Flood Maps and Bank Shifting of Dharla River in Bangladesh

Bangladesh is prone to severe flooding as being located at the confluence of three mighty rivers named the Ganges, Brahmaputra, and Meghna. As a consequence, river flooding and erosion are common natural disasters that severely affect the landscape, lives and economy of the country. Dharla River, one of the trans-boundary rivers originated in the Himalayas, along with Brahmaputra River has a great influence on the recurring floods and erosion in north-western Bangladesh. Almost in every year, excessive erosion and embankment damages caused by Dharla render a thousand of people homeless with massive loss of crops and poultries. As per the environmentalists, this is a matter of huge concern as development of accurate flood maps and erosion prediction for Dharla River has been very challenging. In this study, the flood map and Dharla River bank shifting study have been developed by using HEC-RAS 4.1.0 hydrodynamic model and Landsat satellite images. In addition, the HEC-GeoRAS was used to establish the river reach for HEC-RAS. The calibration and validation have been performed using the observed and simulated water levels for the years of 2013 and 2014 respectively. The HEC-RAS flood water level output was used in HEC-GeoRAS for raster interpolation followed by overlain onto the land surface elevation of the study area. Then, the difference between water level interpolation and land elevation surfaces has been considered as a depth of inundation which is performed in Arc-Map 10.2. Flood maps have been generated for the years 2010, 2013, and 2014 for highest water level of each year. The erosion prone areas have been indicated by analyzing bank shifting of Dharla River for the years 1987, 1997, 2007, and 2017 by digitizing the satellite images in Arc-GIS 10.2. From the observation it has been found that the course of the Dharla River has been shifted vastly since 1987 to 2017 due to erosion.

Dam-break Flood Simulation under Various Likely Scenarios and Mapping Using GIS:Case of a Proposed Dam on River Yamuna,India

The precision modeling of dam break floods can lead to formulation of proper emergency action plan to minimize flood impacts within the economic lifetime of the assets.Application of GIS techniques in integration with hydrological modeling for mapping of the flood inundated areas can play a momentous role in further minimizing the risk and likely damages.In the present study,dam break analysis using DAMBRK model was performed under various likely scenarios.Probable Maximum Flood (PMF)calculated for a return period of 1000 years using deterministic approach was adopted for dam break analysis of the proposed dam under various combinations of breach dimensions.The available downstream river cross-sections data sets were used as input in the model to generate the downstream flood profile.Dam break flow depths generated by the DAMBRK model under various combinations of structural failure are subsequently plotted on Digital Elevation Model(DEM)of the downstream of dam site to map the likely affected area.The simulation results reveals that in one particular case the flood without dam may be more intense if a rainfall of significant intensity takes place.

Integration of Remote Sensing Data and GIS Tools for Accurate Mapping of Flooded Area of Kurigram, Bangladesh

Flood is the most devastating disaster in the present world which causes damage to environmental, social, economical and human lives at about 43% of all natural disasters. There are many flood hazard occurs in Bangladesh during the 19th century and 20th century in the different regions. These flood hazards have more catastrophic damages of huge area within human lives and other necessary properties of Bangladesh. The first step of flood management is to evaluate the area which is under threat of flood disaster. In this study here showed the importance of Remote Sensing (RS) data and Geographic Information System (GIS) tools to manage the flood related problems. Remote Sensing (RS) data and Geographic Information System (GIS) provide a lot of information to flood disaster management. ArcView GIS software tools are used for digitizing the base map and to create a flood risk zone of Kurigram, Bangladesh where images of remote sensing can be helped to determine the flood inundation areas. The integrated application of RS and GIS techniques for monitoring and flood mapping provides information for the decision makers. The study also grows attentions the need of cost-efficient methodology by creating a flood vulnerable map of Bangladesh.

Unsupervised GRNN flood mapping approach combined with uncertainty analysis using bi-temporal Sentinel-2 MSI imageries

Floods occur frequently worldwide.The timely,accurate mapping of the flooded areas is an important task.Therefore,an unsupervised approach is proposed for automated flooded area mapping from bitemporal Sentinel-2 multispectral images in this paper.First,spatial–spectral features of the images before and after the flood are extracted to construct the change magnitude image(CMI).Then,the certain flood pixels and non-flood pixels are obtained by performing uncertainty analysis on the CMI,which are considered reliable classification samples.Next,Generalized Regression Neural Network(GRNN)is used as the core classifier to generate the initial flood map.Finally,an easy-toimplement two-stage post-processing is proposed to reduce the mapping error of the initial flood map,and generate the final flood map.Different from other methods based on machine learning,GRNN is used as the classifier,but the proposed approach is automated and unsupervised because it uses samples automatically generated in uncertainty analysis for model training.Results of comparative experiments in the three sub-regions of the Poyang Lake Basin demonstrate the effectiveness and superiority of the proposed approach.Moreover,its superiority in dealing with uncertain pixels is further proven by comparing the classification accuracy of different methods on uncertain pixels.

Development of a Web-Based GIS of Flood Zones in the Municipality of Ouagadougou in Burkina Faso

This document describes the creation of an informative Web GIS aimed at mitigating the impacts of flooding in the municipality of Ouagadougou, in Burkina Faso, a region that is highly sensitive to climate change. Burkina Faso, which is undergoing rapid urbanization, faces major natural threats, particularly flooding, as demonstrated by the severe floods of 2009 that caused loss of life, injury, structural damage and economic losses in Ouagadougou. The aim of this research is to develop a web map highlighting the municipality’s flood-prone areas, with a view to informing and raising awareness of flood risk reduction. Using the Leaflet JavaScript mapping library, the study uses HTML, CSS and JavaScript to implement web mapping technology. Data on Ouagadougou’s flood zones is generated by a multi-criteria analysis combining Saaty’s AHP method and GIS in QGIS, integrating seven (7) parameters including hydrography, altitude, slope, rainfall, soil types, land use and soil moisture index. QGIS processes and maps the themes, PostgreSQL with PostGIS serves as the DBMS and GeoServer functions as the map server. The Web GIS platform allows users to visualize the different flood risks, from very low to very high, or the high-risk areas specific to Ouagadougou. The AHP calculations classify the municipality into five flood vulnerability zones: very low (24.48%), low (27.93%), medium (23.01%), high (17.11%) and very high (7.47%). Effective risk management requires communication and awareness-raising. This online mapping application serves as a tool for communication, management and flood prevention in Ouagadougou, helping to mitigate flood-related natural disasters.

Flash flood hazard mapping: A pilot case study in Xiapu River Basin, China

Flash flood hazard mapping is a supporting component of non-structural measures for flash flood prevention. Pilot case studies are necessary to develop more practicable methods for the technical support systems of flash flood hazard mapping. In this study, the headwater catchment of the Xiapu River Basin in central China was selected as a pilot study area for flash flood hazard mapping. A conceptual distributed hydrological model was developed for flood calculation based on the framework of the Xinanjiang model, which is widely used in humid and semi-humid regions in China. The developed model employs the geomorphological unit hydrograph method, which is extremely valuable when simulating the overland flow process in ungauged catchments, as compared with the original Xinanjiang model. The model was tested in the pilot study area, and the results agree with the measured data on the whole. After calibration and validation, the model is shown to be a useful tool for flash flood calculation. A practicable method for flash flood hazard mapping using the calculated peak discharge and digital elevation model data was presented, and three levels of flood hazards were classified. The resulting flash flood hazard maps indicate that the method successfully predicts the spatial distribution of flash flood hazards, and it can meet the current requirements in China.

Modeling and Mapping Flood Hazard with a Flood Risk Assessment Tool: A Case Study of Austin, Texas

As a hazard, flood is an extremely important indicator of how a city is resilient to waterborne diseases and epidemics. Over many decades, flood as a hazard has been a major factor in inducing displacement of marginalized section of the people. Austin city within Central Texas has been identified as one of the major hotspots for flooding in recent decades. Thus, the objectives of the paper are two folded: 1) Empirically, we analyzed and mapped out the susceptibility levels from the factors of physical environments to assess the risk of urban flooding (rainfall data, surface water bodies and topography);in Austin, Texas and 2) Methodologically, we created a re-useable ArcGIS scripting tool that can be used by researchers to automate the process of flood risk modelling with certain criteria. The paper showcases a novel time sensitive building of a tool which will enable better visibility of flood within the city of Austin.

Flood Hazard Mapping of Lower Indus Basin Using Multi-Criteria Analysis

Flooding has been one of the recurring occurred natural disasters that induce detrimental impacts on humans, property and environment. Frequent floods is a severe issue and a complex natural phenomenon in Pakistan with respect to population affected, environmental degradations, and socio-economic and property damages. The Super Flood, which hit Sindh in 2010, has turned out to be a wakeup call and has underlined the overwhelming challenge of natural calamities, as 2010 flood and the preceding flood in 2011 caused a huge loss to life, property and land use. These floods resulted in disruption of power, telecommunication, and water utilities in many districts of Pakistan, including 22 districts of Sindh. These floods call for risk assessment and hazard mapping of Lower Indus Basin flowing in the Sindh Province as such areas were also inundated in 2010 flood, which were not flooded in the past in this manner. This primary focus of this paper is the use of Multi-criteria Evaluation (MCE) methods in integration with the Geographical Information System (GIS) for the analysis of areas prone to flood. This research demonstrated how GIS tools can be used to produce map of flood vulnerable areas using MCE techniques. Slope, Aspect, Curvature, Soil, and Distance from Drainage, Land use, Precipitation, Flow Direction, and Flow Accumulation are taken as the causative factors for flooding in Lower Indus Basin. Analytical Hierarchy Process-AHP was used for the calculation of weights of all these factors. Finally, a flood hazard Map of Lower Indus Basin was generated which delineates the flood prone areas in the Sindh province along Indus River Basin that could be inundated by potential flooding in future. It is aimed that flood hazard mapping and risk assessment using open source geographic information system can serve as a handy tool for the development of land-use strategies so as to decrease the impact from flooding.

Flash Flood Hazard Mapping Using GIS and Bivariate Statistical Method at Wadi Bada’a, Gulf of Suez, Egypt

The area is a part of the Egyptian Eastern Desert in the northwestward to the Gulf of Suez. It covers an area of about 542 square kilometers. Wadi Bada’a is devoid of vegetation, because of the arid climate and water scarcity. However, the present study concerns the flash flood and its impact on the industrial zone and connected road at wadi Bada’a. In this work, the bivariate statistical method using frequency ratio was used to evaluate the areas of potential risk. Geographic Information System package (GIS) was used to analyze and calculate different data sets. The different data source has been used in the research to produce a flood hazard susceptibility map of the area, including the geologic maps, Landsat-8 imagery, land use, and soil type associated with field investigation and data collection. Spatial database with elements at risk, related features and attributes at wadi Bada’a, were constructed. Training data were created randomly in the study area to create an inventory map with testing data. The inventory location of 95 location points has been created. The inventory datasets were divided into 75% of training datasets and 25% testing data. The independent flood-related factors were evaluated by analyzing each independently and assessing their impact on flooding with inventory datasets. The flood susceptibility maps were constructed-using training and testing datasets have been used to evaluate using the success rate method. The results of the accuracy assessment showed a success rate of 76.6% of Area Under Curve. Therefore, the main road in the study area almost at high risk in many parts because of flash flood, additionally the industrial activities located in the moderate risk zone.

Estimation of peak runoff and frequency in an ungauged stream of a forested watershed for flood hazard mapping

Kaynasli District in the western Black Sea region of Turkey has long been vulnerable to frequent flood damage due to the establishment of settlements within and around stream channels without regard to fluctuating peakstreamflow frequencies. The aim of this research was to determine the measures needed to protect the towns and villages from this type of damage. Daily total precipitation data for 1975–2010 were analysed, and rainfall-runoff models developed to estimate the potential yearly maximum discharge from each stream of sub-watersheds dominated by forests and/or agriculture. This was then calculated for different frequencies of the yearly maximum discharge. Flood analysis and mapping was modified via the one-dimensional Hydrologic Engineering CentersRiver Analysis System software to produce potential maximum discharge and geometric data for Kaynasli Creek. As the main creek of the sub-watershed, its crosssection was shown to be insufficient and incapable of containing the maximum discharge at the 100-year frequency presumed for the watershed, and subsequently was seen as having a high level of casualty risk. It was concluded that the one dimensional model could be useful, but 2D models were more suitable for these types of watersheds.

MIKE FLOOD耦合模型在杭嘉湖流域嘉兴地区洪水风险图编制工作中的应用

中国是世界上受洪涝灾害影响最为严重的国家之一,随着社会经济的快速发展,洪灾损失也越来越严重。我国正将防洪策略从洪水控制向洪水管理进行转变。洪水管理需要进行洪水风险分析,数值模拟则是洪水风险分析的一个重要手段。依托全国洪水风险图编制试点项目(二期)工作,以浙江嘉兴地区为研究对象,运用MIKE11软件建立该区域一维河网模型,模拟河道水位变化情况。再运用MIKE 21软件建立该区域二维模型,模拟暴雨情况下的洪水演进过程。最后运用MIKE FLOOD耦合模型,模拟河道溃堤洪水在区域内的演进情况,分析洪水风险,为嘉兴地区洪水风险图编制工作提供技术支撑。

Rainwater harvesting systems: An urban flood risk mitigation measure in arid areas

Rainwater harvesting (RWH) systems have been developed to compensate for shortage in the water supply worldwide. Such systems are not very common in arid areas, particularly in the Gulf Region, due to the scarcity of rainfall and their reduced efficiency in covering water demand and reducing water consumption rates. In spite of this, RWH systems have the potential to reduce urban flood risks, particularly in densely populated areas. This study aimed to assess the potential use of RWH systems as urban flood mitigation measures in arid areas. Their utility in the retention of stormwater runoff and the reduction of water depth and extent were evaluated. The study was conducted in a residential area in Bahrain that experienced waterlogging after heavy rainfall events. The water demand patterns of housing units were analyzed, and the daily water balance for RWH tanks was evaluated. The effect of the implementation of RWH systems on the flood volume was evaluated with a two-dimensional hydrodynamic model. Flood simulations were conducted in several rainfall scenarios with different probabilities of occurrence. The results showed significant reductions in the flood depth and flood extent, but these effects were highly dependent on the rainfall intensity of the event. RWH systems are effective flood mitigation measures, particularly in urban arid regions short of proper stormwater control infrastructure, and they enhance the resilience of the built environment to urban floods.

运用MapXtreme技术进行防汛网络GIS开发

MapXtreme for Windows是MapInfo公司推出的基于Internet的网络地图应用服务器。本文详细介绍了MapXtreme的B/S结构模型,网络GIS的特点和利用MapXtreme进行网络GIS开发的基础、方法,并运用MapXtreme技术进行了防汛网络GIS开发的实践研究,成功实现了某实验地区防汛图形信息的网上发布、检索和分析,建立了该地区防汛GIS网站。

电阻阵列Flood非均匀性测试

在红外成像半实物仿真领域,电阻阵列一直是近20多年的研究热点,但其固有的辐射非均匀性对成像的保真度有着很大的负面影响。为了对电阻阵列进行非均匀性校正,必须对电阻阵列的非均匀性进行精确的测量。给出了电阻阵列Flood非均匀性测试法系统模型;分析了莫尔条纹的产生原因;针对非1:1映射比例下Flood非均匀性测试方法产生的莫尔条纹,提出了基于莫尔条纹预测的电阻阵列Flood非均匀性测试方法。仿真结果表明,该方法在小于1:1映射比例下可以取得很好的效果。

基于Map 3D的洪水演进可视化系统应用研究

根据洪水演进模拟对于可视化的需求,以AutoCAD Map 3D 2011为基础平台,利用Active X/VBA接口编程技术,进行二次开发建立洪水演进可视化系统。采用CAD图元与GIS数据结合显示的方法,在Map 3D中实现了洪水演进的可视化,并针对工程实际需求,在系统中研发实现了淹没区域的点查询、面查询及缓冲区分析等实用功能。

Study and Analysis of Chennai Flood 2015 Using GIS and Multicriteria Technique

Terrain characteristics of the land and meteorological properties of the region are the main natural factors for flood. The recent flood in Chennai was unexpected and not triggered by the above factors. Sometimes floods occur when the watershed size is considerably small which leads to the over flow of water inland may due to the encroachment and the urban development of the city. Temporarily used backwater effects in sewers and local drainage channels and creation of unsanitary conditions may cause flooding. Chennai flood was basically claimed to occur due to improper drainage system and underlying strata which was found to be landfill over the ponds and lakes. The Coouam River which flows through the centre of main city was found silting due to the improper drainage facilities and encroachment by the local peoples who causes flood. For the analysis of potentially affected areas Geographical Information System (GIS) integrated with Multicriteria Decision Analysis (MCDA) were employed. Ranking and displaying the potentially risky areas, the spatial Multicriteria analysis was used. It has been revealed that all most all the area’s having populations are likely to be exposed to flood hazard. At the end of study, a map of flood risk areas was generated and studied with a view to assisting decision makers on the consequences posed by the disaster.

上海城区动态洪水风险图应用系统及典型暴雨内涝分析

【目的】为了提高沿海超大城市对洪涝灾害的先知先觉能力,快速预测分析洪涝潮组合影响下的淹没风险时空分布,【方法】以水文-水动力暴雨洪水分析模型为核心模块,通过与外部的气象精细化降雨预报数据库、自动雨量站实时监测数据库及实时水情、闸泵运行数据库相关联,研发了上海城区动态洪水风险图应用系统。采用由雨量站点到气象格网和水力网格的降雨二级空间融合技术,实现了模型与气象预报降雨数据的有效耦合。利用数据挖掘提取和GIS空间分析技术构建了包含10项洪水风险要素要点的城市内涝预报专报自动生成方法,实现了对内涝风险的快速一站式概览。利用系统可以对城市暴雨、河道洪水和风暴潮等单一发生或遭遇组合引起的淹没分布进行快速实时预报计算,模拟和预测城市洪涝潮灾害的有关淹没特征数据和淹没动态过程。【结果】利用系统分析了2023年6月23—24日暴雨的内涝风险分布,将模型模拟的积水区域与积水监测站、灾情直报和热线灾报的积水点进行对比,结果显示在150处对比积水点中,有129处误差不超过20 cm,占86%。模型模拟的积水空间分布与实际情况基本接近。【结论】结果表明:系统满足汛期常态化、业务化运行需求,能够为城市洪涝风险的实时动态分析和防汛指挥决策提供重要工具。

基于元启发式算法优化的新乡市洪水风险评价

为提高新乡市洪水风险评价模型的评估能力,采用层次分析法(AHP)、逻辑回归(LR)模型、BP神经网络、随机森林(RF)模型以及结合元启发式算法粒子群优化(PSO)的PSO-BP模型和PSO-RF模型6种方法对新乡市进行洪水风险评估,生成包含200个洪水位置的洪水清单图。选择9个洪水影响因子,采用方差膨胀因子分析了洪水影响因子与洪水发生的相关性。利用混淆矩阵和受试者工作特性曲线对比6种洪水风险评估方法的评估能力,最后获得6种方法的洪水风险分布图。结果表明:PSO-RF、PSO-BP模型的评估效果优于单一算法,受试者工作特性曲线下面积分别为0.953、0.947;根据得到的洪水风险分布图,新乡市至少36.5%的地区被列为高度易受洪水影响的地区,耦合元启发式算法后的洪水风险评价模型具有更高精度。

广东省沿海平原中小河流淹没图编制方法初探

广东省沿海平原中小河流具有比降缓、潮汐影响大、淹没范围广和堤围密集等特点,其淹没图编制至今无统一方法。该文通过Mike21和Arcgis软件,结合河流特性,参考《山丘区中小河流洪水淹没图编制技术指引》,以乌坎河为例探求出一种适用于广东省沿海平原中小河流的淹没图编制方法。该方法具有可操作性强、准确性较高和适用范围较广等特点,为后续广东省沿海平原中小河流淹没图制作提供参考。

洪潮影响下潭江流域安全行洪阈值研究

为研究洪潮叠加影响下潭江流域下游感潮河段河道洪水演进动态与行洪能力,构建了一维水动力模型,通过多组洪潮组合工况模拟计算,量化了不同潮位、控制水位、持续泄流时间下潭江流域控制性节点安全行洪阈值以及涨落潮情形下的行洪能力,揭示了洪潮影响下潭江流域水文变化规律,并结合随机森林模型,绘制了高精度安全行洪阈值图谱。结果表明:以潮动力为主的潭江流域下游感潮河段,干流水位主要受下游潮位影响,高潮位的洪潮顶托效应更为强烈,安全行洪阈值受潮位和泄流时间影响;落潮时段行洪能力较涨潮时段明显增强,且落潮时段行洪能力与控制断面水位基本呈线性变化。