Real-time flood forecasting of Huai River with flood diversion and retarding areas

A combination of the rainfall-runoff module of the Xin’anjiang model, the Muskingum routing method, the water stage simulating hydrologic method, the diffusion wave nonlinear water stage method, and the real-time error correction method is applied to the real-time flood forecasting and regulation of the Huai River with flood diversion and retarding areas. The Xin’anjiang model is used to forecast the flood discharge hydrograph of the upstream and tributary. The flood routing of the main channel and flood diversion areas is based on the Muskingum method. The water stage of the downstream boundary condition is calculated with the water stage simulating hydrologic method and the water stages of each cross section are calculated from downstream to upstream with the diffusion wave nonlinear water stage method. The input flood discharge hydrograph from the main channel to the flood diversion area is estimated with the fixed split ratio of the main channel discharge. The flood flow inside the flood retarding area is calculated as a reservoir with the water balance method. The faded-memory forgetting factor least square of error series is used as the real-time error correction method for forecasting discharge and water stage. As an example, the combined models were applied to flood forecasting and regulation of the upper reaches of the Huai River above Lutaizi during the 2007 flood season. The forecast achieves a high accuracy and the results show that the combined models provide a scientific way of flood forecasting and regulation for a complex watershed with flood diversion and retarding areas.

RF-CLASS： A remote-sensing-based flood crop loss assessment cyber-service system for supporting crop statistics and insurance decision-making

Floods often cause significant crop loss in the United States. Timely and objective information on flood-related crop loss, such as flooded acreage and degree of crop damage, is very important for crop monitoring and risk management in ag- ricultural and disaster-related decision-making at many concerned agencies. Currently concerned agencies mostly rely on field surveys to obtain crop loss information and compensate farmers＇ loss claim. Such methods are expensive, labor intensive, and time consumptive, especially for a large flood that affects a large geographic area. The results from such methods suffer from inaccuracy, subjectiveness, untimeliness, and lack of reproducibility. Recent studies have demonstrated that Earth observation （EO） data could be used in post-flood crop loss assessment for a large geographic area objectively, timely, accurately, and cost effectively. However, there is no operational decision support system, which employs such EO-based data and algorithms for operational flood-related crop decision-making. This paper describes the development of an EO-based flood crop loss assessment cyber-service system, RF-CLASS, for supporting flood-related crop statistics and insurance decision-making. Based on the service-orientated architecture, RF-CLASS has been implemented with open interoperability specifications to facilitate the interoperability with EO data systems, particularly the National Aeronautics and Space Administration （NASA） Earth Observing System Data and Information System （EOSDIS）, for automatically fetching the input data from the data systems. Validated EO algorithms have been implemented as web services in the system to operationally produce a set of flood-related products from EO data, such as flood frequency, flooded acreage, and degree of crop damage, for supporting decision-making in flood statistics and flood crop insurance policy. The system leverages recent advances in the remote sensing-based flood monitoring and assessment, the near-real-time availability of EO data, the service-oriented architecture, geospatial interoperability standards, and the standard-based geospatial web service technology. The prototypical system has automatically generated the flood crop loss products and demonstrated the feasibility of using such products to improve the agricultural decision-making. Evaluation of system by the end-user agencies indicates that significant improvement on flood-related crop decision-making has been achieved with the system.

The impact of earlier flood recession on metacommunity diversity of wintering waterbirds at shallow lakes in the middle and lower Yangtze River floodplain

The hydrological regime in wetlands plays an important role in the process of wintering waterbird metacommunity assemblage.However,increasing frequency of extreme climate and the intensification of human activities,such as the construction of sluices and dams,have resulted in frequently abnormal hydrological regime in the middle and lower Yangtze River floodplain.In recent years,earlier flood recession has become one of the main hydrological problems faced in the shallow lakes,having a great impact on wetland biodiversity.It is necessary to understand the impact of earlier flood recession on waterbirds,an indicator of wetland biodiversity,and the metacommunity concept is helpful to elucidate the underlying mechanism involved in the processes of assemblage by waterbird communities.In this study,we surveyed the wintering waterbirds at three sub-lakes of Caizi Lakes during 2019-2020 and 2020-2021 and compared the richness,abundance,alpha and beta diversity of waterbirds in and among local metacommunities under earlier flood recession and normal hydrological regime.The results showed that the earlier flood recession reduced the species richness in the early stage and abundance in the late stage,it also reduced the Shannon-Wiener index in the early stage and increased the dissimilarity between and within waterbird metacommunities in the late stage.The partition of beta diversity showed that the turnover component played a major role in the process of waterbird metacommunity assemblage.It was found that the earlier flood recession reduced the richness,abundance in different stages of flood recession,which also increased the turnover of waterbirds.Metacommunities with high habitat heterogeneity had better resistance to abnormal hydrological regime,which resulted in high dissimilarity between and within metacommunities.The results of this study provide important information for waterbird conservation and water level management at shallow lakes in the middle and lower Yangtze River floodplain.

基于MIKE FLOOD的杜家台分蓄洪区运用调度研究

运用MIKE平台建立杜家台蓄洪区行洪道MIKE11一维河道模型,模拟并分析了红星垸堤刨毁前后的分洪道行洪能力。同时搭建MIKE21分洪区二维模型,并利用MIKE FLOOD动态耦合一、二维模块,以此为平台研究杜家台分蓄洪区分蓄汉江夏、秋洪水与长江洪水时的调度工况。结果表明:红星垸堤刨毁后分洪道宽度增加,显著降低了该处分洪道上游的洪水水位,提高了分洪道分洪能力;汉江低量级来水情况下,杜家台只需运用南区1~4垸分洪,而高量级来水下杜家台需运用1~7垸分洪;长江分洪时,处于下游的第6垸分洪能力显著,最终可解除第7、9垸的风险,只需运用1~6垸。现有防洪工程中第5、6垸分洪速度较慢且分洪量小,而处于最上游的第2垸分洪量大且分洪较快,导致与其相临的1~4垸洪水超高,危及7、9垸,故7、9垸堤顶亟待加高,同时5、6垸分洪能力需要增强。

Rainfall-runoff simulation and flood forecasting for Huaihe Basin

The main purpose of this study was to forecast the inflow to Hongze Lake using the Xin＇anjiang rainfall-runoff model. The upper area of Hongze Lake in the Huaihe Basin was divided into 23 sub-basins, including the surface of Hongze Lake. The influence of reservoirs and gates on flood forecasting was considered in a practical and simple way. With a one-day time step, the linear and non-linear Muskingum method was used for channel flood routing, and the least-square regression model was used for real-time correction in flood forecasting. Representative historical data were collected for the model calibration. The hydrological model parameters for each sub-basin were calibrated individually, so the parameters of the Xin＇anjiang model were different for different sub-basins. This flood forecasting system was used in the real-time simulation of the large flood in 2005 and the results are satisfactory when compared with measured data from the flood.

Mathematical model for flood routing in Jingjiang River and Dongting Lake network

The main stream of the Yangtze River, Dongting Lake, and the river network in the Jingjiang reach of the Yangtze River constitute a complex water system. This paper develops a one-dimensional （l-D） mathematical model for flood routing in the river network Of the Jingjiang River and Dongting Lake using the explicit finite volume method. Based on observed data during the flood periods in 1996 and 1998, the model was calibrated and validated, and the results show that the model is effective and has high accuracy. In addition, the one-dimensional mathematical model for the river network and the horizontal two-dimensional （2-D） mathematical model for the Jingjiang flood diversion area were coupled to simulate the flood process in the Jingjiang River, Dongting Lake, and the Jingjiang flood diversion area. The calculated results of the coupled model are consistent with the practical processes. Meanwhile, the results show that the flood diversion has significant effects on the decrease of the peak water level at the Shashi and Chenjiawan hydrological stations near the flood diversion gates, and the effect is more obvious in the downstream than in the upstream.

Stand Structure, Diversity and Regeneration Status of Woody Species in Open and Exclosed Dry Woodland Sites around <i>Molapo</i>Farming Areas of the Okavango Delta, Northeastern Botswana

Stand structure, diversity and regeneration status of woody species were investigated in open and exclosed dry woodland sites in Island Safari, Shorobe and Xobe, northeastern Botswana. A total of 105, 111 and 130 quadrats, measuring 20 × 20 m each, were laid down along parallel line transects in the three sites, respectively, to collect data. A total of 47 species, representing 16 families and 24 genera, were recorded in the study sites. Of these, 33 species representing 13 families and 20 genera, 41 species representing 15 families and 23 genera and 27 species representing 10 families and 14 genera were encountered in Island Safari, Shorobe and Xobe, respectively. The most diverse family was Fabaceae followed by Combretaceae and Tiliaceae at all the three sites. The most diverse genus was Acacia, followed by Combretum and Grewia. The diversity of woody species in the study sites were 2.18, 2.15 and 1.5 in Shorobe, Island Safari and Xobe, respectively, while their corresponding evenness values were 0.6, 0.6 and 0.5, respectively. The mean densities of the woody species encountered in Island Safari, Shorobe and Xobe were 2629, 4271 and 2745 individuals ha&#451, respectively. The five densest species were Colophospermum mopane, Dichrostachys cinerea, Acacia tortilis, Philenoptera violacea and Terminalia prunioides in Island Safari, C. mopane, A. tortilis, A. erioloba, P. violacea and D. cinerea in Shorobe and Acacia mellifera, A. tortilis, P. nelsii, A. luederitzii and A. erubescens in Xobe. The highest important value index values were exhibited by C. mopane, D. cinerea, A. tortilis, P. violacea and T. prunioides in Island Safari, C. mopane, A. erioloba, A. tortilis, P. violacea and C. imberbe in Shorobe, and A. mellifera, A. tortilis, P. nelsii and A. luederitzii in Xobe. The alarming result was the fact that 71%, 80% and 85% of the woody species recorded in Island Safari, Shorobe and Xobe, respectively, exhibited hampered regeneration and, thus, unhealthy population structures. Therefore, there is an urgent need to address the observed unhealthy population structures of the woody species through investigation of the major causes of their hampered regeneration, and also designing measures that will facilitate natural and artificial regeneration of these species at the three study sites.

Comparison of oil displacement mechanisms and performances between continuous and dispersed phase flooding agents

To compare the oil displacement mechanisms and performances of continuous phase flooding agent(traditional polymer solution) and dispersed phase flooding agent(particle-type polymer SMG dispersion), the particle phase separation of SMG dispersion migrating in pores was simulated by using the microfluidic technology. Theoretically guided by the tree fork concentration distribution of red cells in biological fluid mechanics, the concentration distribution mathematical model of SMG in different pores is established. Furthermore, the micro and macro physical simulation experiments of continuous and dispersed phase flooding agents were carried out. The results show that the continuous flooding agent enters all the swept zones and increases the flow resistance in both larger and small pores. On the contrary, the particle phase separation phenomenon occurs during the injection process of dispersed flooding agent. The SMG particles gather in the larger pore to form bridge blinding, and the carrier fluid displace oil in the small pore. Working in cooperation, the SMG particle and carrier fluid drive the residual oil in the low permeability layers step by step and achieve the goal of enhanced oil recovery. The laboratory experimental results indicate that, the oil increment and water reduction effect of dispersed flooding agent is much better than that of continuous flooding agent, which is consistent with the field test results.

Why Does the Repaired Len Small Levee, Alexander County, Illinois, US Continue to Breach during Major Flooding Events?

One only needs to study the soil and geologic history and location of the ancient Mississippi and Ohio Rivers to understand why Len Small levee if patched will continue to fail. Much of Dogtooth Bend located in Alexander County, Illinois was originally in the ancient Ohio River valley (Figure 1) alluvial sediments north and east of the confluence with the ancient Mississippi River. The ancient Ohio River valley soils underlain by alluvial sediments and have been easily eroded by the re-aligning modern Mississippi River which now travels through the bedrock controlled Thebes Gap (Figure 2) and into the Ancient Ohio river valley. The primary objectives of this paper are: 1) to explain why Len Small levee, Alexander County, Illinois, US will continue to breach during major flooding events if repaired and 2) to develop a new combined raised causeway and levee system which will provide a Mississippi River floodwater bypass, be sustainable, encourage and fund a land use change, restore the degraded highway road beds, protect remaining Dogtooth Bend farmsteads and farmland that have not yet been degraded by past flooding events and provide floodwater storage during major flooding events at the confluence of the Mississippi and Ohio Rivers.

Engineering Strategies on Flood Control in Middle Reach of Yangtze River, China

Flood disaster has been a serious hidden danger since the ancient time. The essential cause for the fact that floods have not been eliminated for hundreds of years is that time honored strategies do not suit the cases of flood prevention. In the view of geological environmental analyses of flood formation and from the synthesis of experiences gained in flood control in the past hundreds of years, sluggish draining of flood, silt sedimentation in channel and building levee blindly constitute the main cause of intractable flood for a long time in the middle reach of the Yangtze River. Draining away silt and water is the only way to stamping out flood disaster. Opening up artificial waterways for flood diversion, draining away the silt of channel into the polders, and storing the flood water are important engineering measures for the flood control and damage reduction.

Land Use Change Trajectories for Wetland Management (Mogi-Guaçu Floodplan River, Southern Brazil)

Natural and anthropogenic factors are responsible for changes in wetland function and structure. This research deals with the complexity of interactions among flood attributes, climatic data and land use trajectories to track the impact of land use changes for wetland management, over 30 years (1984- 2014). This paper presents a multi-temporal analysis of a floodplain to know the inter-annual ecohydrological variability, including extraordinary events of floods and droughts, using indicators of hydrological regime. It also presents a quantitative description of the geospatial variability in the Mogi Gua&#231u wetland components to assess the changes in the conversion, replacement, of wetland landscapes by anthropic growth activities. Flood attributes and anthropogenic pressures have altered temporal habitat variability in changes on the river course, in sandbars extent, and oxbow lake genesis and extinction, with a decline in the biota dependent on these habitats. These results have significant implications of the quick expansion of anthropogenic activities and provide key information about the impact of land use changes on the wetland function and structure. It is an objective tool to help the environmental management of wetland areas.

Assessing Land Loss from Flooding in the Lake St. Martin Basin in Manitoba, Canada

Floodwaters from the Assiniboine River are typically diverted to Lake Manitoba and then Lake St. Martin to save the City of Winnipeg and Portage la Prairie from flooding. The four Indigenous communities living Lake St. Martin basin experienced many negative impacts, including long-term displacement after the 2011 flood. Data analysis of historical water levels of Lake Manitoba and Lake St. Martin were conducted to understand the impact of control structures and water levels. Satellite imagery allowed geographic information system (GIS) raster analysis of the shoreline change of Lake St. Martin before and after the 2011 super flood. From 1986 to 2010, the Lake St. Martin area increased slightly by approximately 0.63% but in 2011 the lake area increased by 13%. 11,000 acres were lost mainly around Lake St. Martin First Nation (LSMFN) reserve and the Little Saskatchewan First Nation, as a result and many houses and other buildings (churches, band offices, etc.) flooded in these communities. The shoreline change analysis showed that, in particular, the west and north shoreline of Lake St. Martin lost its beaches and lakefront properties, to become swampland after the 2011 flood. Thousands of Indigenous people were displaced for eight years, as the community could only start to rebuild its infrastructure and houses on higher ground after a government settlement was reached.

基于MIKE FLOOD的蓄滞洪区分洪能力研究

本文基于蓄滞洪区一、二维耦合模型,通过计算不同典型年洪水的蓄滞洪区分洪能力,得到蓄滞洪区最优运用方案。研究结果可为制定科学、合理、可行的蓄滞洪区启用条件提供技术及理论支撑,保障蓄滞洪区的分洪能力,使防洪效果最大化。

南四湖不同起调水位汛期调水风险传导规律

南水北调东线工程通水以来,有效缓解了山东半岛等地的缺水问题,但水资源供需矛盾依然突出,汛期调水将成为解决该矛盾的方式之一。汛期调水时,湖周河道开闸泄洪,非汛期积累于河道中的污染物随水流下泄入湖,使得流域水环境风险显著增加。为科学支撑东线后续工程汛期调水水环境风险管控和探究湖区内部风险传导机制,以南水北调东线调蓄湖泊南四湖上级湖段为例,构建水环境风险空间传导分析模型,计算相邻子湖区处于不同风险状态组合的概率,定量评价汛期调水时南四湖上级湖流域水环境风险状态,探讨丰、平、枯3种水平年起调水位下水环境风险在南四湖上级湖的传导规律。结果表明:丰水年高水位调水时,南四湖上级湖水环境风险值最小,枯水年最大;高、中水位调水时,呈由低风险传导至中风险、再传导至高风险的逐步传导模式,而低水位调水时,风险由低风险直接传导至高风险;以平水年为例,白马河区至万福河区93%概率为低—中风险增强型传导、7%概率为低—高风险增强型传导。

分汊河道对极端洪水的响应研究——以北江伦洲河段为例

为探究分汊河段河流形态和水动力学特性对极端洪水的响应,以北江下游清远伦洲河段为例,通过实地调研、河床演变分析和数值模拟的方法,系统研究了该河段在2022年6月超百年一遇洪水期间水流运动特性,以及洪水后河床冲淤变化、泥沙粒径分布和水位变化情况。结果表明:“22·6”洪水期间,水流主流在惯性作用下向左侧偏转并对伦洲岛岛头区域产生直接冲击,从而造成该区域基础设施损毁严重;水流冲出峡谷后由于流速降低、挟沙能力下降,导致岛头区域和河道右汊淤积严重,河道左汊则呈冲刷态势;由于岛头区域和河道左、右汊流速差异,导致泥沙粒径分布存在差异,其中岛头区域泥沙粒径明显大于左、右汊河床泥沙粒径;“22·6”洪水后由于河床抬升,水位较洪水前明显壅高,左汊分流比增大,在来流为5000 m^(3)/s条件下,岛头上游水位壅高接近1 m,左汊分流比较洪水前增加约16%。

Deep-reinforcement-learning-based water diversion strategy

Water diversion is a common strategy to enhance water quality in eutrophic lakes by increasing available water resources and accelerating nutrient circulation.Its effectiveness depends on changes in the source water and lake conditions.However,the challenge of optimizing water diversion remains because it is difficult to simultaneously improve lake water quality and minimize the amount of diverted water.Here,we propose a new approach called dynamic water diversion optimization(DWDO),which combines a comprehensive water quality model with a deep reinforcement learning algorithm.We applied DWDO to a region of Lake Dianchi,the largest eutrophic freshwater lake in China and validated it.Our results demonstrate that DWDO significantly reduced total nitrogen and total phosphorus concentrations in the lake by 7%and 6%,respectively,compared to previous operations.Additionally,annual water diversion decreased by an impressive 75%.Through interpretable machine learning,we identified the impact of meteorological indicators and the water quality of both the source water and the lake on optimal water diversion.We found that a single input variable could either increase or decrease water diversion,depending on its specific value,while multiple factors collectively influenced real-time adjustment of water diversion.Moreover,using well-designed hyperparameters,DWDO proved robust under different uncertainties in model parameters.The training time of the model is theoretically shorter than traditional simulation-optimization algorithms,highlighting its potential to support more effective decisionmaking in water quality management.

基于补偿水头差的沿江口门引排流量计算方法研究

长江支流口门多建有节制闸,利用涨落潮过程自行引排水,而引排水流态的复杂性使得引排流量过程难以精准确定。以太湖流域杨林塘口门为例,通过分析引排水调度方式及流态特征,发现涨潮时开启中孔闸门引水,内河侧流态复杂且附近水位差别大,而落潮时开启全部闸门排水,外江侧流态复杂且附近水位有所差别。为此,提出了一种基于补偿水头差的沿江口门引排流量计算方法。该方法通过设置系列补偿水头差修正堰流公式中的水位,统计了计算流量与实测流量偏差值,进而建立了流量偏差值与补偿水头差的相关关系,最终确定适宜的补偿水头差,从而建立适宜沿江口门引排流量计算公式。结果表明:利用该方法预测的引水流量误差减小40%~50%,排水流量误差减小3%~6%。相关经验可供工程设计人员及闸管单位运行管理人员借鉴。

引水式电站压力钢管爆裂洪水对厂区影响研究

为研究引水式电站压力钢管发生爆管事故后对厂区建筑物的影响,采用重力相似准则设计了大沫水电站压力钢管爆裂影响区域物理模型,对钢管爆裂事故影响情况开展了系统试验,比较了压力管道局部破裂和完全破裂后爆管水流运动过程的差异,研究了管道完全破裂后不同响应时间和前池水量下爆管水流的水力参数特征。结果表明,压力管道局部破裂与完全破裂时水流流态存在明显差异,对下游建筑物淹没过程和冲击荷载也明显不同。局部破裂时水流沿环向缺口喷出并形成大量散裂水滴覆盖厂房和水处理室,并未对建筑物产生明显冲击荷载;完全破裂后爆管水流直冲下游建筑物,并沿建筑物墙面爬升到较大高度,对建筑物底部产生较大冲击荷载。爆管水流对房屋的最大淹没深度和最大冲击荷载与爆管发生后前池通过压力钢管泄露水量密切相关。爆管事故发生后,缩短响应时间(尽快关闭钢管进口事故闸门),可有效降低各建筑物被淹没的时间。研究结果可为制定引水式水电站压力钢管爆裂事故应急抢修预案提供参考。

基于概率分布优选的水电工程施工初期导流风险率估计

科学准确地评估水电工程施工初期导流风险率为施工导流方案决策提供了重要依据。以往风险模型中施工洪水洪峰的随机分布均假设服从P-Ⅲ分布,这会影响导流风险率的精度和可靠性。首先采用K-S检验法对初拟的施工洪水洪峰概率分布类型进行初选,并通过RRMSE、M MAE、QQD值的拟合优度综合评比优选最佳概率分布;然后综合考虑水文、水力随机性,构建基于概率分布优选的施工初期导流风险率计算框架,并给出采用Monte-Carlo方法求解风险率的具体流程;最后对国内两座大型水电工程实例进行应用分析。结果表明,风险率计算框架及求解流程是可行的、有效的;I-MED具有一定的拟合能力,可用于导流风险模拟;两个案例的概率分布排序不同、最佳概率分布不同,进而影响导流风险率大小。研究结果有效拓展了施工导流风险理论框架。

漳河分洪口门分洪壅水措施研究

漳河遇50年一遇标准洪水时,分洪口门升斗铺村所在河道滩地较宽,地形较高,为保证分洪规模,需布置分洪壅水设施。文中拟定双堰(主槽堰加滩地堰)、主槽节制闸及双束堤(加主槽堰)3个方案,并从分洪可靠度、调度灵活性、对河道设计洪水位影响、占地及工程投资、管护费用等方面进行了综合分析比较及研究,最终推荐主槽节制闸方案。此次研究成果对类似分洪口门方案的分析具有借鉴意义。