强人类活动平原地区河网提取中的流路强化方法

我国北方强人类活动平原地区的水资源问题越来越严峻,基于分布式水文模型的水循环模拟是流域水资源研究的基础,其中基于DEM的河网水系提取是基础环节。平原地区由于沟谷发育不明显,且人工河道和沟渠众多,流域汇流结构支离破碎,常用的河网提取模型往往很难得到正确的结果。本文借助已有的主要干流数字化河网水系,提出了流路强化处理方法,用于对平原地区的DEM进行预处理,经过处理后的DEM输入河网提取模型,可以得到流路正确、且河网密度更精细的河网水系拓扑结构,为分布式水文模型的高精度水文单元划分奠定基础。该方法在强人类活动干扰的典型流域——海河流域进行了应用,对比了流路强化处理前后的河网提取结果,表明该方法是一种方便、快捷、高效的处理方法。     

适用于大尺度水文气候模式的DEM洼地填充和平坦区处理的新方法

针对传统的DEM(Digital Elevation Model)洼地和平坦区处理方法存在的速度慢等问题,提出了新的DEM处理方法。新方法由两个新算法组成:其一为DEM快速分位数分类算法,此算法先利用DEM的统计特征计算出分位数,然后分类,其时间复杂度仅为O(N),速度远大于传统分类方法的O(NlogN);其二为对分类后洼地和平坦区处理的新算法,此算法从高程最小的一类开始逐类处理,直到处理结束。用90m DEM对不同方法进行评价的结果表明:新方法在保证结果准确性前提下显著提高了DEM洼地和平坦区的处理效率。而且,新方法除了可将洼地填平之外,还可对洼地增加微小高程,生成无平坦区的DEM。新方法已成功地应用到地形指数的计算及TOPMODEL水文模拟,还适用于基于DEM的大尺度水文气候模拟与分析。     

基于数字高程模型的河网提取及子流域生成

提出新的从DEM直接提取河网与划分子流域的方法(AEDNM)。该方法与以往方法的不同之处在于不再对DEM进行填洼处理，而是结合图论与水文学的思想，从流域的出口直接向上游搜索，通过图的遍历来确定流向，使全流域形成一个有向无环图，这样提取的河网可以保证是连续的，同实际河网误差很小。根据河网划分的子流域大小也基本均匀，能够满足水文模型模拟的需求。经过黄河、泾河与白河流域的算例验证，表明该法简单可行。     

Comparison of two different methods for determining flow direction in catchment hydrological modeling

Digital elevation models (DEMs) are widely used to define the flow direction in distributed hydrological models for simulation of streamflow. In recent decades, numerous methods for flow direction determination have been applied successfully to mountainous regions. Nevertheless, some problems still exist when those methods are used for flat or gently sloped areas. The present study reviews the conventional methods of determining flow direction for such landscapes and analyzes the problems of these methods. Two different methods of determining flow direction are discussed and were applied to the Xitiaoxi Catchment, located in the Taihu Basin in southern China, which has both mountainous and flat terrain. Both the agree method and the shortest path method use drainage networks derived from a remote sensing image to determine the correct location of the stream. The results indicate that the agree method provides a better fit with the DEM for the hilly region than the shortest path method. For the flat region where the flow has been diverted and rerouted by land managers, both methods require observation of the drainage network to determine the flow direction. In order to clarify the applicability of the two methods, both are employed in catchment hydrological models conceptually based on the Xinanjiang model and implemented with PCRaster. The simulation results show that both methods can be successfully applied in hydrological modeling. There are no evident differences in the modeled discharge when using the two methods at different spatial scales.     

数值地形图的生成及其水文地貌特征评价

数值地形图(DEM)是利用地理信息系统(GIS)进行流域水文模拟的基础, 其精度直接影响模拟结果在没有现成的数值地形图时, 应用人员往往利用传统的地形图来生成它. 本文分别采用Arc/Info地理信息系统软件提供的哈奇逊法和不规则三角网五次插值法, 对一个实验流域的高程取样点进行插值, 生成了4种不同的数值地形图, 从凹洼分布、流域界定、河网提取、地面坡度和地形指数、以及地面径流汇成等方面, 对它们的水文地貌精度进行了比较. 结果表明, 两种方法都能生成由高程点群所反映的地形, 然而由于哈奇逊法能够结合流域的河网结构及其具有物理基础的水文地貌加强法来处理凹洼问题, 因此大大地提高了其所生成的流域数值地形图水文地貌特征精度.     

复杂下垫面城市暴雨内涝汇水区划分方法研究

汇水区(catchment)是径流控制的结构单元,也是水文模型中重要的输入数据。在城市地区,由于复杂的下垫面特征,使用传统的汇水区划分方法得到的结果和现实情况差异较大。在已有的汇水区划分方法基础上,结合城市地区实际径流特点,提出了新的汇水区划分方法。首先,将影响地表汇流路径的不同地物高程信息融入到DEM中;然后,对概化后的排水管网进行缓冲区分析并修正对应范围内的DEM数据,进一步优化DEM;再次,结合研究区范围确定合适的DEM空间分辨率,保证子汇水区划分的合理性;最终,根据精细化的DEM数据,利用D8算法划分子汇水区。以海宁地区为研究区,并将新方法与3种传统方法进行对比。结果表明:细化后的DEM能够更加真实地反映地表高程,汇水区划分结果可以准确刻画地表径流过程,提高了汇水区划分的合理性。     

数字化水系辅助 DEM 提取 Karst 地区水系的应用研究

近年来,分布式水文模型与 GIS 密切结合已经成为水文预报的研究重点和热点,其中基于 DEM 提取某一流域的水流方向矩阵是其核心之一。然而在中国南方 Karst 地区具有地表和地下二元空间结构,地表有大量的洼地与漏斗和溶洞发育,如果用填洼的常规方法则改变了 Karst 地区真实栅格单元的水流方向,造成大量的平坦地区,而且提取出的水系有大量平行水系与河道的缺失。因此,利用数字化河网修正 DEM 后无需填洼就能提取出接近 Karst 地貌背景下的真实水系,提取出的水系中几乎没有平行水系和河道的缺失 , 而且正确地引导了局部栅格单元的水流流向。用该方法提取的水系对建立 Karst 地区更高精度的分布式水文模型具有很好的应用价值。     

涪江通口河流域河网提取及唐家山溃流洪水模拟分析

基于美国Global Land Cover Facility（GLCF）的2004．3 Arc Second SRTM Elevation全球90m精度的DEM数据源,采用作者开发的DEM凹陷区域识别与处理、河网自动生成与流域划分软件,提取了四川省唐家山堰塞湖所在涪江通口河流域河网相关信息。采用具有高分辨率及高稳定性能格式精度的二维水动力学模型,将两种估算的唐家山堰塞湖溃决流量过程作为输入,估算了唐家山堰塞湖以下涪江通口河流域的洪水过程与低洼地的洪水淹没过程。结果表明,从公开的高分辨率全球DEM数据自动提取指定流域信息,采用二维水动力学模型模拟流域尺度突发洪水淹没过程的模型系统,可以快速、便捷地模拟不同流域的洪水演进过程,可为国家的洪水灾害防治分析提供实用和可靠的技术工具和手段。     

基于栅格DEM 的沙兰河流域河网提取及局地暴雨洪水模拟

本文基于美国Global Land Cover Facility（GLCF）的全球90m精度的DEM数据源，采用作者开发的DEM凹陷区域识别与处理、河网自动生成与流域划分软件，提取了黑龙江省沙兰镇以上沙兰河流域河网相关信息。同时结合沙兰河暴雨洪水的相关报道，采用内含简化水文过程的二维水动力学模型，直接用假设的降水过程作为输入，估算了沙兰河流域局地暴雨的洪水过程与低洼地的洪水淹没过程。结果表明，从公开的高分辨率全球DEM数据自动提取指定流域信息，并利用降雨数据作为模型输入，采用上述模型，可以为山洪灾害防治分析提供有力的技术工具和手段。     

Assessing Impact of Flood on River Dynamics and Susceptible Regions: Geomorphometric Analysis

Natural climatic hazards like flood, an important hydro-geomorphic process of earth’s surface, have different regional and local impacts with significant socio-economic consequences. Similar was the case in Gujarat State, India during last week of June 2005. This study is about assessing the impact of Gujarat flood on river dynamics. It deals with extraction of water bodies information using radiance image and standard water indices i.e., Normalized Difference Water Index (NDWI) and Modified Normalized Difference Water Index (MNDWI) for pre- and post-flooding periods. Geomorphometric analysis along with drainage network extraction was done using two different Digital Elevation Models (DEMs) i.e., Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topographic Mission (SRTM) and compared. Finally, depressions mapping and comparative analysis of magnitude and directional change of drainage networks was carried out. Results confirmed better accuracy of MNDWI in separating water bodies. The water bodies area increased by 10.4 % in post-flood monsoon compared to pre-flood monsoon and by 3.8 % in post-flood dry season compared to pre-flood dry season. Geomorphometric analysis indicated that ASTER DEM gave more values of maximum slope, average slope, and standard deviation as compared to SRTM. Aspects distribution algorithm did not work well in low relief regions. The drainage network generated using SRTM DEM was more accurate. The depressions identified were more susceptible to flood events. Change analysis of drainage network (deviating 100–300 m) indicated that 5.22 % points deviated between October, 2004 and 2005 and 3.18 % between February, 2005 and 2006.     

石湾站排灌结合新型布置形式的实践与思考

排水和灌溉是平原湖洼区泵站的主要功能。泵站枢纽布置往往需要把二者结合起来,以充分发挥泵站的作用。石湾站枢纽布置提出了灌溉出水涵与已有泵站建筑物结构相结合的新型布置形式,既解决了排灌结合站共用排涝涵洞问题,又解决了灌溉涵基础下回填土质量控制不严引发不均匀沉降大的问题,保障了泵站正常运行,可为类似泵站布置设计提供参考。     

中小城市排水系统排水能力和内涝特性分析——以涡阳县为例

随着城市化进程的加快,城区不透水面积逐渐增加,大多数中小城市的排水管网建设标准相对滞后,中小城市面临严重的内涝风险,研究城区产汇流特性对于城市内涝防治具有十分重要的意义。本文以涡阳县南城区为研究对象,首先利用临近地区水文资料、高精度的遥感影像和DEM共享数据,借助ArcGIS平台和SWMM开源软件,通过综合径流系数法对模型进行率定,并从综合径流系数、降雨径流产汇流关系和实测降雨产生的积水深度对模型进行验证,分析研究区典型暴雨下的管网满管和积水情况,评估排水系统的排水能力和城区的内涝风险。然后,对内涝严重区域进行有针对性的内涝分析,并分析低影响开发措施对城区内涝的影响。结果表明:(1)排水系统在暴雨降雨重现期0.5a及以下,基本可以满足排涝要求;排水系统在暴雨降雨重现期1a及以上,均不能满足排涝要求。(2)低影响措施对城区内涝有很好的缓解作用。该研究方法可为资料缺乏地区,尤其是中小城市内涝分析和防洪减灾提供参考。     

基于快速傅立叶变换（FFT）的地形剖面线的数学表达研究

在数字地形分析中,地形剖面的分析方法不仅可以以线代面研究区域的地形起伏变化,还可很好地反映地形沿某一方向的地势起伏和坡度陡缓,其地形剖面线的数学表达更能为今后的数字地形分析提供坚实的数学基础。鉴于此,将信号分析中常用的傅立叶变换引入到地形剖面分析中,从信号分析的角度,把地形剖面线看成一维连续空间域信号,并对其傅里叶变换后的频谱进行研究分析。通过对地形剖面的频谱分析,可得到该地形剖面所包含的地形频率信息,进而实现地形剖面的数学表达。     

Estimation of Sediment Yield and Areas of Soil Erosion and Deposition for Watershed Prioritization using GIS and Remote Sensing

A Geographical Information System (GIS) based method is proposed and demonstrated for the identification of sediment source and sink areas and the prediction of sediment yield from watersheds. Data from the Haharo sub-catchment having an area of 565 km² in the Upper Damodar Valley in Jharkhand State in India was taken up for the present study due to availability of gauged data at multiple locations within watershed area. The watershed was discretized into hydrologically homogeneous grid cells to capture the watershed heterogeneity. The cells thus formed were then differentiated into cells of overland flow regions and cells of channel flow regions based on the magnitude of their flow accumulation areas. The gross soil erosion in each cell was calculated using the Universal Soil Loss Equation (USLE). The parameters of the USLE were evaluated using digital elevation model, soil and landuse information on cell basis. The concept of transport limited sediment delivery (TLSD) was formulated and used in ArcGIS for generating the transport capacity maps. An empirical relation is proposed and demonstrated for its usefulness for computation of land vegetation dependent transport capacity factor used in TLSD approach by linking it with normalized difference vegetation index (NDVI) derived from satellite data. Using these maps, the gross soil erosion was routed to the watershed outlet using hydrological drainage paths, for derivation of transport capacity limited sediment outflow maps. These maps depict the amount of sediment rate from a particular grid in spatial domain and the pixel value of the outlet grid indicates the sediment yield at the outlet of the watershed. Up on testing, the proposed method simulated the annual sediment yield with less than ±40% error.     

Calculation of watershed flow concentration based on the grid drop concept

The grid drop concept is introduced and used to develop a micromechanism-based methodology for calculating watershed flow concentration. The flow path and distance traveled by a grid drop to the outlet of the watershed are obtained using a digital elevation model （DEM）. Regarding the slope as an uneven carpet through which the grid drop passes, a formula for overland flow velocity differing from Manning＇s formula for stream flow as welt as Darcy＇s formula for pore flow is proposed. Compared with the commonly used unit hydrograph and isochronal methods, this new methodology has outstanding advantages in that it considers the influences of the slope velocity field and the heterogeneity of spatial distribution of rainfall on the flow concentration process, and includes only one parameter that needs to be calibrated. This method can also be effectively applied to the prediction of hydrologic processes in un-gauged basins.     

Analysis of Runoff Aggregation Structures with Different Flow Direction Methods under the Framework of Power Law Distribution

The main purpose of this study is to evaluate the performances of different flow direction methods (FDM) in affecting the runoff aggregation structures within a watershed under the framework of power law distribution. To this end, SFD (single flow direction method), MFD (multiple flow direction method) and IFD (Infinite flow direction method) were applied for determination of flow direction for water particles in Susu river basin, and consequently assessed with respect to the variation of flow accumulation. The results indicate that different patterns of flow accumulation were observed from each flow direction method. Effect of flow dispersion on DEM is strongest with ascending order of SFD, IFD, MFD. However, contribution of individual pixels into outlet follows descending order of SFD, IFD, MFD. Notably MFD and IFD tend to make additional hydrologic abstraction from rainfall excess due to the flow dispersion within the flow paths generated on DEM. This study also investigated the size distribution of flow accumulation which is equivalent to the drainage area generated from the selected FDM. They were fitted to the power law distribution and flow accumulation was recognized as a scale invariance factor based on the parameter estimation for power law distribution by maximum likelihood. It was also noticed that FDM affects the parameter estimation of power distribution where highest exponent was estimated for MFD following by IFD and SFD.     

基于规则格网DEM的水系提取算法研究

对DEM提取水系算法,尤其是DEM中洼地和平地的识别和处理、平地水流方向的确定等算法进行了讨论,对于几个基于DEM水系提取算法的实现步骤的分解以及适用性进行了分析。在特定的数据质量情况下,算法研究的结果只能来源于原有数据,而不能超过这个限制去获取信息之外的信息;基于DEM提取水系,尤其是在现有算法所需地貌信息不充分的情况下,还要引入尽可能多的真实地貌信息才能取得比较好的效果。     

基于栅格数字高程模型DEM的河网提取及实现

从数字高程模型(DigitalElevationModels)DEM直接提取河网及相关流域信息,是分布式水文模型开发与应用的基础。本文基于D8(eightflowdirectionmatrix)处理方法,开发出一套DEM凹陷区域识别与处理、河网自动生成与流域划分软件。在新疆天山,应用本软件在100m×100m精度的DEM数据上生成的河网与全国1 25万的数字河流对比验证,吻合较好。此外,在美国联邦地质调查局(USGS)的HYDRO1k全球1km精度的DEM数据源基础上,所提取生成的长江流域河网,与1 100万的数字长江主要河道对比,差别不大。结果表明,所开发软件能够很好地自动生成流域水系,可为进一步开发分布式水文模型提供技术基础。     

河网提取算法中河道断裂现象原因剖析及算法改进

Burn-in算法和AGREE算法是目前应用广泛的基于实际河网高程强迫修正的河网提取算法.该算法能有效提取出同真实河网高拟合度的模拟河网,但某些情况下,所提取的河网会产生“断裂”现象.河网“断裂”现象的产生在于实际河网栅格高程“高估”和“低估”所引起的局部流向计算错误,其中所有“低估”类以及大部分“高估”类影响都是可以通过填洼等方法加以消除的,即不会产生“断裂”问题.真正产生“断裂”的原因是：存在“高估”类河网栅格且“高估”所带来的影响无法通过填洼等操作加以消除.基于此,对Burn-in算法和AGREE算法进行修正,提出一种消除“高估”类影响的解决方案,从根本上解决河网“断裂”问题,实现程序自动化处理.渭河流域实例应用表明,改进算法可有效解决模拟河网“断裂”问题,且适用于多种基于高程的强迫修正算法.     

ArcGis 9.0中基于DEM的水文信息提取方法

文中详细介绍了ArcGis 9.0中的水文分析工具箱的使用方法,包括从原始DEM数据提取河网的步骤、应注意的问题,DEM数据的快速裁剪,不同精度DEM数据拼接的方法和技巧.