Hydraulic modelling of fish habitat in urban rivers during high flows     

D. J. Booker 《水文研究》2003,17(3):577-599

In urban rivers, flow regime and channel morphology are the drivers of physical habitat quality for aquatic species. Peak discharges are increased at high flows as a result of impermeable catchments and channel engineering for flood protection schemes. Hazardous conditions and flashy hydrographs mean that measurement of velocities at high flows is a difficult task. This research uses a three‐dimensional computational fluid dynamics (3D‐CFD) model to simulate hydraulic patterns in two urban river channels. A 3D‐CFD code, called SSIIM, was used to simulate hydraulic conditions in two engineered river reaches of the River Tame, Birmingham, UK. These two sites represent channels with different levels of engineering. Models were calibrated and tested using field measurements. Results show that modelled water surface levels and velocity profiles are well simulated. Calibrated roughness heights are compared with those derived from field measurement of sediment size. Numerical experiments are used to assess the relationship between grid resolution in the vertical dimension and the form of the modelled velocity profiles. Biologists have used laboratory experiments to determine maximum sustainable swimming speeds (MSSS) of fish, often in order to assess what level of a particular pollutant may be tolerable. In this work, simulations of high‐flow hydraulic patterns are used to compare velocity patterns with fish MSSS. Results show that when the water levels rise to fill the first channel of the two‐stage channels at the sites, which occurred 16 times in 2000, MSSS are surpassed in the majority of available habitat, suggesting that excessive velocities at high flows are one factor that limits fish habitat. A comparison between the two reaches shows that there is less available habitat in the more modified reach. Conclusions suggest that an approach that integrates water quality issues and physical channel characteristics must be taken in river rehabilitation schemes, as improvements to water quality alone may not be sufficient to improve habitat quality to the desired level. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Bed forms and bend-arc spacings of some coarse-bedload channels in Upland Britain     

J. A. Milne 《地球表面变化过程与地形》1982,7(3):227-240

Seventy-eight riffle to riffle and 80 bend spacings along eleven coarse-bedload, low sinuosity stream channels in upland Britain have been surveyed. Frequency distributions of these spacings are notably right-skewed. The most common repeating distances between riffles and bend inflections are between 4 and 6 channel widths although spacings up to 20 widths are also present. Riffle and pool locations around bends at different stages of planform development indicate that change is largely through increased sinuosity between two consecutive riffles of an original straight reach. Observed straight segments exhibit alternating riffles and pools evenly spaced at 4-6 widths, and most bends have similarly spaced riffles at their inflections in plan, with the intermediate pool at their apex. However angular deflections between axial lines joining inflections indicate existing sequences of bends did not develop from a single straight reach. Bends which are significantly longer than 4-6 widths are of low sinuosity and represent variability in naturally irregular planforms rather than arcs in advanced stages of meander growth. Adjusted bed topography around such long bends takes two forms. Either a single riffle-pool cycle is present with one or both bed forms being longer than average, or a 4-6 widths spacing is maintained by more than one riffle-pool sequence. Locally, the cross-section characteristics of riffles and pools are also influenced by planform location.  相似文献   

A model of two-phase bedload transport in an oregon coast range stream     

W. L. Jackson  R. L. Beschta 《地球表面变化过程与地形》1982,7(6):517-527

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SENSITIVITY ANALYSIS OF HYDRAULIC GEOMETRY     

CAO Shuyou  This research was supported financially by the Foundation for Scholars Return from Abroad of State Educational Committee  the National Natural Science Foundation of China 《国际泥沙研究》1997,(3)

I.INTRODUCTIONThehydraulicgeometryofstablenaturalriversisdeterminedbyceftaincontrolfactors.suchassizeandgradationofboundarymaterial-sorting,transportandarmoring.planformofchannel.ballkstability.amongstothers.Ageometricmodelfornonuniformboundarymaterialhasbeenproposed(Cao,1996).Theentropy-basedthresholdbankprofiletheory(CaoandKnight,1996).thenext'solutionofthestablechannelparadox,basedonShionoandKnight's(1991)solutionofthedepthmean-averagedmomentumequationatthejunctionpointsareemployedto…  相似文献   

河口涨潮槽的演变及治理   总被引：16，自引：0，他引：16  

沈焕庭  李九发  金元欢 《海洋与湖沼》1995,26(1):83-89

根据长江口１９５８－１９８７年的地形、水文测量资料和研究成果，对河口涨潮槽的形态特征、水文泥沙特性、形成原因与演变规律作较系统的分析研究。结果表明，涨潮槽呈上口窄下口宽的喇叭形，延伸方向受口外潮波传播方向制约，潮波更多地呈现驻波性质；涨潮流起主导作用，余流方向指向上游，涨潮期含沙量大于落潮期；涨潮槽的水文泥沙特性有明显的大小潮，洪枯季和年际变化，其分布可从口外海滨－直延伸到潮流界；按成因涨潮槽可分  相似文献   

双通道声学水位计     

孙强 《海洋技术学报》2002,21(1):53-56

双通道声学水位计是在 SSA1- 1型声学水位计的基础上 ,通过一台主机带两个探头 ,进行准同步测量而实现的  相似文献   

Numerical modelling of shoal pattern formation in well-mixed elongated estuaries   总被引：1，自引：0，他引：1  

A. Hibma  H. J. de Vriend  M. J. F. Stive 《Estuarine, Coastal and Shelf Science》2003,57(5-6):981-991

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20年来珠江口伶仃洋滩槽变化及演变分析   总被引：10，自引：1，他引：10  

陈水森  黎夏  邹春洋  祝功武 《海洋科学》2001,25(6):52-54

珠江源远流长,流域广大 ,它是西江、北江和东江的总称。全长２２１４ｋｍ的西江 ,发源于云南省曲靖市马雄山,经珠海市磨刀门流入南海 ,是中国第三大河 ,也是珠江的主要排洪干道。珠江口伶仃洋主要接受来自西江、北江和东江的河水,主要是其四大口门虎门、蕉门、洪奇门、横门来水 ,它们总共占了珠江总径流量的５３．４%。但仅就西、北江而言 ,则有６２．１%的洪峰径流经由这四大口门流入伶仃洋 ,分别占珠江总径流量的１８．５ % ,１７．３% ,６．４ % ,１１．２%［［１１］］。。另另外外 ,,在在八八大大分分流流水水道道中中 ,,泄泄出出径径…  相似文献   

江苏辐射沙洲水道垂线平均余流的计算与分析   总被引：3，自引：0，他引：3       下载免费PDF全文

吴德安  张忍顺  沈永明 《海洋与湖沼》2007,38(4):289-295

根据辐射沙洲邻近主水道和中心沙洲滩面水道33个站次的准同步实测潮流资料, 计算了各站位垂线平均欧拉余流、斯托克斯余流、拉格朗日余流, 并分别进行了逐站位的分析和比较.各站位斯托克斯余流相对较小, 在水道口门处斯托克斯余流较大, 余流流向大都沿涨潮流向, 豆腐渣腰门水道及其以东站位的斯托克斯余流则大致沿落潮流向.欧拉余流和拉格朗日余流大小和流向基本一致.研究海域存在着半封闭的顺时针方向的海水净输移.西洋水道和条鱼港水道是辐射沙洲中心腹地的净进水通道, 而豆腐渣腰门水道、陈家坞槽水道、外王家槽水道、苦水洋海域水道则是净出水通道.  相似文献   

Evidence of across-shelf transport of fine-grained sediments: turbidite-filled shelf channels in the Campanian Aberdeen Member, Book Cliffs, Utah, USA   总被引：2，自引：0，他引：2  

SIMON A. J. PATTISON  R. BRUCE AINSWORTH†  TREVOR A. HOFFMAN‡ 《Sedimentology》2007,54(5):1033-1064

The shore‐normal transport of fine‐grained sediments by shelf turbidity currents has been the focus of intense debate over the last 20 years. Many have argued that turbidity currents are unlikely to be a major depositional agent on the shelf. However, sedimentological, architectural, stratigraphic and palaeogeographic data from the Campanian Aberdeen Member, Book Cliffs, eastern Utah suggests otherwise and clearly demonstrates that storm‐generated and river flood‐generated underflows can transport a significant volume of fine‐grained sediments across the shelf. These across‐shelf flowing turbidity currents cut large subaqueous channel complexes up to 7 m deep, tens of kilometres basinward of their time‐equivalent shoreface. The shelf channels were filled with organic‐rich siltstones, mudstones and very fine‐ to fine‐grained Bouma‐like sandstone beds, including wave‐modified turbidites, hyperpycnites and classical turbidites. Deposition was above storm wave base. Palaeocurrent data reveal an overwhelmingly dominant across‐shelf (east–south‐east), offshore‐directed transport trend. Tectonic activity and/or concomitant palaeogeographic reorganization of the basin may favour the generation of these turbidite‐rich shelf deposits by altering the relative balance of wave versus fluvial energy. Increased erosion and sediment supply rates, because of tectonic uplift of the hinterland, may have increased the probability of fluvial dominance along the coastline and, hence, the possibility of submarine channelization in front of the river mouths. Additionally, the coastline may have become more sheltered from direct wave energy, thus allowing the fluvial processes to dominate. Seasonal increases in rainfall and storm activity may also favour the generation of across‐shelf underflows. On wave‐dominated shorelines, isolated shelf channels and lobes are most likely to be found down‐dip of fluvial‐feeder systems in relatively high sediment supply settings. These features are also most likely to occur in systems tracts that straddle a sequence boundary, especially those which are tectonically generated, as these would enhance the potential for altering basin morphology and, hence, the balance of fluvial and wave energy. Isolated shelf channels are recognized in older and younger strata in the Book Cliffs region, implying that wave‐supported gravity flows were a recurrent phenomena in the Campanian of Utah. It is probable that isolated shelf bodies are preserved in other stratigraphic intervals in the Cretaceous Western Interior of North America, and other basins worldwide, and are currently being overlooked or misidentified. Shoreface‐to‐shelf facies models should be revised to incorporate turbidite‐rich shelf deposits in some shelf settings.  相似文献