PRELIMINARY STUDY ON FLASH FLOODS IN TARIM RIVER BASIN

Flashfloodsaretheimportanteventsofthehydrologicalregimeofriversinaridareas.IntheTarilncaver(Fig.1),northwesternChina,flashfledarebeingmonitored.TheobSerVeddataandinvestigationdemonstratethedifferenceintime,place,frequencyandintensityoftheiroccurrences.Therearethreet~offlagescommontotheThermcaverbasin.AlmOSteveryyea-rhighwateroccursinmonthesofJuly,AugUstandseptembercausedbyablationrunoff.However,themostdamagingflowSarefromoccasionalflashfindsbyinstenserainstormandglacierlakeoutburstflags(…     

Experimental Study of the Interaction between Building Clusters and Flash Floods

In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.     

Full 2D Hydrodynamic Modelling of Rainfall-induced Flash Floods

Mountain catchments are prone to flash flooding due to heavy rainfall. Enhanced understanding of the generation and evolution processes of flash floods is essential for effective flood risk management. However, traditional distributed hydrological models based on kinematic and diffusion wave approximations ignore certain physical mechanisms of flash floods and thus bear excessive uncertainty. Here a hydrodynamic model is presented for flash floods based on the full two-dimensional shallow water equations incorporating rainfall and infiltration. Laboratory experiments of overland flows were modelled to illustrate the capability of the model. Then the model was applied to resolve two observed flash floods of distinct magnitudes in the Lengkou catchment in Shanxi Province, China. The present model is shown to be able to reproduce the flood flows fairly well compared to the observed data. The spatial distribution of rainfall is shown to be crucial for the modelling of flash floods. Sensitivity analyses of the model parameters reveal that the stage and discharge hydrographs are more sensitive to the Manning roughness and initial water content in the catchment than to the Green-Ampt head. Most notably, as the flash flood augments due to heavier rainfall, the modelling results agree with observed data better, which clearly characterizes the paramount role of rainfall in dictating the floods. From practical perspectives, the proposed model is more appropriate for modelling large flash floods.     

基于洪峰模数的山洪灾害雨量预警指标研究

山洪灾害预警是防御山洪的重要非工程措施,雨量预警指标是山洪灾害预警的关键。目前的雨量预警指标计算方法对水文气象资料条件以及模型建模率定都有很高的要求,并不适用于基层防汛人员。因此,本文基于全国山洪灾害调查评价成果数据,提出了一种运用洪峰模数计算雨量预警指标的简便、易用的方法。该方法以小流域洪水计算推理公式为基础,将公式中流量与流域面积的比值用洪峰模数表示,得到基于洪峰模数的临界雨量估算公式,并考虑流域土壤含水量等因素,分析临界雨量变化阈值,最终得到雨量预警指标。本文以云南省绥江县双河小流域为例,计算结果显示不同时段（1 h、3 h、6 h）净雨量和预警时段呈线性关系。降雨损失计算中洼地蓄水和植被截留在不同时段相同,土壤下渗在不同的时段不相同。在此基础上,计算不同土壤含水量条件下,不同时段的雨量预警指标。最后,对临界流量、降雨损失和预警指标进行了合理性分析,结果显示预警指标和调查评价结果及实测降雨都比较接近,计算的预警指标合理。本研究为基层山洪灾害预警提供了一种快速、便捷的预警指标计算方法,为预警指标计算提供技术支持。     

Extreme Rainfall Events and Associated Natural Hazards in Alaknanda Valley, Indian Himalayan Region

Introduction The Himalaya is considered to be the youngest mountains on the earth, and is tectonically very active, and hence inherently (geologically) vulnerable to hazards. Extreme rainfall events, landslides, debris flows, torrents and flash floods due…     

全国山洪灾害调查评价成果及规律初探

山洪灾害调查评价是1949年来水利行业最大的非工程措施项目,是规模最大的全国性防灾减灾基础信息普查工程,历时4年,涉及全国30个省305个市2138个防治县（区）,国土面积755万km²,人口近9亿。运用普查、详查、外业测量、分析计算等多种手段,掌握了中国山洪灾害防治区范围、人员分布、下垫面条件、社会经济、历史山洪灾害等基本情况,科学分析了山丘区小流域的暴雨洪水特性,评价了现状防洪能力,计算了预警指标,划定了危险区,为山洪灾害预警预报和应急救援决策提供了基础信息支撑。本文系统介绍了全国山洪灾害调查评价的核心要点,综述了调查评价成果,归纳了调查评价成果要素类型,揭示了全国山洪灾害防治区、人口、历史山洪灾害事件与预警能力的空间分布一致性,即山洪灾害各要素集中分布于青藏高原-四川盆地过渡带、川滇交界地区、黄土高原区、东部沿海地区及华北等地区,最后初步探讨了该成果的应用前景。全国山洪灾害调查评价成果将为中国山洪灾害监测预警预报体系建设及防灾减灾能力提升提供丰富的基础数据支撑。     

面向山洪预警的水雨情监测站网布设方法研究

山洪灾害是中国高频发、高死亡率的自然灾害之一。水雨情站网的合理布设及优化,有利于捕获区域暴雨、洪水情势变化的时空异质性,可显著提高中小流域山洪预警的精度,增强山洪灾害防御能力。本文以山洪灾害高发的福建省顺昌县为例,提出了面向山洪预警的水雨情站网布设方法。县内现状雨量和水位站网监测密度分别为37 km²/站和76 km²/站,主要分布在平原主干河流地区,山洪灾害重点防治区内站网布设不足,小流域暴雨山洪监测和预警能力较弱。针对上述问题,综合分析流域降雨时空特征、历史山洪灾害与山洪灾害预警预报需求,对研究区水雨情站网进行了合理性分析和布设研究,建议增设雨量站3座、水位站3座,其中一座水位站同时监测降雨过程,调整后县内雨量站和水位站的监测密度达到34 km²/站和68 km²/站。本文研究对山洪灾害高发区的水雨情站网布设具有参考和指导意义。     

Nash model parameter uncertainty analysis by AM-MCMC based on BFS and probabilistic flood forecasting

A hydrologic model consists of several parameters which are usually calibrated based on observed hydrologic processes. Due to the uncertainty of the hydrologic processes, model parameters are also uncertain, which further leads to the uncertainty of forecast results of a hydrologic model. Working with the Bayesian Forecasting System (BFS), Markov Chain Monte Carlo simulation based Adaptive Metropolis method (AM-MCMC) was used to study parameter uncertainty of Nash model, while the probabilistic flood forecasting was made with the simulated samples of parameters of Nash model. The results of a case study shows that the AM-MCMC based on BFS proposed in this paper is suitable to obtain the posterior distribution of the parameters of Nash model according to the known information of the parameters. The use of Nash model and AM-MCMC based on BFS was able to make the probabilistic flood forecast as well as to find the mean and variance of flood discharge, which may be useful to estimate the risk of flood control decision.     

Using uncertainty and sensitivity analysis for finding the best rainfall-runoff model in mountainous watersheds(Case study: the Navrood watershed in Iran)

In watersheds that have not sufficient meteorological and hydrometric data for simulating rainfall-runoff events, using geomorphologic and geomorphoclimatic characteristics of watershed is a conventional method for the simulation. A number of rainfall-runoff models utilize these characteristics such as Nash-IUH, Clark-IUH, Geomorphologic Instantaneous Unit Hydrograph(GIUH), Geomorphoclimatic Instantaneous Unit Hydrograph(GcIUH), GIUH-based Nash(GIUH-Nash) and GcIUH-based Clark(GcIUH-Clark). But all these models are not appropriate for mountainous watersheds. Therefore, the objective of this study is to select the best of them for the simulation. The procedure of this study is: a) selecting appropriate rainfall-runoff events for calibration and validation of six hybrid models, b) distinguishing the best model based on different performance criteria(Percentage Error in Volume(PEV); Percentage Error in Peak(PEP); Percentage Error in Time to Peak(PETP); Root Mean Square Error(RMSE) and Nash-Sutcliffe model efficiency coefficient(ENS)), c) Sensitivity analysis for determination of the most effective parameter at each model, d) Uncertainty determination of different parameters in each model and confirmation of the obtained results by application of the performance criteria. For application of this procedure, the Navrood watershed in the north of Iran as a mountainous watershed has been considered. The results showed that the ClarkIUH and GcIUH-Clark are suitable models for simulation of flood hydrographs, while other models cannot simulate flood hydrographs appropriately. The sensitivity analysis shows that the most sensitive parameters are the infiltration constant rate and time of concentration in the Clark-IUH model. Also, the most sensitive parameters include the infiltration constant rate and storage coefficient in the GcIUHClark model. The Clark-IUH and GcIUH-Clark models are more sensitive to their parameters. The Latin Hypercube Sampling(LHS) on Monte Carlo(MC) simulation method was used for evaluation of uncertainty of data in rainfall-runoff models. In this method 500 sets of data values are produced and then the peak discharge of flood hydrographs for each produced data set is simulated with rainfall-runoff models. The uncertainty of data changes the value of simulated peak discharge of flood hydrograph. The uncertainty analysis shows that the observed peak discharges of different rainfall-runoff events are within the range of values of simulated by the six hybrid rainfall-runoff models and IUH that inputs of these models were the produced data sets. The range of the produced peak discharge of flood hydrographs by the Clark-IUH and GcIUH-Clark models is wider than those of other models.     

接入实时降雨数据的暴雨型洪涝灾害临灾预警方法

针对现有暴雨型洪涝灾害预警方法时效性差的问题,提出了一种接入实时降雨数据的暴雨型洪涝灾害临灾预警方法。根据时序分析模型由历史降雨数据和实时降雨数据分析识别异常降雨,并将异常降雨、地形起伏、高程和河网因素作为影响因子,构建暴雨型洪涝灾害风险指数,以"日"为时间尺度进行短时暴雨型洪涝灾害风险分析。从异常降雨致灾角度出发,根据降雨的异常程度将暴雨型洪涝灾害风险等级划分为无风险、低风险、中风险、中高风险和高风险5个等级,进而实现临灾预警,为防灾减灾提供一定的参考信息。以广东省清远市2014年5月的洪涝灾害为例,接入5月21日至5月26日期间逐日降雨量数据,实现了临灾风险分析。实验结果表明,六日内清远市阳山县中下区域发生暴雨洪涝灾害的风险较大,与实际灾情相吻合,达到了较好的预警效果。     

城市暴雨内涝模拟模型优化与精度验证

本文采用“Vegetation-Impervious Surface-Soil”模型和线性光谱混合分解方法,获取像元中不透水面、植被、土壤覆盖信息,用于计算SCS模型产流参数综合CN（Curve Number）值;基于土地利用类型,采用经验值与数值实验逐步求精相结合的方法,确定水动力汇流模型参数曼宁系数,并用实测积水数据验证两次参数修正的模拟效果。以上海中心城区为例进行验证,研究结果表明：①将采用V-I-S模型得到的不透水面、植被、土壤信息设定CN值,能够降低积水分布的极值化现象,提高SCS产流模型产流量和产流分布精度;②采用经验法和数值模拟逐步求精法,按土地利用类型设定曼宁系数,使各时段最大积水深度高于原模型,说明曼宁系数是汇流模型的敏感参数。     

BASIC CHARACTERISTICS AND CONTROLLING FACTORS OF ANASTOMSING FLUVIAL SYSTEMS

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｔｅｒｍ“ａｎａｓｔｏｍｏｓｉｎｇｒｉｖｅｒ”ｗａｓｆｉｒｓｔａｐｐｌｉｅｄｂｙＳＣＨＵＭＭ ( 1968) ,ｒｅｆｅｒｒｅｄｔｏｓｔａｂｌｅ ,ｌｏｗｂｅｄ ｌｏａｄ ,ｍｕｌｔｉｐｌｅｃｈａｎｎｅｌｓｙｓｔｅｍｗｉｔｈｌｏｗ ｇｒａｄｉｅｎｔ,ｈｉｇｈｓｉｎｕｏｓｉｔｙａｎｄｓｅｐａｒａｔｅｄｖｅｇｅｔａｔｅｄｉｓｌａｎｄｓ .Ｔｈｉｓｓｐｅｃｉｆｉｃｍｅａｎｉｎｇｏｎ“ａｎａｓｔｏｍｏｓｉｓ”ｗｈｉｃｈｗａｓｆｉｒｓｔｕｓｅｄｂｙＪａｃｋｓｏｎｉｎ 1834ｅｎｄｅｄｔｈｅｓｙ…     

粗糙集在洪水风险评估中的应用

针对洪水灾害事故的随机性,复杂性和不确定的特点,以及在洪水风险评估选取评估指标过程中存在的主观性,通过采用粗糙集的改进属性约简算法对用于评估的指标集进行约简,从而剔除其中的对最终结果不造成影响的指标,并且利用相对约简建立用于洪水风险评估的层次指标体系,应用模糊层次分析法对该地区的洪水风险进行评估,比单纯的依靠专家打分法更具有科学依据和数据支持。     

Response of the distributary channel of the Huanghe River estuary to water and sediment discharge regulation in 2007

The water and sediment discharge regulation (WSDR) project, which has been performed since 2002 before flood season every year, is of great significance to the river management in China. Until 2007, six experiments have been fulfilled to evaluate the effect of the project on the natural environment. To fill the gap of investigations, a study on flood and suspended sediment transportation and channel changing along the distributary channel of the Huanghe (Yellow) River was conducted during the WSDR project period in 2007. The lower channel was scoured rapidly and the channel became unobstructed gradually several days after the flood peak water was discharged from the Xiaolangdi Reservoir. Within four days after the flood peak at 3 000 m³/s entered the distributary, the channel in the river mouth area was eroded quickly. Both the mean values of area and depth of the main channel were tripled, and the maximum flood carrying capacity increased to 5 500 m³/s or more. Then, the river channel was silted anew in a very short time after completion of the WSDR. Favored by the WSDR project, the river status in April 2008 became better than that of the year before. The adjustment ranges of main channel parameters were about 30%, 10%, and 10% at sections C2, Q4, and Q7, respectively. The process of rapid erosion-deposition was more active 15 km away in the channel from the river mouth due to the marine influence. It is reasonable for discharging sediment at concentration peak from Xiaolangdi Reservoir at the end of the flood peak. As a result, the sediment peak reached the river mouth about two days later than that of the water current. In addition, the WSDR project has improved the development of the estuarine wetland. Wetland vegetation planted along the river banks restrained the water flow as a strainer and improved the main channel stability. It is suggested to draw water at mean rate of 150 m³/s from the Huanghe River during flood periods, because at the rate the water in the wetland would be stored and replenished in balance. Moreover, we believe that cropland on the river shoal of the lower Huanghe River should be replaced by wetland. These activities should achieve the Huanghe River management strategy of “To concentrate flow to scour sediment, stabilize the main channel, and regulate water and sediment”.     

基于F-DEM的洪水淹没区精确快速提取

洪水淹没区包括洪水淹没的范围与深度,准确、高效地获取洪水淹没区是洪灾评估及减灾救灾的关键。本文针对现有洪水淹没范围与深度的快速计算及精度方面的不足,设计了洪水淹没区精确快速提取方法。首先,通过特征嵌入式DEM(F-DEM)数字地形建模技术,修正常规格网DEM对沟渠、坎堤等突变地形描述的失真问题;然后,基于洪水水位监测数据,采用Kriging内插模型构建洪水淹没面;最后,通过GIS多层面叠加及空间查询分析,获取真实淹没区信息。以温州水头镇水位监测点数据为基础,对其暴风潮后的洪水淹没区进行了分析,并利用大区域模拟水位监测点数据对提取方法效率作了测试。实验结果表明,该方法能较好地解决大区域海量数据条件下的淹没区提取问题。     

青岛市大沽河流域防汛信息系统

随着计算机信息技术在水利学科中应用的深入,以及数字水利、数字流域概念的提出,水利信息化已经成为这一行业领域的主要发展方向,各种流域模型在与地理信息系统平台结合后在数据的收集、存储,提取与处理的基础上都有了很大的发展,在水利工程的规划设计、防洪减灾、水量分配等方面有更为广泛的应用。青岛市大沽河流域内洪水有来势猛、峰高量大和暴涨暴落的特性,为满足防汛管理部门对洪水预测及相关信息快速浏览查询的需求,建立了青岛市大沽河流域防汛信息系统。该系统在MAPX地理信息系统开发软件、数据库存储技术和水流数学模型的支持下,实现了大沽河流域的地理信息、水文信息以及其他信息的综合管理,同时通过水流数学模型对一维和二维洪水进行预测预报,并根据用户的需要完成所需的查询与分析功能,以最直观简洁的方式向用户展示系统的输出结果。系统数据库的开发在满足系统要求的基础上完成了与青岛市雨情水情自动监测系统的对接,保证了水文数据的实时性、完整性和准确性。系统集成了一维非恒定流模型与平面二维非恒定流水流模型,可以根据大沽河流域降雨量计算干流的水位变化以及发生溃堤后洪水的淹没过程。应用表明,该系统界面友好、功能完善、性能良好,具有很强的实用性。     

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Application and comparison of coaxial correlation diagram and hydrological model for reconstructing flood series under human disturbance

Intense human activities have greatly changed the flood generation conditions in most areas of the world, and have destroyed the consistency in the annual flood peak and volume series. For design flood estimation, coaxial correlation diagram and conceptual hydrological model are two frequently used tools to adjust and reconstruct the flood series under human disturbance. This study took a typical mountain catchment of the Haihe River Basin as an example to investigate the effects of human activities on flood regime and to compare and assess the two adjustment methods. The main purpose is to construct a conceptual hydrological model which can incorporate the effects of human activities. The results show that the coaxial correlation diagram is simple and widely-used, but can only adjust the time series of total flood volumes. Therefore, it is only applicable under certain conditions (e.g. There is a strong link between the flood peaks and volumes and the link is not significantly affected by human activities). The conceptual model is a powerful tool to adjust the time series of both flood peak flows and flood volumes over different durations provided that it is closely related to the catchment hydrological characteristics, specifically accounting for the effects of human activities, and incorporating expert knowledge when estimating or calibrating parameters. It is suggested that the two methods should be used together to cross check each other.     

基于元胞自动机模型的河道汇流过程模拟

对河道汇流过程进行模拟可为洪水灾害预警预报提供参考。利用水力水文学方法能很好地模拟河道汇流过程,但需要输入的参数多,运算过程复杂,对数据精度要求高,而且在无资料区流域无法确定河道上断面流量情况下,该方法具有一定局限性。本文将元胞自动机模型与水文模型相结合,构建了河道汇流过程中的元胞自动机模型和产流汇流规则。通过建立河道坡面拓扑关系,利用SCS-CN（Soil Conservation Service-Curve Number）模型逐个计算河道元胞上的坡面入流,并利用曼宁方程模拟河道汇流过程,最后在ArcEngine平台下进行二次开发,实现了河道汇流可视化。本文以厦门市茂林溪流域为研究区,对1997年5月6日至7日的一场降雨进行了模拟。将本文模拟结果与该流域其他学者的研究进行了对比分析,结果表明在输入数据与水文模型参数相同的情况下,本文不仅模拟出每次降雨间隔产生的较小洪峰,并且整场降雨产生的最大洪峰流量精度与时间精度均提高了5倍,可以更准确地模拟河道汇流过程,适用于河道汇流可视化,该模拟可以为洪水灾害预警预报提供一定参考。     

长江上游洪涝暴雨环流形势中期演变趋势分析

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