基于PGIS的社区洪涝灾害概率风险评估——以福建省泰宁县城区为例

以福建泰宁县城区为例,基于PGIS 和概率（情景）风险分析方法,开展社区尺度的洪涝灾害风险研究。利用1949-2011年13 次历史洪灾资料,计算了洪水的强度-超越概率,得出大于洪峰流量2929.18 m³/s 和洪峰水位281.50 m的年超越概率为1.6%。在此情景下,县城淹没面积达1.3 km²（占总面积31.0%）,最大淹没深度超过3.5 m,最长淹没时间超过10小时,共有1846 幢建筑物（占全部建筑的42.2%）受影响。分别针对受灾区域房屋建筑、住宅室内财产和商户室内财产,建立灾损方程,评估损失价值,并绘制灾损地图。结果表明,洪涝灾害对社区造成的影响显著,有必要制定应急预案,建立早期预警等进行防灾降险。     

Using LiDAR-DEM based rapid flood inundation modelling framework to map floodplain inundation extent and depth

Mapping floods is important for policy makers to make timely decisions in regards to emergency responses and future planning. It is therefore crucial to develop a rapid inundation modelling framework to map flood inundation. This study develops an airborne scanning laser altimetry(Li DAR) digital elevation model(DEM) based Rapid flood Inundation Modelling framework(Li DAR-RIM) for assessment of inundation extent, depth, volume and duration for flood events. The modelling framework has been applied to the mid-Murrumbidgee region in the southeast Murray-Darling Basin, Australia for two flood events occurred in December 2010 and March 2012. The inundation extents estimated using this methodology compared well to those obtained from two Landsat ETM+ images, demonstrating suitability and applicability of this method. For testing possibility of larger area application, the framework also uses 30-m resolution shuttle radar topography mission(SRTM)-DEM to replace Li DAR-DEM for the same modelling. The inundation extents obtained by using the SRTM-DEM are smaller than those obtained using the Li DAR-DEM, especially for large flood events. A possible reason is that the river cross sections obtained from the SRTM-DEM are not accurate enough for inundation modelling. The Li DAR-RIM has an advantage for process modelling and scenario modelling under future climatic conditions.     

基于PGIS的社区洪涝灾害概率风险评估简

以福建泰宁县城区为例,基于PGIS 和概率（情景）风险分析方法,开展社区尺度的洪涝灾害风险研究。利用1949-2011年13 次历史洪灾资料,计算了洪水的强度—超越概率,得出大于洪峰流量2929.18 m³/s 和洪峰水位281.50 m的年超越概率为1.6%。在此情景下,县城淹没面积达1.3 km²（占总面积31.0%）,最大淹没深度超过3.5 m,最长淹没时间超过10小时,共有1846 幢建筑物（占全部建筑的42.2%）受影响。分别针对受灾区域房屋建筑、住宅室内财产和商户室内财产,建立灾损方程,评估损失价值,并绘制灾损地图。结果表明,洪涝灾害对社区造成的影响显著,有必要制定应急预案,建立早期预警等进行防灾降险。     

Creating and coupling a high-resolution DTM with a 1-D hydraulic model in a GIS for scenario-based assessment of avulsion hazard in a gravel-bed river

In this paper we explore the development and assimilation of a high resolution topographic surface with a one-dimensional hydraulic model for investigation of avulsion hazard potential on a gravel-bed river. A detailed channel and floodplain digital terrain model (DTM) is created to define the geometry parameter required by the 1D hydraulic model HEC-RAS. The ability to extract dense and optimally located cross-sections is presented as a means to optimize HEC-RAS performance. A number of flood scenarios are then run in HEC-RAS to determine the inundation potential of modeled events, the post-processed output of which facilitates calculation of spatially explicit shear stress (τ) and level of geomorphic work (specific stream power per unit bed area, ω) for each of these. Further enhancing this scenario-based approach, the DTM is modified to simulate a large woody debris (LWD) jam and active-channel sediment aggradation to assess impact on innundation, τ, and ω, under previously modeled flow conditions. The high resolution DTM facilitates overlay and evaluation of modeled scenario results in a spatially explicit context containing considerable detail of hydrogeomorphic and other features influencing hydraulics (bars, secondary and scour channels, levees). This offers advantages for: (i) assessing the avulsion hazard potential and spatial distribution of other hydrologic and fluvial geomorphic processes; and (ii) exploration of the potential impacts of specific management strategies on the channel, including river restoration activities.     

基于GIS的复杂地形洪水淹没区计算方法

利用GIS技术计算洪水淹没区范围一直是灾害评估研究中的一个热点问题。通过给出两种情形下基于种子蔓延算法的淹没区计算方法，即有源 淹没和无源淹没。淹没区计算精度主要取决于空间数据精度的优劣；种子蔓延算法及探测分辨率决定了整个模型的效率。文中最后给出了该模型在“水利综合管理信息系统”中得到验证和实现的实例。     

城市暴雨内涝综述：特征、机理、数据与方法

建成环境的高空间异质性与致灾过程的复杂性给城市暴雨内涝研究带来巨大的挑战,具体表现为模型代表性不够、计算效率低、基础数据和验证数据匮乏。以机器学习为代表的人工智能技术、高分遥感和互联网大数据的快速发展则为城市暴雨内涝研究提供了新的契机。论文结合人工智能、高分遥感和互联网大数据等新技术发展,从特征、机理、数据与方法4个维度对暴雨内涝的研究现状和发展趋势进行了系统总结,主要结论包括：① 暴雨内涝具有短历时性、空间散布性、连锁性和突变性,其热点呈现空间上的动态迁移特征。② 降雨时空特征和城市化程度决定暴雨内涝灾害的量级,地形条件尤其是微地形则决定发生位置和内涝频率。地形控制作用指数(topographic control index, TCI)对暴雨内涝发生位置具有良好的指示能力。③ 排水管网、高精度地形和不透水面分布是暴雨内涝模拟的关键基础数据;降雨过程的高时空变异性是暴雨内涝近实时预报预警的主要瓶颈,需要充分利用天气雷达观测提高其精准度;互联网众包大数据是获取高空间覆盖度暴雨内涝灾情信息的新途径,但也面临不同类型信息融合、提炼和质量控制的挑战。④ 结合水动力模拟与机器学习可建立兼具物理基础和计算效率的暴雨内涝模拟方法,是实现近实时模拟与快速预报预警的有效途径。     

Embedding user-generated content into oblique airborne photogrammetry-based 3D city model

Oblique airborne photogrammetry-based three-dimensional (3D) city model (OAP3D) provides a spatially continuous representation of urban landscapes that encompasses buildings, road networks, trees, bushes, water bodies, and topographic features. OAP3D is usually present in the form of a group of unclassified triangular meshes under a multi-resolution data structure. Modifying such a non-separable landscape constitutes a daunting task because manual mesh editing is normally required. In this paper, we present a systematic approach for easily embedding user-generated content into OAP3D. We reduce the complexity of OAP3D modification from a 3D mesh operation to a two-dimensional (2D) raster operation through the following workflow: (1) A region of interest (ROI) is selected to cover the area that is intended to be modified for accommodating user-defined content. (2) Spatial interpolation using a set of manually controlled elevation samples is employed to generate a user-defined digital surface model (DSM), which is used to reform the ROI surface. (3) User-generated objects, for example, artistically painted road textures, procedurally generated water effects, and manually created 3D building models, are overlaid onto the reformed ROI.     

海平面上升背景下黄浦江极端风暴洪水危险性分析

黄浦江流域是典型的风暴洪水脆弱区。随着气候变化和海平面上升,未来该区域可能遭受更为严重的灾害影响。从海平面绝对上升、构造沉降和压实沉降三个方面预测了2030 年和2050 年该区域海平面相对上升值为170 mm和390 mm。在此基础上,结合最大天文潮位值和最大风暴增水值,估算了2030 年和2050 年极端风暴洪水位将分别达到7.17 m和7.39 m。基于高精度洪水数值模型开展了2030 和2050 年两种极端风暴洪水情景模拟,结果显示黄浦江两岸地区均可能被淹没,上游地区较中下游地区受淹将更为严重。进而提出未来研究中需重点关注不确定性分析、防汛墙溃堤淹没情景分析和风暴频率—强度变化等领域。     

Uncertain seas: probabilistic modeling of future coastal flood zones

ABSTRACT

Future sea-level rise will likely expand the inland extent of storm surge inundation and, in turn, increase the vulnerability of the people, properties and economies of coastal communities. Modeling future storm surge inundation enhanced by sea-level rise uses numerous data sources with inherent uncertainties. There is uncertainty in (1) hydrodynamic storm surge models, (2) future sea-level rise projections, and (3) topographic digital elevation models representing the height of the coastal land surface. This study implemented a Monte Carlo approach to incorporate the uncertainties of these data sources and model the future 1% flood zone extent in the Tottenville neighborhood of New York City (NYC) in a probabilistic, geographical information science (GIS) framework. Generated spatiotemporal statistical products indicate a range of possible future flood zone extents that results from the uncertainties of the data sources and from the terrain itself. Small changes in the modeled land and water heights within the estimated uncertainties of the data sources results in larger uncertainty in the future flood zone extent in low-lying areas with smaller terrain slope. An interactive web map, UncertainSeas.com, visualizes these statistical products and can inform coastal management policies to reduce the vulnerability of Tottenville, NYC to future coastal inundation.     

基于洪涝情景模拟的城市公共服务灾害应急响应空间可达性评价——以医疗急救为例

在气候变化和城市化背景下,日益频发的洪涝灾害业已成为当前中国城市面临的重大挑战,也是城市灾害管理和应急响应研究的热点问题之一。本文旨在构建一套适用于城市尺度的洪涝灾害应急响应能力评估范式,以上海市外环以内中心城区为研究区,采用洪涝数值模拟与GIS网络分析相结合的研究方法,评估了当前以及未来正常条件和不同重现期洪涝情景下,城市关键公共服务部门（120急救）应急响应的空间可达性。结果显示：洪涝淹没强度（范围和水深）、道路交通状况（车流速度）以及应急服务机构的数量和位置共同决定了城市洪涝灾害医疗急救的服务范围及响应时间;由于上海市中心城区洪涝影响范围主要分布在黄浦江两岸2~3 km以内区域,因此洪涝对整个中心城区应急医疗服务的影响有限,主要是位于滨江地区部分医院的应急响应范围较正常状态下明显减少,120急救车辆无法或延迟达到部分救援点。研究表明基于洪涝情景模拟的城市公共服务应急响应空间可达性定量化评估方法,具有重要的科学价值和实践意义,可为中国城市洪涝灾害应急管理提供决策依据。     

复杂地形任意天气情形下太阳直接辐射量模拟

以太阳辐射传输参数化模型为基础,结合MODIS影像两次白天的云产品和水汽产品及DEM,构建了复杂地形任意天气情形下每日太阳直接辐射量模型。选取代表不同气候类型与地形起伏状况的3个典型站点（拉萨、北京、额济纳旗）,以2007年每日实测值对模拟结果进行了验证,其相关系数分别为0.77、0.77和0.85。研究表明:有云天气下,云是影响地表太阳直接辐射数量和空间分布的主要因子;模型对时间步长不敏感。引起误差的原因主要是MODIS云产品的时空分辨率较低以及云的3D效应导致模拟的困难,对地形起伏较大地区,小比例尺的DEM也会导致较大的误差,同时实测值与模拟值的空间尺度不匹配也引起了一定误差。     

Determination of three-dimensional velocity structure from observations of refracted body waves

Summary. The computational effectiveness of travel-time inversion methods depends on the parameterization of a 3-D velocity structure. We divide a region of interest into a few layers and represent the perturbation of wave slowness in each layer by a series of Chebyshev polynomials. Then a relatively complex velocity structure can be dcscribed by a small set of parameters that can be accurately evaluated by a linearized inversion of travel-time residuals. This method has been applied to artificial and real data at small epicentral distances and in the teleseismic distance range. The corresponding matrix equations were solved using singular value decomposition. The results suggest that the method combines resolution with computational convenience.     

A GIS-based method for flooded area calculation and damage evaluation

1 IntroductionFlooding simulation and damage evaluation has attracted attention in environmental disaster research fields for many years. Since the 1990s, especially in recent years, using geographic information systems (GIS) technology and its powerful functions of spatial analysis and visualization to simulate and display flooded area and to evaluate disaster damage has become a research hotspot. Most of the papers involved in this field are from hydraulic and hydrologic point of view and b…     

Exploring the sensitivity of coastal inundation modelling to DEM vertical error

As sea level is projected to rise throughout the twenty-first century due to climate change, there is a need to ensure that sea level rise (SLR) models accurately and defensibly represent future flood inundation levels to allow for effective coastal zone management. Digital elevation models (DEMs) are integral to SLR modelling, but are subject to error, including in their vertical resolution. Error in DEMs leads to uncertainty in the output of SLR inundation models, which if not considered, may result in poor coastal management decisions. However, DEM error is not usually described in detail by DEM suppliers; commonly only the RMSE is reported. This research explores the impact of stated vertical error in delineating zones of inundation in two locations along the Devon, United Kingdom, coastline (Exe and Otter Estuaries). We explore the consequences of needing to make assumptions about the distribution of error in the absence of detailed error data using a 1 m, publically available composite DEM with a maximum RMSE of 0.15 m, typical of recent LiDAR-derived DEMs. We compare uncertainty using two methods (i) the NOAA inundation uncertainty mapping method which assumes a normal distribution of error and (ii) a hydrologically correct bathtub method where the DEM is uniformly perturbed between the upper and lower bounds of a 95% linear error in 500 Monte Carlo Simulations (HBM+MCS). The NOAA method produced a broader zone of uncertainty (an increase of 134.9% on the HBM+MCS method), which is particularly evident in the flatter topography of the upper estuaries. The HBM+MCS method generates a narrower band of uncertainty for these flatter areas, but very similar extents where shorelines are steeper. The differences in inundation extents produced by the methods relate to a number of underpinning assumptions, and particularly, how the stated RMSE is interpreted and used to represent error in a practical sense. Unlike the NOAA method, the HBM+MCS model is computationally intensive, depending on the areas under consideration and the number of iterations. We therefore used the HBM+ MCS method to derive a regression relationship between elevation and inundation probability for the Exe Estuary. We then apply this to the adjacent Otter Estuary and show that it can defensibly reproduce zones of inundation uncertainty, avoiding the computationally intensive step of the HBM+MCS. The equation-derived zone of uncertainty was 112.1% larger than the HBM+MCS method, compared to the NOAA method which produced an uncertain area 423.9% larger. Each approach has advantages and disadvantages and requires value judgements to be made. Their use underscores the need for transparency in assumptions and communications of outputs. We urge DEM publishers to move beyond provision of a generalised RMSE and provide more detailed estimates of spatial error and complete metadata, including locations of ground control points and associated land cover.     

GIS技术支持下的洪水模型建模

在复杂区域建立洪水模型时,计算网格的手工生成方法容易出错甚至不可行,自动生成算法则可大大节省计算网格生成的工作量。洪水模型中的计算网格与GIS栅格数据及不规则三角网空间数据结构非常相似,因此,GIS中成熟的网格自动生成算法可用于生成洪水模型计算网格。文章详细讨论了GIS支持下的洪水模型自动建立步骤,并以黄河下游花园口～夹河滩河段为例,利用地形图、土地利用图、水利工程设施分布、水文站点图等资料,通过自动生成网格及其空间拓扑关系,建立了洪水过程数值模拟模型,并详细解释了计算网格数据格式。     

Modelling Spatial Patterns of Overbank Sedimentation on Embanked Floodplains

This paper presents a GIS-based mathematical model for the simulation of floodplain sedimentation. The model comprises two components: (1) the existing hydrodynamic WAQUA model that calculates two-dimensional water flow patterns; and (2) the SEDIFLUX model that calculates deposition of sediment based on a simple mass balance concept with a limited number of model parameters. The models were applied to simulate floodplain sediment deposition over river reaches of several kilometres in length. The SEDIFLUX model has been calibrated and validated using interpolated raster maps of sediment deposition observed after the large magnitude December 1993 flood on the embanked floodplain of the lower river Rhine in the Netherlands. The model appeared to be an adequate tool to predict patterns of sediment deposition as the product of the complex interaction among river discharge and sediment concentration, floodplain topography, and the resulting water flow patterns during various discharge levels. In the investigated areas, the resulting annual average sedimentation rates varied between 0.5 mm/year and 4.0 mm/year. The role of the most important mechanisms governing the spatial patterns of overbank deposition, i.e. inundation frequency, sediment load, floodplain topography and its influence on the flow patterns over the floodplain, are discussed.     

A LiDAR-based flood modelling approach for mapping rice cultivation areas in Apalit,Pampanga

Majority of rice cultivation areas in the Philippines are susceptible to excessive flooding owing to intense rainfall events. The study introduces the use of fine scale flood inundation modelling to map cultivation areas in Apalit, a rice-producing municipality located in the province of Pampanga in the Philippines. The study used a LiDAR-based digital elevation model (DEM), river discharge and rainfall data to generate flood inundation maps using LISFLOOD-FP. By applying spatial analysis, rice cultivation zone maps were derived and four cultivation zones are proposed. In areas where both depth and duration exceed threshold values set in this study, varieties tolerant to stagnant flooding and submergence are highly recommended in Zone 1, where flood conditions are least favorable for any existing traditional lowland irrigation varieties. The study emphasizes that a decline in yield is likely as increasing flood extents and longer submergence periods may cause cultivation areas for traditional irrigated lowland varieties to decrease over time. This decrease in yield may be prevented by using varieties most suitable to the flooding conditions as prescribed in the rice zone classification. The method introduced in this study could facilitate appropriate rice cultivation in flood-prone areas.     

城市天空开阔度矢量/栅格估算方法对比

城市天空开阔度（Sky View Factor,SVF）是重要的城市形态学参数,为了找出高效可靠的方法定量分析城市天空开阔度,对比了矢量与栅格两种估算方法在城市天空开阔度估算与制图中的表现。以福建省晋江市为例,选取了软件计算法中的矢量计算法和栅格计算法对天空开阔度进行估算,并在结果的宏观分布规律、不同方法结果数值差异、不同分辨率结果一致性几方面进行对比分析。结果表明：与栅格估算法相比,矢量估算方法估算结果与城市建筑结构相符合,估算结果数据分布规律更合理,不同分辨率结果一致性更高,在较高的分辨率下更适应城市天空开阔度定量分析与制图的需要;但在低分辨率情况下,两种方法直接计算结果的代表性都极低。     

洪涝灾害遥感监测研究

本文讨论了利用陆地卫星、气象卫星和航空侧视雷达等遥感技术进行洪涝灾情监测的技术方法,并应用于1991年江淮地区特大洪涝灾害的快速调查与分析。