基于RS和GIS的大南川水库溃坝灾害模拟方法研究

综合运用遥感图像处理系统和地理信息系统,探讨一种无需编程即可快速计算水库溃坝后所产生的洪水量、下游淹没水深和淹没面积的溃坝模拟方法,适用于溃坝源头与淹没区落差较大地区。以青海大南川水库灌溉区的南川河流域作为研究区域,假定由于暴雨、地震等自然灾害的发生使得大南川水库坝体瞬间溃决而形成有源洪水,计算洪水到达时间、淹没区的洪水深度和淹没面积,并分析洪水造成的损失情况,通过模拟计算,其结果比较接近实际。     

洪水淹没分析中的自适应逐点水位修正算法

洪涝灾害损失评估是防洪减灾科学决策的基础,其中洪水淹没分析是准确提取洪水淹没范围、水深及历时等灾情信息的关键。洪水淹没分析主要采用数字高程模型数据,由于DEM的格网分辨率与高程精度有限,常出现异常的洼地或平地,导致难以可靠地计算每个格网点处的流向,而传统方法采用统一高程的洼地填平处理又使得容易出现洪水演进过程中复杂起伏地形水面爬坡以及平坦地形水位断流的问题,为此提出顾及流速和淹没时间的自适应逐点水位修正算法,即在DEM坡面流模拟的基础上,根据洪水水流特性、地形、边界变化、水流速度、水深变化以及淹没点的淹没时间,计算水位修正值,对洪水演进过程中每个格网点的水位进行修正,采用多种地貌类型的DEM数据进行试验,证明洪水演进的淹没范围、水深及历时的实时计算结果准确可靠,可为快速评估灾害损失与防洪决策服务提供更为科学的依据。     

基于GIS与RS的中小流域洪水风险图研究

以苏鲁皖三省交界处的复新河流域为研究区,在多源数据集成与融合的基础上,利用GIS与RS技术分析了流域地形地貌,提取了水文模型参数,集成了洪水模拟,从而进行洪水淹没与影响分析,并对洪水模拟结果进行自动可视化处理与发布。系统地阐述了运用GIS与RS技术快速制作中小流域洪水风险图的关键技术,并构建了洪水风险可视化模型,可实现快速一体化成图,提高中小流域洪水风险图的动态适应性。     

水淹没模型在水库规划建设中的应用

利用DEM生成等高线模拟静态水平面的方法，模拟水库和地震造成的堰塞湖水淹没模型，叠置二维和三维地理信息数据进行GIS综合分析，用于分析评估淹没损失、预测淹没区域及应急指挥调度。     

基于GIS的洪水淹没损失研究

以江苏省东山镇为例,对利用GIS技术估算洪水淹没损失的方法进行了研究,提出了以1：10000地形图数字化数据作为建立DEM的原始数据,对不同区域按不同等高距内插加密提高DEM精确度,通过Supermap栅格计算功能计算洪水淹没范围和淹没深度,并根据居民经验和调查、统计所得的损失率估算洪水淹没损失的方法。     

采用滞留水量的洪水淹没计算

针对城市地区暴雨致洪问题以及快速、科学分析处理洪涝灾害的应急测绘保障服务工作要求,该文提出了一种基于滞留水量的洪水淹没计算分析方法。采用美国水土保持局提出的模型计算降雨产水量,结合区域排水能力,河网、湖泊、水库调蓄水能力和境外来水量,实现区域滞留水量计算分析;在此基础上,利用数字高程模型数据和洪水淹没分析方法,实现区域淹没水深和淹没范围计算分析。研究区实例计算验证结果表明:该方法能够满足应急测绘保障服务工作要求,快速为相关部门洪涝灾害分析提供科学决策依据。     

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.     

基于哨兵数据相干性的洪水淹没范围确定方法

洪涝灾害会造成农田淹没、居民住宅损毁等危害,因此对洪水淹没范围进行实时、准确监测可有效进行灾后治理。利用光学传感器提取洪水淹没范围时,不能穿透云层,因此无法获取有效地面信息;而SAR使用微波波段,不受天气影响,在夜间也能成像。因此,SAR成为洪水灾害灾情评估的有力工具。本文利用2021年9月23日、10月5日、10月17日3景SAR雷达影像Sentinel-1A数据,计算相干性系数,设置阈值为0.2,提取水体淹没范围,分析其扩张范围及变化趋势,并根据生成的形变图分析水位抬升变化,验证了基于雷达数据的相干系数阈值提取方法监测洪水淹没范围,以及采用InSAR技术准确提取水体边界与分析水位上升趋势的可行性。     

基于ArcGIS的洪水淹没分析模拟及可视化

基于数字高程模型(DEM)格网模型,通过改进迭代种子蔓延算法,实现给定水深情况下洪水淹没区的讣算模型,讨论洪水淹没演进过程可视化实现的关键技术,并使用ArcEngine开发包进行二次开发,以二维和二三维两种可视化方式,动态而形象地模拟在指定洪水水位下的洪水淹没演进过程.试验证明,所提出的实现方法切实有效,便于推广应用,为快速、准确及科学地进行洪灾评估洪水风险图的制作提供良好的基础,对洪涝灾害进行评估和预测分析具有重要意义.     

时序Sentinel-1A数据支持的长江中下游汛情动态监测

合成孔径雷达（SAR）因其对地观测全天候、全天时优势,成为多云多雨天气限制下洪水动态监测中不可或缺的数据来源之一。由于GEE（Google Earth Engine）云计算平台的兴起和短重访Sentinel-1数据的可获取性,洪水监测与灾害评估目前正面向动态化、广域化快速发展。顾及洪水淹没区土地覆盖变化的复杂性和发生时间的不确定性,基于时序Sentinel-1A卫星数据提出了针对大尺度范围、连续长期的汛情自动检测及动态监测方法。该方法首先,利用图像二值化分割时序SAR数据实现水体时空分布粗制图,逐像素计算时间序列中被识别为水体候选点的频率。然后,利用Sentinel-2光学影像对精度较粗的初期SAR水体提取结果进行校正,得到精细的水体分布图。最后,针对不同频率区间的淹没特点,采用差异化的时序异常检测策略识别淹没范围：对低频覆水区利用欧氏距离检测时序断点,以提取扰动强度大、淹没时间短的洪涝灾害区;对高频覆水区利用标准分数（Z-Score）检测时序断点,以提取季节性水体覆盖区。在GEE平台上利用该方法,实现了2020-05—10长江中下游地区全域洪水淹没范围时空信息的自动、快速、有效监测,揭示了不同区域汛情发展模式的差异性。本文提出的洪水快速监测方法对大尺度下的汛情动态监测、灾害定量评估和快速预警响应具有重要的现实意义。     

无/缺水下地形数据的高原堰塞湖水量遥感估算

水量遥感动态监测对于高原堰塞湖风险评估、预报预警和处置决策等具有重要意义。针对高原无资料或缺资料区,充分利用空天遥感技术,文章提出了一种无/缺水下地形数据的高原堰塞湖水量遥感定量估算方法。该方法首先通过遥感水域面积提取,获取堰塞湖淹没空间范围;进而采用不规则复杂多边形中线定位算法,确定堰塞湖中心线位置;然后基于河道中心特定点高程信息,结合局部河道比降估算,生成堰塞湖水下地形河道中线约束因子;再根据河道边坡高程信息和水下地形约束因子自适应拟合出局部堰塞河道的水下未知地形;最后通过三维曲面离散积分实现堰塞湖水量遥感动态定量估算。实验以东帕米尔高原的萨雷兹堰塞湖为研究区,展开遥感水量调查与局部验证研究,结果表明:萨雷兹堰塞湖当前水域面积约为89.09 km²,水量约为162.49亿m³;这一结果与专家预估的水资源量155—165亿m³基本吻合。经局部模拟实验精度对比验证,模拟结果与实际数据动态误差总体控制在10%以内,相关系数达到0.95(P<0.01,双尾),进一步证明了算法的鲁棒性和估算结果的可信度。为无/缺水下地形数据的高原堰塞湖水量遥感估算提供了一种有效的方法,实现了水下地形未知的高原堰塞湖水量遥感快速反演与定量测算。     

Updated Inventory of Glacial Lakes in Teesta Basin Using Remote Sensing Data for Use in GLOF Risk Assessment

Detailed inventory of glacial lakes in a Glacial Lake Outburst Flood (GLOF) prone area is vital for disaster mitigation. Availability of cheaper high resolution satellite data from Indian remote sensing satellites enables us to create up-to-date inventory for use in prioritisation of glacial lakes for GLOF risk assessment. Earlier inventories show presence of more glacial lakes in Brahmaputra basin in Indian Himalaya. Teesta River is one of the tributary of Brahmaputra and previous studies have shown that the inventory of glacial lakes in Teesta basin varies from 143 to 320. In the present study, the inventory carried out using satellite data of years 2000, 2007 and 2014 show presence of 301 (25.789 km²), 302 (26.081 km²) and 644 (29.706 km²) glacial lakes in Teesta basin respectively. The steep increase in number of lakes in the latest inventory is primarily due to the finer spatial resolution of satellite data used. Analysis of water spread area of glacial lakes at different altitudes shows that most of the lakes in the higher altitudes are small in size. It is observed that more than 66% of lakes are in the altitude beyond 4500 m and of size less than 50,000 sqm (5 ha). Out of 301 glacial lakes inventoried during 2000, water spread area of 6 lakes have decreased in 2014 and 31 lakes have shown increase in area. Out of these 31 lakes, 17 lakes are classified as end moraine dammed lakes and among them, 14 are located in Upper Teesta sub-basin and in higher altitudes (beyond 5000 m). The prioritisation of these lakes for GLOF risk needs to be carried out with detailed field investigation.     

中巴02B卫星数据地质灾害调查典型应用

中巴02B星成功发射以来，已在平原地区的多个领域获得广泛应用。汶川地震后， 02B星获取了自震后第2天-5月13日至6月14日的灾区影像数据。这些卫星数据为各部门的抢险救灾工作提供了现势资料。本文介绍02BCCD数据图像与震前ETM图像结合调查5.12地震极重灾区湔江流域的堵江灾害，共解译了堵江长度为120.6m~2665.8m的54段堵江，并分析了堵江分布与映秀-北川逆冲大断裂的关系。02B卫星图像与其它高分辨率遥感图像配合可进行大型地质灾害解译。     

A geospatial study of the drought impact on surface water reservoirs: study cases from Texas,USA

Satellite images have been used historically to measure and monitor fluctuations in the surface water reservoirs. This study integrates remote sensing and Geographic Information System (GIS) technologies to investigate the impact of drought on 10 selected surface water reservoirs in San Angelo and Dallas, Texas. Oscillations in summer and winter months throughout the 2005–2016 period were assessed using multispectral images from Landsat-5, ?7, and ?8, and changes in the reservoirs were characterized and correlated against local climate data of each reservoir. For quantitative comparisons of the time-series measurements, a robust density slicing approach was employed to classify the range of values of the raster cells in the near-infrared band of Landsat images for each lake into three desired classes (deep water, shallow water, and dry area) based on the natural breaks inherent in the dataset. Statistical analysis shows that the overall accuracy of the classification is about 94%, which demonstrates the efficiency of the density slicer to accurately estimate surface water area changes from an individual Landsat band. Shrinkage in the surface water area over the study period reveals the concrete impact that the drought along with other factors have on the 10 selected lakes. The San Angelo lakes located in west central Texas experienced a nearly consistent pattern of change during most of the study period; whereas the Dallas lakes in northeast Texas followed the oscillating pattern of drought and correlated closely to the local conditions. Shockingly, the extreme drought caused complete vanishing of several lakes, and consequently Texas had to remove them from its recreational plans. Our new findings can certainly help with the water resource management in Texas and our study approach can be adapted for monitoring lake oscillations in other areas across the world. This geospatial study demonstrates the societal benefits from incorporating remote sensing and GIS in investigating geo-environmental problems associated with severe climate changes.     

基于GF-6的可可西里典型湖泊水体面积提取方法研究

湖泊是气候变化的敏感指示器,快速准确地获取湖泊水体信息对区域气候变化研究、区域生态环境保护和治理具有重要意义。本文基于高分六号(GF-6) WFV数据,以可可西里地区4个湖泊为研究对象,分别采用单波段法、波段差值法、归一化差异水体指数(NDWI)法提取了水体面积,并以目视解译所得结果作为参考标准,对不同方法的提取结果进行了精度评价。结果表明,单波段法易受浅水区水体影响,但受积雪的影响较小,而波段差值法和NDWI法受积雪影响较大;NDWI法虽能有效提取浅水区水体,但仍受一定程度湖底沉积物的影响;波段差值法与单波段法和NDWI法相比,能有效区分浅水区水体和背景地物。     

Mapping and characterization of inland wetlands using remote sensing and GIS

Sustainable management of wetland ecosystem is necessary as it serves the important functions such as food storage, water quality maintenance and providing habitat for different species of wildlife. Hence, an inventory of wetlands in any given area is a pre-requisite for their conservation and management. A study has been carried out to delineate the wetlands of east Champaran district of Bihar, India, using IRS ID LISS III data. The data for the pre and post monsoon seasons have been analysed and the wetlands have been qualitatively characterized based on the turbidity and aquatic vegetation status. The extent of water logging problem in the study area was inferred from the seasonal variation of waterspread during both the seasons. The three categories of wetlands (ponds/lakes, water logged areas and oxbow lakes) have been identified. From the analysis, it has been observed that the inland wetlands constitute 2.7% of the study area, of which 1.8% is subjected to water logging. Thus, this study highlights the usefulness of remotely sensed data for wetland mapping, seasonal monitoring and characterization.     

中国湖泊分布与变化：全国尺度遥感监测研究进展与新编目

湖泊提供重要的生产生活用水,在维系生态安全方面发挥显著的价值。中国地理环境复杂多样,湖泊类型各异,不同湖区间的湖泊时空变化特征及驱动机制复杂。两次全国湖泊调查是国家尺度的湖泊变化监测的开创性工作,近年来伴随遥感数据源的海量积累和湖泊遥感提取方法的快速发展,大尺度湖泊水体变化遥感监测研究取得了长足的发展。然而,由于人工判读、湖泊类型判别依据和遥感数据源时相的差异,湖泊水体遥感提取结果及面积估算存在不同程度的出入。首先,本文总结了现有全国尺度湖泊监测研究的遥感数据源、方法和结果,分析了不同研究分析结果差异的可能原因。其次,本文基于1980s—2010s时段Landsat影像制图的湖泊水淹频率数据集的最大水域范围信息,提取并生成了全国湖泊新编目,以其作为该时段内湖泊判定和水体变化监测空间约束的统一参照,避免了因遥感数据时相与年际、年内湖泊水域范围波动对遥感提取结果及湖泊面积计算带来的差异。最后,本文从湖泊水淹范围频度的统计角度,初次提出了可体现湖泊面积年内与年际变化情况的统计指标——概率等效面积,用于监测和指示湖泊水域动态。结果表明,近30年来,中国有3741个最大水域范围大于1 km²的湖泊,总面积约93723 km²,其中青藏高原湖区的湖泊数量约占全国三分之一,总面积超过了全国的一半。全国湖泊总面积呈显著上升趋势,不同湖区的变化趋势差异明显:青藏高原湖区和新疆湖区湖泊面积显著上升,东部平原湖区、内蒙古高原湖区和云贵高原湖区显著下降,东北平原与山地湖区波动式变化、趋势不显著。研究结果总体表明中国湖泊水资源的时空不平衡状况在加剧。     

Classification of glacial lakes using integrated approach of DFPS technique and gradient analysis using Sentinel 2A data

It is important to identify and locate glacial lakes for assessing any potential hazard. This study presents a combination of semi-automatic method Double-Window Flexible Pace Search (DFPS) and edge detection technique to identify glacial lakes using Sentinel 2A satellite data. Initially, Normalized Difference Water Index (NDWI) has been used to identify water and non-water areas, while DFPS and Edge detection technique has been used to identify an optimum threshold value to distinguish between water and shadow areas. The optimal threshold from DFPS process is 0.21, while threshold value of gradient magnitude using edge detection process is 0.318. The number of glacial lakes identified using the above algorithm is in close agreement with previously published results on glacial lakes in Gangotri glacier using different techniques. Thus, a combination of DFPS and edge detection process has successfully segregated glacial lakes from other features present in Gangotri glacier.     

Robust river boundaries extraction of dammed lakes in mountain areas after Wenchuan Earthquake from high resolution SAR images combining local connectivity and ACM

River boundaries extraction from SAR imagery is valuable for flood monitoring and damage assessment. Several rivers, parts of which include dammed lakes caused by landslides and rock avalanches triggered by the 2008 Wenchuan Earthquake, were taken as a case study for robust extraction. In this paper, a novel state-of-the-art approach for automated river boundaries extraction using high resolution synthetic aperture radar (SAR) intensity imagery is presented. The key of our approach lies in the combined usage of local connectivity feature of the river and a region-based active contours model (ACM) in a variational level set framework to differentiate between river and the background. First, sub-patched intensity thresholding segmentation is applied to SAR imagery. Pixels with intensities below the threshold are selected as potential river pixels while the others are potential background pixels. Second, potential river pixels are divided into several connected regions, considering that the river is a big connected region, only relatively bigger regions with similar contrast value are retained as the regions of interest (ROI) while others are noise due to pixel-level decision approach in the first step or shadows due to mountains terrain. Third, the ROI and their contours are regarded as local region and the initial contours to refine the river boundaries, which are used to reduce the scene complexity of ACM and its sensitivity to initial situation, respectively. A novel ACM driven by local image fitting (LIF) energy is presented and used for river boundaries extraction for the first time, which is not only robust against inhomogeneity widely spread in SAR imagery but also can work with efficiency without the need of re-initialization during iteration compared to traditional ACM. The proposed approach was tested on numerous high resolution airborne SAR images containing connected rivers or dammed lakes obtained by Chinese domestic radar system after Wenchuan Earthquake. For the overall dataset, the average commission error, omission error and root mean squared error were 6.5%, 3.3%, and 0.51, respectively. The average computational time for 4000 by 4000 image size was 21 min using a PC-based MATLAB platform. Our experimental results demonstrate that the proposed approach is robust and effective.     

喜马拉雅山地区冰湖信息的遥感自动化提取

在“全域—局部”分步迭代水体信息提取方法的基础上, 通过对水体信息提取指标——水体指数的物理特性的分析实现了算法中全域阈值的自动选择与局部阈值的自适应调整, 并结合DEM 生成的山体坡度和阴影信息,减少局部迭代过程中对其他地表特征与水体信息的误判。在此基础上, 建立一种适合于高山地区冰川湖泊的自动化提取方案。试验采用Landsat 数据对喜马拉雅山地区的冰川湖泊进行信息提取, 结果表明该方法能够快速准确地完 成大区域范围内的冰川湖泊制图, 并能最大程度地消除高山地区湖泊水体识别中冰川和山体阴影的影响。