Combining remote sensing with physical flow laws to estimate river channel geometry

A reliable representation of river terrains is essential to river research. Field surveys of river channel geometry are time‐consuming, costly, and logistically constrained and thus would encounter difficulties to achieve sufficient spatial coverage, resolution, and frequency of resurvey. This paper aims to demonstrate an efficient approach to building a river terrain model (RTM), the emphasis being on how to combine bathymetry and topography derived from satellite images captured at different flow stages. A method for calculating the difference between high and low stages (DHLS) based on the uniform‐flow theory is proposed. Calculations are carried out for a 13‐km long meandering section of the gravel‐bed Goulais River in Canada, which features pools and riffles, alternating point bars, and midchannel bars. A RTM for this complex section has been successfully produced. It consists of three data components: bathymetry at low stage, topography at high stage, and DHLS. The results capture realistic characteristics, including thalweg shift, steep outer banks, and gradual inner banks. They also show realistic longitudinal and lateral locations of pools and riffles. To illustrate potential applications of RTM, this paper has computed extreme bed shear stresses at bankfull discharge through hydrodynamics simulations of depth‐averaged flow in the river section and further estimated bed‐sediment grain‐size distributions. The estimates compare well with field measurements. The DHLS can vary significantly along a river channel. The proposed method for determining it is not site‐specific, and hence applicable to other rivers. The novelty of the methodology discussed lies in combining remote sensing techniques with physical flow laws.     

The value of a desk study for building a national river obstacle inventory

This study evaluates two desk‐based approaches for building an inventory of man‐made river obstacles. The creation of a river obstacle inventory is a vital first step in developing a prioritization process for obstacle removal and/or modification. In this study, a desktop geographical information system analysis of two rivers and their tributary network was undertaken, using two different approaches. The first involved analysing historical maps, satellite imagery, and Ordnance Survey Ireland Discovery Series maps and producing a geo‐referenced layer of all the potential river obstacles. The second involved developing a geo‐referenced layer of potential river obstacles based on the intersections between elements of the transport network (roads and railways) and river systems. To determine the effectiveness of the desk studies, the located obstacles were cross‐referenced with actual obstacles verified through a field survey. The desk studies identified several thousand potential obstacles. The study utilizing a range of maps consistently located a greater number of actual obstacles than the desk study based on intersections between the transport and river networks. The results indicate that desk‐based research offers an efficient and effective method for locating river obstacles and can guide subsequent field surveys aimed at confirming the presence of obstacles. This is particularly useful for eliminating from study large stretches of rivers that would otherwise need to be walked to confirm the presence, or otherwise, of potential river obstacles. In this regard, desk‐based exercises can offer opportunities to save on both time and cost in larger river assessments.     

Response of a barrier estuary to climate change and river regulation using attractor analysis: Snowy River estuary,Australia

The evolution of the entrance channel of the Snowy River estuary in response to river regulation and climate change is predicted. The predictions are made in terms of the physical attractors that define possible long‐term states of the estuary entrance condition. The classification of these attractors shows the dependence of the entrance stability on the catchment inflows and the present entrance depth. The Snowy River estuary in south‐eastern Australia is a barrier estuary with an unstable entrance that tends to closure. The classification from the attractor map shows that the estuary entrance has changed from predominantly stable to a predominantly unstable state attributable to diversion of water from the upper catchment. The introduction of a series of environmental flow regimes, commencing in 2002, has returned 8% rising to 21% of the mean annual natural flow, but this study shows that the releases provide limited improvement in entrance stability. Additionally, the predicted effects of climate change for this region include increased mean sea level (MSL), decreased annual rainfall, and increased incidence of storms. These changes will decrease stability, primarily through the rise in MSL. The rise in sea level will increase the plan area of the tidal basin, increasing the tidal prism, and hence drawing in more marine sand. The application to the Snowy River estuary provides a proof of concept of the attractor classification to support estuary management.     

Lake Chivero (Zimbabwe) and its climatic environment

The mean temperatures and mean maximum temperatures in Lake Chivero indicate a warming trend, which is not evident in mean minimum temperatures. The mean annual precipitation also exhibits a declining trend, as does the Manyame River flow trend. The relation between run‐off, river flow and precipitation indicate a discontinuous trend at a piecewise regression breakpoint of 998 mm precipitation. Above the breakpoint, the river flow is related exponentially with precipitation, while the run‐off relationship is linear, although with a low R² value. Below the breakpoint, both the run‐off and river flow exhibit a low variance accountability. Considered within the context of the IPCC findings of a subcontinent warming faster than the rest of the southern hemisphere, along with declining precipitation, these data suggest an uncertain water supply security for the City of Harare and its satellite settlements. The detectable warming of the lake, taken together with observations in Lake Kariba, also suggests an ecological shift that could be dominated by a shift to a permanent cyanobacteria‐dominated ecosystem, which is currently dominated by Microcystis and Anabaena species.     

固定化硝化细菌与聚磷菌对南昌市内河流水污染物降解的研究

针对南昌市主要内河流的污染问题,结合南昌市主要内河流抚河故道和玉带河的水质现状特点,筛选出了优势硝化细菌和聚磷菌,并研究优势菌种对南昌市内河流中氨氮、总磷的固定化降解效果。结果表明:硝化菌XH3对亚硝酸盐氮的降解率最高达到100%,硝化菌YH3对氨氮的降解率为82.75%,聚磷菌JP2对总磷的降解率为58.57%;优势菌株XH3、YH3、JP2按照质量比1∶1∶1的比例进行配比,发现三者配比的混合菌对氨氮、总磷的降解率达85%、22.86%;通过采用PVA+添加剂制备了含优势菌种的固定化载体,利用该载体研究在曝气24 h条件下对南昌内河流中氨氮、总磷的降解效果,研究表明该载体对模拟南昌市内河流中氨氮、总磷的降解效果分别能达到82.70%、79.27%。综合分析得出,该方法为南昌市内河流的整治提供了一个可行的有效途径。     

内蒙古高原典型草原内陆河流域径流的时序演变特征

高原内陆河在我国半干旱地区社会经济发展的区域水资源开发利用过程中起到了重要的支撑作用,认识其演变特征及进行模拟对于流域的可持续发展具有重要的意义。以内蒙古高原典型草原内陆河流域——巴拉格尔河流域为研究对象,基于1959-2015年的水文、气象和社会经济等数据,采用双累积曲线法、累积距平法、改进的M-K趋势检验法和小波变换法对流域径流序列的变化特征进行了解析,并通过细化降水特征因素影响和以社会经济指标量化人类活动影响,运用统计相关检验法筛选径流时序演变模拟的主要输入要素,以改进的BP神经网络实现了水文年、季尺度下径流的时序演变模拟。结果表明:巴拉格尔河流域径流量在年、季尺度下呈现显著减少趋势;径流变化的突变年份为1998年,在这之前受到气候变化为主的影响,而在这之后为加入人类活动的双重影响;年、枯水季径流序列均存在6a和30a周期,而丰水季径流在分析序列内无明显周期变化;降水指标中的降水量、降水天数和降水次数,气候因素中的蒸发和相对湿度,以及人类活动的所有指标是与径流显著相关的影响因素;在无法实现分布式水文模拟时,改进的BP神经网络可以较好地模拟该流域径流的时序演变过程。     

基于一维水动力模型的洪水顶托影响分析

干支流洪水遭遇易发生顶托现象,导致河道行洪不畅,极大增加了河道防洪风险。以第二松花江(简称二松)洪水对嫩江洪水的顶托作用为工程背景,采用一维水动力学方法模拟计算不同洪水组合下嫩江受二松洪水顶托情况,并基于模型模拟结果进一步量化分析嫩江受顶托距离、顶托程度等。结果表明:嫩江受二松洪水顶托距离情况较为复杂,与两江洪水的相对大小密切相关,两江洪水量级相当时,顶托距离为距三岔河口32km左右;二松洪水相对越大,受顶托距离越远且顶托程度越大;在嫩江10年一遇、二松50年一遇洪水组合下,嫩江受顶托最远到达距三岔河口55km处,顶托影响高度达2.14m。     

基于多源数据的黑河流域日尺度蒸散发量模拟

植被蒸散发是地表水量平衡和热量平衡的重要参量,也是衡量植被生长状况和作物产量的重要指标,同时也是进行流域水资源优化配置的依据。遥感技术的快速发展使其成为区域尺度蒸散发模拟的重要手段。以黑河流域为例,构建遥感驱动的蒸散发模拟模型,结合多源遥感数据(MODIS、TRMM等)以及GLDAS全球陆面数据同化系统数据,对黑河流域2005、2010、2015年三个时期的潜在蒸散发和实际蒸散发进行了时间尺度为每日、空间尺度为1km的模拟。研究结果表明:潜在蒸散发月际变化明显,从5月开始增长,于7月达到峰值,然后逐渐减少;实际蒸散发在月份之间变化趋势明显,在2015年均达到了最高值;精度检验结果表明本研究采用的两个模型均达到了很好的效果,Kristensen-Jensen模型更适合用于黑河流域。本研究为黑河流域地表特征数据集提供了重要的日尺度蒸散发数据。     

利用侧扫声呐实现船舶目标的快速识别

根据回波探测原理,研究了一种利用声呐对内河航运船舶进行监测的方法。利用项目组在广西西江航道上建立的一套侧扫声呐船舶吃水深度检测系统,获取了大量的监测数据。通过对这些数据的分析,研究了船舶目标和鱼群、渔网、垃圾漂浮物等伪目标之间的区别,总结出船舶目标的能量变化特征和线型结构特征。根据这些特征,提出了一种针对船舶目标的快速识别方法。最后通过试验,证明该方法具有检测率高、虚警概率小、实时性好等优势,为进一步实现内河航运船舶航行状态的智能监测提供了一种技术手段。     

雅砻江流域产沙区及人类活动影响分析

本文根据雅砻江干流主要控制站泥沙和径流资料分析得出：泸宁～小得石区段为该流域重点产沙区;并且１９８２年后,由于人类活动影响,使该流域泥沙以３４．４％的速度增加,应引起有关部门重视,并采取有效治理措施。