共查询到20条相似文献，搜索用时 0 毫秒
1.
下荆江尾闾的熊家洲河段自1950年斜槽裁弯形成新生汊道分流,使得下游七弓岭弯道水动力发生调整,进而加剧河道崩岸,影响河势稳定。采用水文资料和地形数据,基于MIKE21软件建立熊家洲弯道上下游河段(监利—螺山)的二维水动力数值模型,设置不同来流量和新汊道尺寸,模拟新汊道条件改变对七弓岭弯道水动力调整的影响。研究表明:汊道展宽至分流明显后,主流水动力轴线沿七弓岭弯道的凸岸偏转;当汊道尺寸较大时,汊道出流近似垂直于七弓岭弯道颈口上游河岸,加剧颈口上游未守护河段的崩岸,这为原型观测所证实。 相似文献
2.
Many of the Upper Missouri River dikes have been notched to create additional shallow water habitat (SWH, operationally defined as areas in the stream with depth < 1.5 m, and velocity < 0.75 m s?1) for fish populations. The goal of this study was to quantify the additional SWH gained from notching these dikes and to evaluate their performance under different flow conditions. A coupled field and numerical study was performed on a reach of the Missouri River, near Nebraska City, NE, which contains a number of dikes notched in 2004. The numerical simulations showed that the SWH criterion for depth was more difficult to satisfy in the study reach than the SWH criterion for velocity. Notching the dikes resulted in a slight shift of the bankline due to local erosion in the vicinity of the dikes and the formation of scour holes downstream of the notches. Results from the study suggested that notching the dikes had limited impact on the SWH because the area gained from the bankline shift was offset by the area lost from the scour holes formation. The performance of the notched dikes in sustaining the minimum habitat suitability conditions for the Missouri River ecosystem was also investigated. These conditions corresponded to discharges < 709 m3 s?1 for the period from mid‐July to mid‐August, or equivalently SWH areas > 5225 m2 dike?1 during the same period. Analysis of the Missouri River annual discharge records at the study site showed that the dikes can provide the minimum required SWH for mean annual discharges < 667 m3 s?1. For mean annual discharges > 667 m3 s?1, new alternative structures or restoration facilities were needed, in addition to the existing dikes, to sustain the minimum required SWH. The dikes were not effective in providing any SWH for mean annual discharges > 2000 m3 s?1. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
Decisions on managed flow releases in regulated rivers should be informed by the best available science. To do this, resource managers require adequate information regarding the tradeoffs between alternative methodologies. In this study, we quantitatively compare two competing multivariate habitat models for juvenile Chinook salmon (Oncorhynchus tschawytscha), a highly valued fish species under serious decline in a large extent of its range. We conducted large‐scale snorkel surveys in the American River, California, to obtain a common dataset for model parameterization. We built one habitat model using Akaike Information Criterion analysis and model averaging, ‘model G’, and a second model by using a standard method of aggregating univariate habitat models, ‘model A’. We calculated Cohen's kappa, percent correctly classified, sensitivity, specificity and the area under a receiver operator characteristic to compare the ability of each model to predict juvenile salmon presence and absence. We compared the predicted useable habitat of each model at nine simulated river discharges where usable habitat is equal to the product of a spatial area and the probability of habitat occupancy at that location. Generally, model G maintained greater predictive accuracy with a difference within 10% across the diagnostic statistics. Two key distinctions between models were that model G predicted 17.2% less useable habitat across simulated flows and had 5% fewer false positive classifications than model A. In contrast, model A had a tendency to over predict habitat occupancy and under predict model uncertainty. The largest discrepancy between model predictions occurred at the lowest flows simulated and in the habitats most likely to be occupied by juvenile salmon. This study supports the utility and quantitative framework of Akaike Information Criterion analysis and model averaging in developing habitat models. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
4.
QI Peng HOU Yi-jun Institute of Oceanology Chinese Academy of Sciences Qingdao ChinaWANG Yong-xue State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian China 《水动力学研究与进展(B辑)》2004,16(5)
1 . INTRODUCTIONAccordingtoRef .[1],themotionofashipmooredagainstquayinaharborcanbestudiedintwosteps :harborwaveconditionsandwaveexcit ingforcesactingonthemooredshipshouldbegotfirst,andthendynamicresponsesofthemooringsystemincludingtheshipunderwaveexcitingforcescanbestudiedseparately .Asthefirststep ,ahybridmodelbasedonthecombinationoftheBoussinesq typeshallow waterwavemodelandthe3Dviscousflowmodelisproposedinthispaperforthetime domaincalculationofwaveexcitingforcesonmooredshipsinaharbor… 相似文献
5.
6.
喻海军;范玉燕;曹大岭;陈伟 《人民珠江》2021,42(12)
排水效果评估是海绵城市建设的必要环节,城市雨洪模型则是评估工作的重要支撑工具。以北京市某小区为例,基于一二维耦合的城市雨洪模型构建了研究区域精细化排水模型,模拟分析了海绵化改造方案实施前后小区降雨径流、排水和地表积水等要素的变化情况。结果表明构建的排水模型可以较好地反映小区排水现状,拟定的排水系统海绵化升级改造方案可以有效地改善研究区域的排水情况,管网溢流和地表积水情况明显减少。研究结果可为排水小区管网水力状况数值分析及海绵城市建设与管理提供一定的技术参考。 相似文献
7.
8.
中国中小流域地区洪水灾害频发,探究新型城市雨洪模型是当下的研究热点。通过耦合水文模型与二维水动力模型的方法,使得在模拟城市下垫面洪水淹没情况的同时,又能使模拟达到较快的运算速度。以泉州市梅溪流域为例,探究耦合模型在中国中小流域范围应用的可行性。结果表明,耦合模型模拟水量平衡误差极小,淹没水深结果与验证值吻合较好。根据对淹没水深图与达最大水深时间图的分析,得到区域范围洪水的空间分布及时间分布,可为中小流域洪水治理提供决策支持。但中小流域水文数据匮乏一定程度上限制了模型的可靠性。 相似文献
9.
风场是影响湖泊水动力的重要因素,它可以改变水体运动速度和方向,影响各种物质在湖泊内的输移扩散。通过分析博斯腾湖大湖区风场,准确估算出风力、风向变化情况,构建了博斯腾湖平面二维水动力模型。应用计算模型对博斯腾湖水动力进行模拟预测,分析不同风向、风速对湖泊流场结构的影响,为进一步研究博斯腾湖水动力和污染物输移扩散提供理论依据。 相似文献
10.
向家坝水电站以发电为主,但其运行受引航道通航安全水流流态的限制。根据华东电网典型日负荷统计特性,考虑到机组运行特性以及水位小时变幅与日变幅条件的要求,按照实际水流条件拟定5种向家坝水电站日发电调节流量。采用二维水动力模型揭示电站在不同发电流量运行时下游引航道口门区的流态,使用MIKE21对模型求解,从航道的横向流速、纵向流速、水位变幅以及回流情况等指标选择出两种可行的调度工况。最后,通过比较两种工况的日发电量,选择出最适合向家坝水电站的调度模式。按此模式调度,向家坝水电站的平均出力为2 914 MW,日发电量为7 285×104 kW·h。 相似文献
11.
Both water managers and researchers have the same goal when it comes to fish conservation, namely, to sustain, to improve or to restore aquatic habitat. To this aim, two‐dimensional (2D) hydrodynamic models have been widely used in aquatic habitat studies because they simulate flow with high accuracy and can predict habitat dynamics. The River2D model is able to integrate the habitat suitability curves for fish life stages with the simulated depth and velocity fields and the riverbed characteristics of substrate and cover, thereby estimating the corresponding weighted usable area, and thus predicting the potential distribution of fish species in the river. However, little is known about the in situ variability associated with such predictions both for hydraulic and biological data, whereas ecological responses are known to be driven by variability. Moreover, when calculating habitat availability, differences can be found by considering in the weighted usable area formulation substrate or cover or even both. To test the level of predictive accuracy of hydraulic and biological simulations, we modelled the habitat use by two fish species, the Iberian barbel Luciobarbus bocagei and the Iberian straight‐mouth nase Pseudochondrostoma polylepis, according to their requirements for depth, velocity, substrate and cover and then compared measured and simulated hydraulic and biological outcomes using the River2D model. Results indicate that 2D simulation depends on data collection, especially the density and location of bed topography points. Substantial differences were found in the biological responses. Results may differ when choosing different habitat availability variables. Similarly, habitat use may also be influenced by other biotic and abiotic interactions occurring in ecosystems, and restoration planning should be aware of such variability. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
12.
Three canal control systems (manual upstream control, automatic upstream control and automatic downstream control) were studied for the main canal of the Shoeibieh irrigation project in Iran. The canal and the selected control systems were modelled in a hydrodynamic modelling package. The operational performances of the canal control systems were investigated and quantified for two water delivery schedules, one with small, but frequent adjustments and the other one with big, but infrequent adjustments. Based on the results of the study, automatic upstream control with a small step delivery schedule has been selected for the project.Paper presented at the European Conference Advances in Water Resources Technology, Athens, 20–23 March 1991. 相似文献
13.
Stream restoration was implemented on the Upper Arkansas River near Leadville, Colorado, to improve brown trout (Salmo trutta) populations. Metals pollution and channel disturbance associated with historic mining, land use, and water development degraded aquatic and riparian habitat. Changes in instream habitat quality following restoration were investigated with a before–after–control–impact study design. Baseline, as‐built, and effectiveness surveys were conducted in 2013, 2014, and 2016, respectively. Two‐dimensional hydrodynamic modelling with River2D was used to estimate weighted usable area (WUA) for adult, juvenile, fry, and spawning brown trout across a range of flows. WUA was calculated from habitat suitability curves for velocity, depth, and channel substrate. Foraging positions (FP) and habitat heterogeneity were also evaluated as indices of habitat quality. All results were analysed with analysis of variance. At impact sites, WUA increased by 12.2% from 2013 to 2014 but decreased by 10.2% from 2014 to 2016, whereas FP increased by 24.8% from 2013 to 2014 but decreased by 26.1% from 2014 to 2016. Spawning habitat increased 53.3% from 2014 to 2016 at impact sites. The 15.4% increase in depth variability from 2013 to 2016 indicates that habitat heterogeneity was enhanced at impact sites. No changes in WUA, FP, or habitat heterogeneity were observed at control sites. Although changes in WUA and FP suggest that initial habitat improvements were not sustained, increased spawning habitat and depth heterogeneity suggest otherwise. Our results highlight the value of monitoring strategies that utilize multiple lines of evidence to evaluate restoration effectiveness, inform adaptive management, and improve restoration practices. 相似文献
14.
岩滩水电站扩建工程为地下式厂房,检修排水系统和渗漏排水系统从可研到施工图阶段经过了多次的优化研究工作,最终的设计考虑了经济性、安全性、扩建工程的地下厂房的特性及规范对于防止厂房倒灌被淹的要求。目前全部排水系统已通过验收并运转良好,证明了整个设计优化过程取得了预期的效果。 相似文献
15.
Over the past century, flow regulation and vegetation encroachment have reduced active channel widths along the central Platte River, Nebraska. During the last two decades, an annual program of in‐channel vegetation management has been implemented to stabilize or expand active channel widths. Vegetation management practices are intended to enhance riverine habitats which include nocturnal roosting habitat for sandhill cranes. Evaluating the success of other management treatments such as streamflow modification requires an understanding of how flow shapes the sandbars in the river and how sandbar morphology interacts with flow to create crane habitat. These linkages were investigated along a 1‐km managed river reach by comparing the spatial pattern of riverine roosts and emergent sandbars identified with aerial infrared imagery to variables computed with a two‐dimensional hydraulic model. Nocturnal observations made multiple years showed that the area and patterns of riverine roosts and emergent sandbars and the densities of cranes within roosts changed with stage. Despite sandbar vegetation management, low flows were concentrated into incised channels rather than spread out over broad sandbars. The flow model was used to compute hydraulic variables for identical streamflows through two sandbar morphologies; one following a period of relatively high flow and the other following the low‐flow period. Compared with the simulation using the morphology from the antecedent high flow, the simulation using the morphology from the antecedent low flow produced a smaller quantity of available wetted area. These remote‐sensing observations and hydraulic simulations illustrate the importance of considering flow history when designing streamflows to manage in‐channel habitat for cranes. Published in 2008 by John Wiley & Sons, Ltd. 相似文献
16.
为深入分析淮河干流六坊堤段南、北汊河道及上、下六坊堤行洪区过流能力,基于MIKE 11、21软件分别建立淮河干流峡山口至汤渔湖上口段一维和二维水动力学模型,进行分岔河道行洪和行洪区分洪整体模拟。通过模型模拟计算,确定现状峡山口至上六坊堤段河道的过流能力达不到规划设计要求,上六坊堤行洪区行洪能力达不到淮河洪水调度方案规定的行洪流量,为上、下六坊堤段行洪区调整和建设方案提供了技术支撑。 相似文献
17.
以盘溪梯级水电站的大洋水库为例,采用改进的Tennant法、年内展布法、Q90法、改进的频率法以及NGPRP（northern great plains resource program）法计算大洋水库应下泄的最小生态流量。选取95%保证率为保护目标,通过进一步的合理性分析,分析5种方法在95%保证率下的满足程度,从而提出年内展布法和改进的频率法是最适合该地区的最小生态流量计算方法。在满足95%保证率的情况下,选取年内展布法和改进的频率法的内包线得到大洋水库应下泄的最小生态流量过程,并以此思路推求出盘溪梯级一级电站至四级电站区间最小生态流量过程。 相似文献
18.
二维水力模拟在河流生态需水湿周法中的应用 总被引：1，自引：0，他引：1
湿周法是河流生态需水量计算中使用较为常见的一种水力学方法,通常采用一维的水力分析结果作为计算依据。二维水力模拟能提供更为细致全面的河道水力参数分布,通过对某水电站坝下13.3 km河道进行平面二维水力模拟,对其在湿周法中的应用进行了探讨。采用弗汝德数(Fr)作为浅滩生境划分标准,把浅滩生境较为集中的河段作为湿周法分析的浅滩河段。随后根据平面二维水力模拟结果,给出了浅滩断面相对湿周-流量关系曲线,采用斜率为1的斜率法计算得到了各浅滩断面的生态需水量。结果表明,采用二维水力模拟结果给出的曲线更为合理。 相似文献
19.
C. C. Muhlfeld L. Jones D. Kotter W. J. Miller D. Geise J. Tohtz B. Marotz 《河流研究与利用》2012,28(7):940-959
Hungry Horse Dam on the South Fork Flathead River, Montana, USA, has modified the natural flow regimen for power generation, flood risk management and flow augmentation for anadromous fish recovery in the Columbia River. Concern over the detrimental effects of dam operations on native resident fishes prompted research to quantify the impacts of alternative flow management strategies on threatened bull trout (Salvelinus confluentus) and westslope cutthroat trout (Oncorhynchus clarkii lewisi) habitats. Seasonal and life‐stage specific habitat suitability criteria were combined with a two‐dimensional hydrodynamic habitat model to assess discharge effects on usable habitats. Telemetry data used to construct seasonal habitat suitability curves revealed that subadult (fish that emigrated from natal streams to the river system) bull trout move to shallow, low‐velocity shoreline areas at night, which are most sensitive to flow fluctuations. Habitat time series analyses comparing the natural flow regimen (predam, 1929–1952) with five postdam flow management strategies (1953–2008) show that the natural flow conditions optimize the critical bull trout habitats and that the current strategy best resembles the natural flow conditions of all postdam periods. Late summer flow augmentation for anadromous fish recovery, however, produces higher discharges than predam conditions, which reduces the availability of usable habitat during this critical growing season. Our results suggest that past flow management policies that created sporadic streamflow fluctuations were likely detrimental to resident salmonids and that natural flow management strategies will likely improve the chances of protecting key ecosystem processes and help to maintain and restore threatened bull trout and westslope cutthroat trout populations in the upper Columbia River Basin. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
20.
Han Longxi 《水科学与水工程》2008,1(1):10-17
Simulations of water flow in channel networks require estimated values of roughness for all the individual channel segments that make up a network. When the number of individual channel segments is large, the parameter calibration workload is substantial and a high level of uncertainty in estimated roughness cannot be avoided. In this study, all the individual channel segments are graded according to the factors determining the value of roughness. It is assumed that channel segments with the same grade have the same value of roughness. Based on observed hydrological data, an optimal model for roughness estimation is built. The procedure of solving the optimal problem using the optimal model is described. In a test of its efficacy, this estimation method was applied successfully in the simulation of tidal water flow in a large complicated channel network in the lower reach of the Yangtze River in China. 相似文献