Urban Sprawl in Wadi Goss Watershed (Jeddah City/Western Saudi Arabia) and Its Impact on Vulnerability and Flood Hazards

Today, climate change imposes enormous challenges on a global scale. The interactions of the balances between the need for development, population growth, massive urbanization generate a negative impact on the presence of these climate changes. One of the direct consequences of these changes is the phenomenon of flash floods, a phenomenon that hit the city of Jeddah (city located in west of Saudi Arabia) twice, one in 2009 and the other in 2011, causing significant human and material damage. Floods are considered as a direct result of the combination of extreme weather and hydrological phenomena;in most cases, the magnitude of these floods is magnified by anthropogenic factors, which increases the risk. According to the risk triangle, risk is defined as a probabilistic function that depends on three essential elements: exposure, vulnerability and hazard. If any of these three elements undergo growth the risk also does so and vice versa. Exposure and vulnerability will depend on the presence of human activities in the study area. This study is conducted on the Wadi Goss watershed as it was one of the most violent basins during the 2009 and 2011 floods. Indeed, we present in this study the extent of the urban extension in the Wadi Goss watershed, since 1984 to days and this by the using Landsat images. Given the nature of the study area, we present a method based on the calculation of various indices followed by a classification operation in order to define the urbanized zones inside the Wadi Goss watershed and then estimate the urban sprawl inside the watershed. We also present in this paper, the characteristics of the watershed as well as the evolution of the urbanized areas exposed to the phenomenon of floods and their contribution to the changes of the hydrological behavior of the basin, and to increase the evolution of the risk of the floods. We have shown through this study that the urban footprint has increased from 90 hectares in 1985 to 850 hectares in 2015. This urban footprint represents 12% of the total area of the watershed. Most of the urban evolution was operated on the wadi area with a concentration in the western part of the basin and especially at its outlet.

Use of GIS and Remote Sensing Technology as a Decision Support Tool in Flood Disaster Management: The Case of Southeast Louisiana, USA

The primary objective of this paper was to identify flood-prone areas in Southeast of Louisiana to help decision-makers to develop appropriate adaptation strategies and flood prediction, and mitigation of the effects on the community. In doing so, the paper uses satellite remote sensing and Geographic Information System (GIS) data for this purpose. Elevation data was obtained from the National Elevation Dataset (NED) produced by the United States Geological Survey (USGS) seamless data warehouse. Satellite data was also acquired from USGS Earth explorer website. Topographical information on runoff characteristics such as slope, aspect and the digital elevation model was generated. Grid interpolation TIN (triangulated irregular network) was carried from the digital elevation model (DEM) to create slope map. Image Drape was performed using ERDAS IMAGINE Virtual GIS. The output image was then draped over the NED elevation data for visualization purposes with vertical exaggeration of 16 feet. Results of the study revealed that majority of the study area lies in low-lying and very low-lying terrain below sea level. Policy recommendation in the form of the need to design and build a comprehensive Regional Information Systems (RIS) in the form of periodic inventorying, monitoring and evaluation with full support of the governments was made for the study area.

Techniques of Remote Sensing and GIS as Tools for Visualizing Impact of Climate Change-Induced Flood in the Southern African Region

Flooding is a major problem facing Southern African region. The region has been experiencing flood for the past two decades. This flood event has been exacerbated in recent years by global weather pattern known as La Ni?a which cools ocean waters in the equatorial Pacific and changes rainfall patterns across the world. This change in weather pattern has resulted in increased rainfall over Southern Africa causing flash floods resulting in extensive socioeconomic loses, casualties and environmental damage. This study employs remote sensing and geographical information systems (GIS) data to visualize the impact of climate change caused by flooding in the Southern African region in order to assist decision makers’ plans for future occurrences. To achieve these objectives, the study used Digital Elevation Model (DEM), temporal Landsat Enhanced Thematic Mapper Plus (ETM+) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellites data obtained from the United States Geological Survey (USGS) and NASA’s Earth Observatory websites in order to show the spatial dimensions of the damage and the flooded area. Results of the study revealed notable damages to social and natural environments as well as flood risk zones and watercourses in the study area. The paper concludes by outlining policy recommendations in the form of the need for building drainage ditches on the flat plains identified in this study to accommodate flood flows, the design of a comprehensive Regional Emergency Information System (REIS) with support from the governments in the study area and the neighboring countries. Building such system, the paper concludes could offer decision-makers access to the appropriate spatio-temporal data for monitoring climate change induced emergencies related to seasonal floods.

Implementation of Remote Sensing and GIS Techniques to Study the Flash Flood Risk at NEOM Mega-City, Saudi Arabia

Southern Red Sea flooding is common. Assessing flood-prone development risks helps decrease life and property threats. It tries to improve flood awareness and advocate property owner steps to lessen risk. DEMs and topography data were analyzed by RS and GIS. Fifth-through seventh-order rivers were studied. Morphometric analysis assessed the area’s flash flood danger. NEOM has 14 catchments. We determined each catchment’s area, perimeter, maximum length, total stream length, minimum and maximum elevations. It also uses remote sensing. It classifies Landsat 8 photos for land use and cover maps. Image categorization involves high-quality Landsat satellite images and secondary data, plus user experience and knowledge. This study used the wetness index, elevation, slope, stream power index, topographic roughness index, normalized difference vegetation index, sediment transport index, stream order, flow accumulation, and geological formation. Analytic hierarchy considered all earlier criteria (AHP). The geometric consistency index GCI (0.15) and the consistency ratio CR (4.3%) are calculated. The study showed five degrees of flooding risk for Wadi Zawhi and four for Wadi Surr, from very high to very low. 9.16% of Wadi Surr is vulnerable to very high flooding, 50% to high flooding, 40% to low flooding, and 0.3% to very low flooding. Wadi Zawhi’s flood risk is 0.23% high, moderate, low, or extremely low. They’re in Wadi Surr and Wadi Zawhi. Flood mapping helps prepare for emergencies. Flood-prone areas should prioritize resilience.

Floodplain Mapping and Risks Assessment of the Orashi River Using Re­mote Sensing and GIS in the Niger Delta Region, Nigeria

Residents along the shoreline of the Orashi River have yearly been dis­placed and recorded loss of lives,farmland,and infrastructures.The Gov­ernment’s approach has been the provision of relief materials to the victims instead of implementing adequate control measures.This research employs Shuttle Radar Topographic Mission and Google Earth imagery in devel­oping a 3D floodplain map using ArcGIS software.The result indicates the drainage system in the study area is dendritic with catchment of 79 subbasins and 76 pour point implying the area is floodplain.Incorporating the 3D slope which reveals that>8 and<8 makes up 1.15%and 98.85%of the study area respectively confirms the area is a floodplain.Aspect indicate west-facing slope are dark blue,3D hillshade indicate yellow is very low area and the high area is pink and also the buffer analysis result reveals wa­terbodies reflecting blue with an estimated area of 1.88 km2,yellow indicate 0.79 km2 of the shoreline,red indicate 0.81 km2 of the minor floodplain and pink contain 0.82 km2 with the length of 32.82 km.The result from google earth image in 2007 indicate absent of settlement,2013 indicate minimal settlement and 2020 indicate major settlement in the study area when cor­related with 3D Floodplain mapping before and during the flood in other to analyze and manage flooding for further purpose and the majority of the area are under seize with flood like in 2020.Therefore,Remote Sensing and GIS techniques are useful for Floodplain mapping,risk analysis for control measures for better flood management.

Hazard assessment of landslide disaster using information value method and analytical hierarchy process in highly tectonic Chamba region in bosom of Himalaya

The present study is focused on a comparative evaluation of landslide disaster using analytical hierarchy process and information value method for hazard assessment in highly tectonic Chamba region in bosom of Himalaya. During study, the information about the causative factors was generated and the landslide hazard zonation maps were delineated using Information Value Method(IV) and Analytical Hierarchy Process(AHP) using Arc GIS(ESRI). For this purpose, the study area was selected in a part of Ravi river catchment along one of the landslide prone Chamba to Bharmour road corridor of National Highway(NH^(-1)54 A) in Himachal Pradesh, India. A numeral landslide triggering geoenvironmental factors i.e. slope, aspect, relative relief, soil, curvature, land use and land cover(LULC), lithology, drainage density, and lineament density were selected for landslide hazard mapping based on landslide inventory. Landslide hazard zonation map was categorized namely "very high hazard, high hazard, medium hazard, low hazard, and very low hazard". The results from these two methods were validated using Area Under Curve(AUC) plots. It is found that hazard zonation map prepared using information value method and analytical hierarchy process methods possess the prediction rate of 78.87% and 75.42%, respectively. Hence, landslide hazardzonation map obtained using information value method is proposed to be more useful for the study area. These final hazard zonation maps can be used by various stakeholders like engineers and administrators for proper maintenance and smooth traffic flow between Chamba and Bharmour cities, which is the only route connecting these tourist places.

Remote Sense and GIS-Based Division of Landslide Hazard Degree in Wanzhou District of the Three Gorges Reservoir Area

An evaluation model divided landslide hazard degrees in Wanzhou District of Three Gorges Reservoir Area. The model was established by GIS techniques and took land use/cover, stratum characters, slope aspect, slope gradient, elevation difference and slope shape as evaluation factors. The data of land use/cover were obtained by remote sensing, and the weights of the factors mentioned above were established by the analytic hierarchy process （AHP）. The results indicate, low danger areas in the studied area account for 66.51%, and high danger areas and very high danger areas occupy 1/3 of the total area. The regions of high and very high danger are mainly located around the urban area of Wanzhou District and on the banks of the Yangtze River with a relatively large area, where collapse and landslide directly threats densely populated areas and Three Gorges Reservoir. Slope destabilization, if occurs, will bring huge loss to social economy. All research results are consistent with the actual conditions; therefore, they can be regarded as a useful basis for planning and constructing of the reservoir area.

Life Loss Estimation Based on Dam-Break Flood Uncertainties and Lack of Information in Mountainous Regions of Western China

Compared with urban floods, dam-break floods are associated with greater uncertainties, including variable dam-break modes and hydrological characteristics, so conventional flood estimation methods cannot be directly applied in the estimation of dam-break flood loss. In particular, there is scant information regarding the conditions of affected area and hydrological characteristics in southwest China. In this paper, we introduce an integrated model for estimating flood loss that is adapted to the mountainous regions of southwestern China in light of the relative lack of available information. This model has three major components: a basic information model, a dam-routed flood propagation simulation model, and a loss estimation model. We established the basic information model despite the relative lack of available information using 3S technology [remote sensing (RS); geographical information system (GIS); global positioning system (GPS)], data mining technology, and statistical analysis techniques. Our dam-routed flood propagation simulation model consists of major hydrologic processes and their governing equations for flow propagation, which we solve using finite-difference schemes. In this model, the flood propagation area is divided into grids and each grid is determined by the characteristic parameters obtained from the propagation simulation. We present a case study of the Lianghekou hydropower station in Sichuan Province, China to illustrate the practical application of this integrated model for life loss estimation. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

基于MIKE模型的南沙区内涝模拟研究

基于广州市南沙区2022年的Landsat 8遥感影像数据,通过ENVI 5.3中监督分类方法,解译得到南沙区土地利用数据,通过构建二维地表淹没模型,模拟4种重现期(2年、10年、50年、100年一遇)暴雨条件下,研究区的洪涝淹没与易涝点分布情况。结果表明,该区域土地利用类型以透水区(养殖坑塘、水体、林地与耕地)为主,占研究区总面积的75.41%;当遭遇100年一遇暴雨影响时,会产生4个较为严重的积水区域,最大淹没水深超过1.6 m,易涝区域集中于长距离跨海大桥与沿海人工围垦区域。研究成果可为制定南沙区城市防洪策略提供参考。

基于遥感技术的农村公路勘察设计

研究基于遥感技术的农村公路勘察技术,以国道215线石渠县满真(青川界)至洛须段公路改建工程中的新建里程为研究区域,采用无人机航空摄影遥感技术,获取公路周围的环境勘察遥感图像,同时结合合成孔径干涉雷达(SAR)技术,辨识公路的崩塌、泥石流以及滑坡风险隐患区域,全面完成农村公路勘察,为公路修建提供可靠参考。

Exploitation of Satellite Data for the Mapping of Areas at Risk of Flooding in Grand-Bassam (Côte d’Ivoire)

In order to better identify spatially the areas at risk of flooding for the riparian populations of Grand-Bassam during strong floods, a study aimed at developing hazard and vulnerability maps from RADAR Sentinel-1 and optical images Sentinel-2 has been put in place. The flood hazard study highlighted the flooded areas in Grand-Bassam. These areas represent 747.7 ha, or 1.02% of the total surface. The vulnerability map produced using the maximum likelihood method identified eight (8) land use classes. These are the classes Water, Dense forest, Secondary forest, Swamp forest, Industrial crops, Food crops, Habitats and bare soils. It made it possible to highlight the socio-economic interests of Grand-Bassam. The flood risk map developed from the intersection of the themes of the vulnerability map and that of the hazard has enabled the recognition of risk areas which are located near the source of the risk (Comoé River) and at low altitudes. These are Moossou, Petit Paris, Quartier Phare and Quartier France.

黄河下游藕节形河道游荡趋势演变遥感分析

河道游荡是黄河下游发生自然灾害的主要诱因,分析其游荡规律对保护下游滩区居民的生产生活具有重要意义。针对黄河下游河道游荡问题,本文采用多源国产卫星长时序数列,提出了一种主成分分析-支持向量机(PCA-SVM)黄河河道提取方法,解译了黄河濮阳段2013—2022年的河道信息,并以藕节形河道为例分析了其游荡趋势。结果表明,PCA-SVM方法提取的黄河河道完整,沙洲清晰,显著改善了河道与湿地、滩涂分类混淆等问题,解译精度为84.17%,Kappa系数为0.613,精度明显高于最大似然分类法、最小距离分类法和SVM法。对2013—2022年黄河河道游荡趋势分析可知,研究区内藕节形河道游荡趋势明显,河道主槽已从左岸迁移至右岸,至2022年8月仍存在向右游荡迁移趋势,右岸滩区居民点和农田侵蚀加剧,易引发险工出险,导致洪涝灾害。

暴雨洪涝灾情快速监测评估技术框架体系与应用:以2022年6月北江流域洪水灾情分析为例

【目的】暴雨洪涝灾情快速评估在洪灾应急救援和灾后恢复重建中发挥着重要作用,但仍面临诸多挑战。为快速监测和评估洪涝灾情,建立一套集成天空地网多源信息与多种技术的暴雨洪涝灾情快速监测评估技术框架体系,【方法】以2022年6月北江暴雨洪灾为例,综合利用雨量、河道水位、网络淹没图片和视频、卫星遥感影像、地面调研测绘和无人机低空航测等多源数据、水文模型和地理空间分析技术,通过实地调研测绘和无人机航测,结合遥感影像、水力学模型和地理空间分析技术,快速识别本次洪水淹没深度范围、分析淹没区内的受灾人口、房屋、农田等基本灾情,在洪水灾情分析的实战中检验集成天空地网多源信息的暴雨洪涝灾情快速监测评估技术。【结果】结果显示:清远市新增的淹没面积为478 km^(2),其中淹没农田307 km^(2)(64%),淹没区内有74119栋房屋和167306人;韶关市新增的淹没面积为90 km^(2),其中淹没农田46 km^(2)(51%),淹没区内有15629栋房屋和78037人。【结论】结果表明:无人机航测结合地面RTK高程和洪痕测绘,将在洪涝灾情快速调查评估中发挥越来越重要的作用;卫星影像可快速揭示洪水淹没区的总体格局,但受云层遮档和过境时间的影响,难以获取最大淹没范围;洪涝淹没区公众提供的各类网络众包信息是最直接和现时的洪涝灾情信息,需要认真核实和充分利用;结合河道等各类实测水位,HAND模型可以快速估算出淹没深度范围,有很大的推广应用价值。通过对本次北江洪涝灾情的快速模拟和初步分析,充分展示了各类前沿技术在洪涝灾情快速识别中的独特作用,可为洪涝灾情应急监测方案设计和技术准备提供参考。

3S技术支持下吕梁地区崩塌滑坡地质灾害调查及特征分析

为有效开展崩塌滑坡等灾害的防控工作,将灾害损失降到最小,以3S技术为基础,针对吕梁地区崩塌滑坡地质灾害调查及特征展开分析。探究吕梁地区的地形地貌、气象水文和人类活动等背景信息;利用遥感、地理信息系统和全球定位系统技术,建立地质灾害数据采集与分析系统,针对吕梁地区崩塌和滑坡的演化模式进行分析研究,确定灾害危险区域;计算灾害参数间的拟合程度,分析幂律特征,明确崩塌滑坡和体积之间存在较强的相关性;将灾害点空间分布密度作为指标,划分不同区域的危险程度;分析灾害的时间分布特征,发现该地区的灾害频发时段为汛期。所提方法能够为地质灾害预防和控制工作提供依据,对于减轻灾害损失具有重要意义。

遥感和GIS技术在滑坡地质灾害风险评估中的应用

四川处在青藏高原和四川盆地过渡带,受地形、地貌、地质构造条件和暴雨、地震等诱发因素频发影响,成为全国地质灾害最重的省份之一。本文以其研究区为例,对该区域的地质灾害进行综合评估和分析,采用AHP对研究区进行风险等级评定,并基于GIS技术绘制出风险等级格子图。

基于遥感和GIS的华东区域洪涝灾害动态监测系统的研究和建立

以ＮＯＡＡ卫星资料为主要信息源，以地面高程、土地利用等地形地貌资料为辅助信息源，研制了华 东区域多重因子空间分析模式，在ＧＩＳ平台上建立洪涝灾害动态监测和分析系统，从而提高了洪涝灾害判识 的准确性和客观性．

基于RS与GIS的毕节地区滑坡灾害危险性评价

基于遥感和地理信息系统技术,用空间主成分分析法构建评价指标体系,并用层次分析法确定评价指标权重,以滑坡危害最重的贵州省毕节地区为研究区,选取地层岩性、降水量、土地利用、坡度等9个滑坡孕险因子作为评价指标,对该研究区进行了滑坡灾害危险性评价。通过与研究区的历史滑坡灾害记录结果进行比较发现,评价结果与实际状况较为吻合,说明该方法能较有效地用于对区域滑坡灾害危险性的评价。

地理信息系统/遥感技术支持下三峡库区青干河流域滑坡危险性评价

以统计模型为基础、地理信息系统作为工具的滑坡灾害评价模式已经得到普遍认可和使用,数字高程模型(DEM)、遥感影像、区域地质调查资料已经成为区域滑坡评价研究的因子数据源。选择三峡库区青干河流域顺向坡滑坡多发地段为研究区,在滑坡编目数据库基础上,通过:(1)数字高程模型获取高程、坡度、地形聚水能力因子;(2)遥感影像获取植被指数;(3)区域地质调查资料、数字高程模型计算斜坡类型定量因子TOBIA指数及获取岩石地层单元因子。采用二分类变量逻辑回归评价方法对上述6种因子建立滑坡危险性评价模型,开展地理信息系统/遥感技术支持下顺向坡滑坡危险性评价研究。研究结果表明,根据模型概率值分布和已知滑坡发育关系,可以将研究区划分为高危险区、中等危险区、低危险区3个等级,高危险区包含70%已知滑坡,中等危险区包含14%已知滑坡,评价结果和实际滑坡发育情况吻合,合理地反映区内滑坡灾害发育的总体特征。

基于网格的洪水损失计算模型

首先系统总结了基于GIS和遥感的洪水灾害损失评估框架,并重点阐述了洪水淹没范围的提取和水深的计算;在此基础上,针对洪水灾害损失中的3种主要承灾体(农作物、线状设施以及人员伤亡),提出了基于空间网格的洪水损失计算模型,模型以空间网格为计算单元,以淹没损失曲线为基础;最后,将此模型应用到沱江流域的洪灾损失评估中,得到了较好的结果.

RS和GIS技术在县级区域泥石流危险区划中的应用研究--以四川省泸定县为例

泥石流危险度评价是泥石流灾害预测预报和减灾防灾工作中的重要内容和决策基础。以泸定县为例,利用RS、G IS技术,以流域范围为评价单元,选取影响泥石流发育和形成的因子,采用数理统计方法和层次分析法得出各因子对泥石流的敏感系数和权重,最后建立县级区域泥石流危险度多因子综合评价模型,从而实现区域泥石流危险度评价。