分组输沙研究 总被引：4，自引：0，他引：4
天然河流的泥沙输移大多在浑水条件下进行,浑水条件与清水条件下的输沙机理存在一定差异。基于近底泥沙交换三状态随机-力学模式,考虑了床沙与推移质向悬移质的净交换,引入扬动概率,建立了浑水中非均匀推移质分级输沙率公式,进而导出总输沙率及推移质级配的计算式。浑水条件下进行的推移质输移水槽试验和野外实测资料验证了该理论公式的合理性与可靠性,并发现浑水条件下推移质级配可能粗于原始床沙级配。研究结果表明:在浑水中,以悬移质形式存在的砂质泥沙含量对有效估算推移质输沙率有着不容忽视的影响。在某粒级运动泥沙总量不变的前提下,由于一部分沙粒悬浮于水体中,将使得推移质数量相对减少。 相似文献
19.
Bedload transport in alluvial channels has been extensively studied and different equations based on field and/or experimental data have been proposed.Prediction of bed-load transport rate using different equations results in wide ranges which are not always reliable.In this study,some of the universal bedload predictors were evaluated with measured load by a Helley-Smith sampler in the Node River,a gravel bed river in the northeast part of Iran.From 19 sets of data,14 series of data were used to evaluate the bed-load transport equations.The results show that the equations presented by Van Rijn,Meyer-Peter and Mueller,and Ackers and White may adequately predict bedload transport in the range of field data. 相似文献
20.
Reservoir releases on large regulated rivers are increasingly being used to rejuvenate riverine habitat downstream of dams. Determining the effective flow level is complicated by the trade‐off between mobilizing bed particles and retaining coarse sediment in rivers with low sediment supply. This study determined mobilization and transport distance of bed particles using motion‐sensing radio transmitting particles that approximated the reach‐average D84 grain size. The distribution of shear stress at initial motion varied substantially between flood events, and suggests that the sequence of flood events and the history of under‐threshold flows may be an important determinant of bed strength and thus particle mobility. In addition, particle activity was greatest on the rising limb of each flood and was maximized at near bankfull flow. Travel distances did not vary between floods when scaled by transport event duration, and a negative exponential distribution was a good fit to the data. Results of this study provide important insight into individual particle movement, which can be used to inform flow releases and understand the effects of flood magnitude on particle mobility and transport. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献