沙丘前沿区产汇流特点研究及其在设计洪水计算中的应用

对沙丘前沿区的产汇流机制进行了探讨,分析地表产流面积随着降雨量不同而发生动态变化的规律,研究该区域的设计洪水计算新方法.其结果为沙丘出流河流的相似流域设计洪水计算提供借鉴.     

皇甫川流域次洪水沙特征值变化特点

黄河流域径流量呈现锐减趋势,径流锐减突出表现在中游河口镇至龙门区间。以河龙区间皇甫川流域为典型支流,选择19542012年洪峰流量大于100m3/s的洪水共271场,分析了次洪水沙特征值的变化。得出如下结论:近些年洪水发生次数和年最大洪峰流量高值出现次数均有减少趋势;次洪洪量和次洪沙量基本呈现逐年代减少的趋势,沙量减少幅度远大于洪量的减幅;涨洪历时比较短,峰型普遍偏尖瘦;洪峰流量大的洪水的基流量占洪量的百分比明显低于洪峰流量小的洪水对应的比值。     

High resolution records of flood deposition in the mud area off the Changjiang River mouth during the past century

This paper presents a paleoflood study to determine the flood frequency of the Changjiang River, based on core cj0702, taken from the Changjiang River subaqueous delta. We identified flood deposits by means of high-resolution grain-size variation, sensitive population, geochemical indexes and magnetic susceptibility. The core covers a time span of 120 years by 210 Pb dating and was sampled at 1–2 cm intervals. Grain size, geochemical elements, and physical parameters were analyzed. The results indicate that the sediment of the core is mainly composed of silt and clay, as well as groups of interbedded silt, clay silt, and clay. Vertically, the grain size pattern was controlled by seasonal variations in water discharge and by the sediment input in winter from the abandoned Huanghe River delta. River flooding caused extreme values in all our measured parameters. We identified more than 20 flood events that occurred since 1887 using the physical parameter analysis method. The environmentally sensitive component of sediment grain size(14.32–96.39 μm) contribution30%, Zr/Rb ratio1.5, and magnetic susceptibility16 were selected as the criteria for flood identification generally. We also found that floods that had taken place in the upstream, midstream, or downstream parts of the river were clearly identified by these indexes while the large-scale floods that covered the whole drainage area did not leave clear indications in the sediment record. This study for identification of flood events is of great significance for understanding hyperpycnal current sedimentation as well as for forecasting of floods.     

Simplified Wave Models Applicability to Shallow Mud Flows Modeled as Power-Law Fluids

Simplified wave models- such as kinematic,diffusion and quasi-steady- are widely employed as a convenient replacement of the full dynamic one in the analysis of unsteady open-channel flows,and especially for flood routing.While their use may guarantee a significant reduction of the computational effort,it is mandatory to define the conditions in which they may be confidently applied.The present paper investigates the applicability conditions of the kinematic,diffusion and quasisteady dynamic shallow wave models for mud flows of power-law fluids.The power-law model describes in an adequate and convenient way fluids that at low shear rates fluids do not posses yield stress,such as clay or kaolin suspensions,which are frequently encountered in Chinese rivers.In the framework of a linear analysis,the propagation characteristics of a periodic perturbation of an initial steady uniform flow predicted by the simplified models are compared with those of the full dynamic one.Based on this comparison,applicability criteria for the different wave approximations for mud flood of power-law fluids are derived.The presented results provide guidelines for selecting the appropriate approximation for a given flow problem,and therefore they may represent a useful tool for engineering predictions.     

三维GIS蓄滞洪区淹没分析与灾损评估

蓄滞洪区是江河防洪体系的重要组成部分.基于洪水淹没机理,通过对蓄滞洪区地表的连通性分析,构建淹没过程模型;用等量分析的思想建立了计算洪水淹没水深和淹没范围的淹没分析模型,并在三维GIS环境中实现淹没分析结果的三维动态可视化.将淹没分析结果与社会背景数据叠加,结合洪灾损失率,对淹没区内的各类资产进行洪灾损失评估,为蓄滞洪区的管理、防洪减灾决策提供快捷、直观形象的信息支持.     

长白山天池火山溃湖洪水最大流量的初步估算及影响分析

长白山天池火山是目前最具潜在喷发危险的活火山。依据长白山天池火山的最新监测研究成果,结合地形地貌、水文流域特点及天池火山历史喷发类型,重点分析了长白山天池火山未来喷发时发生溃湖洪水的危险性。利用相关的水动力学公式,建立了溃口规模和洪水湿周、流量和流速的内在关系。详细分析溃湖洪峰在下游二道白河镇、白山水电站、红石水电站等关键位置的最大流量及流速。结果表明,若天池火山湖水溃泄一半即10亿m3时,距火山口50km处的二道白河镇瞬时洪水流速达84 904m3/s,该镇将全部被淹没。下游的白山水库、丰满水库将分别受到流量23 560m3/s和1 505m3/s洪水的冲击,水库安全受到严重威胁。     

The hydrological effect between Jingjiang River and Dongting Lake during the initial period of Three Gorges Project operation

Based on the measured hydrological data from 1951 to 2008, the chain hydrological effect between Jingjiang River and Dongting Lake is analyzed by comparative method after the Three Gorges Project operation. The result indicates that 1) the scouring amount in Jingjiang River made up 78.9% of the total from Yichang to Chenglingji, and its average scouring intensity was higher than the latter; 2) the water and sand diversion rates at the three outlets of the Jingjiang River were reduced by 2.33% and 2.78% separately; 3) the proportion of multi-year average runoff and sediment through the three outlets in the total into the Dongting Lake decreased by 7.7% and 24.4% respectively; 4) in Dongting Lake, the speed of sediment accumulation was lowered by 26.7%, in flood season, the runoff amount was 20.2% less than the multi-year average value, leading to seasonal scarcity of water year by year. The former prolonged the lake life, while the latter induced droughts in summer and fall in successive years, shortage of drinking and industrial water, shipping insecurity, as well as ecological problems such as decrease of birds and quick increase of Microtus fortis; 5) The multi-year average values of sediment and flood transporting capacity at the lake outlet were respectively increased by 26.6% and 3.7%, the embankments were protected effectively. Then, to adapt to the new change of the river-lake relation, some suggestions were put forward, such as optimizing further operation program of the Three Gorges Reservoir, reexamining the idea of river and lake regulation, and maintaining connection of the river and the lake.     

汛期洪水资源化利用对三峡水库淤积影响研究

作为三峡水库诸多优化调度方式中的一种,洪水资源化利用对水库淤积的影响受到持续关注,开展针对场次洪水的相关研究有助于进一步深化对水库淤积科学问题的认识,有望为调度工作提供一定的技术支撑。通过2013年以来的历史水文资料分析与水沙运动数值模拟,探究了入库洪水的输沙过程以及洪水资源化利用对库区淤积与水库排沙的影响。结果表明:洪峰流量介于30000～55000 m3/s的中小洪水是近年三峡入库洪水的主要形式,随着入库洪峰流量的增加,洪水的地区组成逐渐趋向于金沙江下游、嘉陵江共同主导;常年回水区淤积、水库排沙是“消化”入库泥沙的两种主要途径,且以前者的作用为主;针对Ⅰ-3类入库洪水,坝前起调水位Z₀的抬升或洪水资源化利用对水库淤积的影响主要在于造成了库区淤积的重分布,次要在于改变了水库的排沙作用,在Z₀≤150 m条件下,洪水资源化利用对水库淤积的影响相对较小;针对典型洪水,当武隆洪峰流量Q’_WL与入库洪峰流量Q’_RK的比值小于1/5(即Q’_WL/Q’_RK<1...     

扩域搜索遗传算法优化马斯京根参数及其应用

马斯京根法作为河道洪水预报的重要方法,参数和系数的率定是关键和难点,直接影响其预报精度。在详细阐述扩域搜索遗传算法基本思想和性能分析的基础上,以模拟结果与实测值的误差最小作为进化目标,直接搜索马斯京根法预报方程系数,获得河道上下游流量关系方程。对黄河下游夹河滩至高村的洪水过程进行研究,传统方法的平均绝对误差为240 m³/s,平均相对误差为0.13;遗传算法的平均绝对误差为95 m³/s,平均相对误差为0.05。结果表明：遗传算法精度明显高于传统方法。在实际应用中,对于河道洪水波的传播规律性变化较大的河道,应根据不同量级洪水来模拟洪水的传播规律,并对相应量级的洪水进行预报。     

中原地区4 ka BP前后异常洪水事件的沉积证据

国内外考古学和第四纪地质学研究的大量证据表明,4000 a BP前后是史前洪水频发的时期,这次史前洪水事件的性质、规模、起因以及它对人类文化演进的影响一直是国际学术界关心的问题。我国有关4000 a BP前后史前洪水的研究始于20 世纪90 年代,在随后的十几年间,先后在青海喇家遗址、河南新寨遗址、锉李遗址、孟县遗址、山东尹家城遗址等处发现了这次洪水事件的地质和考古遗迹。这些古洪水遗迹的发现,受到国内外学者的高度重视。中原地区是华夏文明的发祥地,尽管这一地区4000 a BP前后洪水事件的遗迹已有发现,但数量偏少,研究程度不够深入,远不能满足人们对古洪水、古气候研究的需求,也不能满足对华夏文明起源研究的需求。为此,在过去工作基础上,结合最新的考古发掘,我们近年来继续在中原地区开展4000 a BP古洪水的研究,相继发现了多处这次洪水事件的地质和考古记录,其中以河南西部的偃师二里头遗址、河南北部的焦作西金城遗址和山西南部的绛县周家庄遗址最具代表性。这三处遗址分别位于不同的地貌部位,研究表明,以上三处出现的史前洪水,都与当时比较湿润的气候环境有关,同时,受地貌条件的影响,它们又具有不同的洪水过程,对人类的影响也存在一定的差异。