Why do people not learn from flood disasters? Evidence from Vietnam’s northwestern mountains

This article explores how the causes and impacts of a flood event as perceived by local people shape immediate responses and future mitigation efforts in mountainous northwest Vietnam. Local flood perception is contrasted with scientific perspectives to determine whether a singular flood event will trigger adjustments in mitigation strategies in an otherwise rarely flood-affected area. We present findings from interdisciplinary research drawing on both socioeconomic and biophysical data. Evidence suggests that individual farmers?? willingness to engage in flood mitigation is curbed by the common perception that flooding is caused by the interplay of a bundle of external factors, with climatic factors and water management failures being the most prominent ones. Most farmers did not link the severity of flooding to existing land use systems, thus underlining the lack of a sense of personal responsibility among farmers for flood mitigation measures. We conclude that local governments cannot depend on there being a sufficient degree of intrinsic motivation among farmers to make them implement soil conservation techniques to mitigate future flooding. Policy makers will need to design measures to raise farmers?? awareness of the complex interplay between land use and hydrology and to enhance collective action in soil conservation by providing appropriate incentives and implementing coherent long-term strategies.     

Watershed urbanization and changing flood behavior across the Los Angeles metropolitan region

This article examines the effects of watershed urbanization on stream flood behavior in the Los Angeles metropolitan region. Stream gauge data, spatially distributed rainfall data, land use/land cover, and census population data were used to quantify change in flood behavior and urbanization in multiple watersheds. Increase in flood discharge started at the very early stage of the urbanization when the population density was relatively low but the rate of increase of flood discharge varied across watersheds depending on the distribution of the imperviousness surface and flood mitigation practices. This spatial variability in rainfall–runoff indices and the increasing flood risk across the metropolitan region has posed a challenge to the conventional flood emergency management, which usually responds to flood damages rather than being concerned with the broader issues of land use, land cover, and planning. This study pointed out that alternative land use planning and flood management practices could be mitigating the urban flood implemented hazard.     

太湖流域应对特大洪水防洪工程效益模拟

防洪效益评估对防洪工程投资决策与减灾对策制定具有重要意义。建立集成了与太湖流域防洪效益评估相关的系列模型和方法,包括含降雨产流与平原净雨计算的水文分析方法、由河网水动力学模型和平原区域洪水分析模型组成的大尺度水力学模型、综合流域社会经济和淹没因素的洪灾损失评估模型。模拟了太湖流域遇特大洪水的灾害损失,开展了不同防洪工程应对流域性特大洪水减灾效益的预测分析。结果表明：1999年型200年一遇降雨将会给太湖流域造成高达568.29亿元的直接经济损失,外排动力增强30%至100%的防洪效益介于26.69亿元到45.70亿元之间,新建圩区、太浦河拓宽的防洪效益依次减小,而圩区泵排能力增加30%的防洪效益仅为0.65亿元。基于研究成果提出了增设外排泵站、加强圩区科学调度、通过保险分担风险等应对特大洪水的对策措施建议,为太湖流域特大洪水的防治提供支撑和参考。     

太湖流域应对特大洪水防洪工程效益模拟

防洪效益评估对防洪工程投资决策与减灾对策制定具有重要意义。建立集成了与太湖流域防洪效益评估相关的系列模型和方法,包括含降雨产流与平原净雨计算的水文分析方法、由河网水动力学模型和平原区域洪水分析模型组成的大尺度水力学模型、综合流域社会经济和淹没因素的洪灾损失评估模型。模拟了太湖流域遇特大洪水的灾害损失,开展了不同防洪工程应对流域性特大洪水减灾效益的预测分析。结果表明:1999年型200年一遇降雨将会给太湖流域造成高达568.29亿元的直接经济损失,外排动力增强30%至100%的防洪效益介于26.69亿元到45.70亿元之间,新建圩区、太浦河拓宽的防洪效益依次减小,而圩区泵排能力增加30%的防洪效益仅为0.65亿元。基于研究成果提出了增设外排泵站、加强圩区科学调度、通过保险分担风险等应对特大洪水的对策措施建议,为太湖流域特大洪水的防治提供支撑和参考。     

General framework and key issues concerning integrated strategies for coping with drought and flood in China in a changing environment

This paper focused on the development of a framework for collective water resources management in China to meet the change of drought and flood. Based on the observational data of drought and flood from 1950 to 2009 and the precipitation from 1961 to 2010, using the Standardized Precipitation Index (SPI) method, the evolutionary characteristic of drought and flood was analyzed. The results showed that drought and flood occurred frequently, simultaneous occurrences of drought and flood and the rapid shift between the two were increasing. The framework for collective strategies responding to drought and flood under this ever-changing environment was presented. A series of potential mitigation, prevention, and adaptation strategies were discussed. These included both planning and implementation side strategies. In regard to planning, the strategies for dealing with drought and flood should be shifted from crisis management to collective management, unifying normal and emergency management. Combination risk zoning of drought and flood should be conducted and collective emergency planning should be formulated. Moreover, the regulation capability of water conservancy projects group should be optimized to the highest possible level. In regard to implementation, based on the water resources collective management, rational water allocation for both normal and extreme value processes should be implemented. The water conservancy project groups for the extreme value process should work together, and the flood limit water level of reservoirs should be controlled dynamically.     

Risk perception and hazard mitigation in the Yangtze River Delta region,China

The Yangtze River Delta region is an area highly vulnerable to flooding. As the population density is rising concomitantly with high economic growth, this region is becoming more vulnerable to natural hazards. We conducted a survey to investigate the individual risk perception of both the local authorities and the general community, analyze the current situation regarding risk management and identify problems in the current risk management scheme. Data were collected through questionnaires distributed to some members of the community and interviews with representatives of the local authorities. The primary findings are as follows: (1) risk and disaster multipliers perceived by lay people show the stigma effect of the Wenchuan earthquake; (2) the responses of college students illustrate that the stigma effect has less influence on people who have more knowledge about hazards; (3) differences exist in comparative groups (China and USA), which shows that the society and culture influence people’s perception of risk; and (4) economic activities have complicated flood risk management such as land shortage, ground subsidence and flood diversion. Accordingly, the following measures should be taken: (1) the government should improve the risk communication and education of lay people; (2) the government must also control unsuitable land use and balance economic development and risk management; (3) flood diversion areas should be compensated through special funds collected from other cities; and (4) local governments should provide more support for hazard mitigation.     

Natural hazards in Central Java Province,Indonesia: an overview

Central Java Province, Indonesia, suffers from natural hazard processes such as land subsidence, coastal inundation, flood, volcanic eruption, earthquake, tsunami, and landslide. The occurrence of each kind of natural hazard is varied according to the intensity of geo-processes. It is necessary to learn from the historical record of coastal inundation, flood, volcanic eruption, earthquake, tsunami, and landslide hazards in Central Java Province to address issues of comprehensive hazard mitigation and management action. Through the understanding about the nature and spatial distribution of natural hazards, treatments can be done to reduce the risks. This paper presents the natural hazard phenomena in Central Java Province and provides critical information for hazard mitigation and reduction.     

蓄滞洪区利用与减灾研究

考察了蓄滞洪区管理的复杂性,分析了分洪对蓄滞洪区土地利用的制约作用,讨论了洪灾损失影响因素及估算方法。提出了蓄滞洪区减灾研究的框架和基本内容。介绍了一个应用水文模型、水力学模型和优化模型进行土地利用和减灾研究的实例。     

The ecological effects of structural flood mitigation works on fish habitats and fish communities in the lower Clarence River system of South-Eastern Australia

The effects of flood mitigation structures on the quality of estuarine and freshwater fish habitats in the lower Clarence River system of south-eastern Australia were investigated. Surrounding land use, fringing vegetation, overall level of habitat disturbance, distance from the sea, salinity, and water temperature were examined and compared between four sites on natural tributary streams, four sites on channelized flood mitigation drains gated at their mouths, and ten paired sites (five below and five above floodgates) on flood mitigation drains in this system, from mid 1988 to late 1990. Quantitative sampling of the fish fauna at each of these sites was conducted quarterly over this 21/2-yr period. Juvenile fishes were sampled using netting enclosures together with application of the ichthyocide rotenone, while subadults and adults were sampled using multiple-panel gill nets. In general, fish habitats in the flood mitigation drains, and especially those above flood gates, had more intensive surrounding land uses, less natural native fringing vegetation and, overall, were more highly disturbed than those in the natural tributaries. Salinity at the various study sites was largely dependent on the pattern of seasonal (mainly summer and autumn) rainfall and distance upstream from the sea. Salinities usually differed only slightly between gated and ungated sites at similar distances from the sea, indicating that the floodgates were generally ineffective in preventing the penetration of saline river water into the drains immediately above them. These gates were, however, very effective in preventing the establishment of fringing mangrove vegetation in the drains above them. The main ecological effects of these flood mitigation works have thus been to generally degrade the overall quality of available fish habitat, particularly in terms of reductions in natural fringing vegetation (mangroves in the more estuarine-dominated areas and overhanging terrestrial trees in the more freshwater-dominated areas often being replaced by grassess and rushes), and to increase the intensity of surrounding land use (natural forest often being cleared and wetlands drained for cattle grazing and sugarcane growing), both of these factors contributing to increases in generalized aquatic habitat disturbance. Results from the study of the fish assemblages in these natural and man-altered habitats revealed the following general patterns. Highest fish species numbers and abundances occurred in the ungated natural tributaries and in drains downstream of floodgates. These habitats also contained the largest proportions of both commercial fish species and individuals as well as the majority of species and individuals with marine-estuarine affinities. Both total and commercial fish species numbers generally declined with decreasing salinity and increasing distance of the sampling sites from the sea. Even through saline waters from the main river system penetrated the majority of the floodgates during most of the study period, fish passage through these gates was found to be very restricted. Fish assemblages above such gates were generally dominated by primarily freshwater species, as compared with primarily saltwater (estuarine-marine) species below. The conversion of the great majority of small mangrove-fringed tributaries in the lower reaches of this river system into uniform floodgated drainage channels has thus resulted in the destruction of, and impeded fish access to, large areas of previously available estuarine fish nursery and feeding habitat. These drainage changels are now dominated by terrestrial-freshwater vegetation above where they are cut off from the main river channels by the floodgates, and the period of their construction has coincided with that of reported declines in fish catches in this river system. On the basis of the above findings, it is recommended that these floodgates be left fully open at all times except immediately prior to and during floods in the river system, thus facilitating the re-establishment of fringing mangrove vegetation along the banks of the artificial drains in the lower reaches, generally improving flushing and thus water quality in these drains, and allowing the establishment of primarily estuarine-marine fish communities, including more species of economic importance, in them.     

城市山洪灾害易损性的RS和GIS分析

以受山洪灾害影响突出的云南文山城区为研究区,从承灾体属性特征和社会承灾能力二个方面探讨了城市山洪灾害易损性分析的方法;利用高分辨率遥感卫星影像为数据源完成城市土地覆盖类型解译,在此基础上应用GIS定量分析城市山洪灾害易损性。对承灾体属性特征定量分析结果表明,文山城区50年一遇山洪淹没范围内的承灾体中城市房屋建筑的易损性最大。对易损性要素中的社会承灾能力分析认为,由于文山城区段防洪河道行洪能力低,蓄滞洪能力弱。山洪灾害的易损性仍然较高,山洪对文山城威胁形势严峻。     

Flood prediction and mitigation in coastal tourism areas,a case study: Hurghada,Egypt

Flood mitigation involves the management and control of floodwater movement, such as redirecting flood runoff through the use of floodwalls and flood gates, rather than trying to prevent floods altogether. The prevention and mitigation of flooding can be studied on three levels: on individual properties, small communities, and whole towns or cities. The current study area is located in Hurghada on the Red Sea, which is considered an important area for coastal tourism. The study area is located at distance 7.50 km from El Gouna city along the Red Sea and east of Hurghada–Al Ismaileya road. The aim of this research is to derive the runoff flow paths across the study area and their flow magnitudes under different rainfall events of 10, 25, 50, and 100 year return periods in order to design the flood mitigation measures to protect such important areas. Field data (e.g., topographic data and rainfall intensities) were collected for the study area. The results indicated that the site is exposed to high flash flood risk and protection work is required. In order to protect the area from flood risks, locations of number of drainage channels and dams were selected and designed based on flood quantity and direction. The proposed mitigation system is capable of protecting this crucial area from flood risks and increases the national income from tourism. This study can be applied in different areas of Egypt and the world.     

洪水管理经济评价研究进展

洪水管理经济评价是践行洪水管理治水方略必不可少的环节。从洪水管理经济评价理论、洪灾损失评估以及洪水管理成本效益评估等方面综述了洪水管理经济评价的主要研究进展,分析了目前研究存在的不足,指出现有的防洪经济理论与方法已难以满足洪水管理决策对经济评价的要求。强调建立完善的洪水管理经济评价理论体系,扩展评价内容和范围,深入开展非工程措施效益、生态环境影响和社会公平等评价方法的研究是中国今后洪水管理经济评价研究的重点。     

Flood risk mapping and crop-water loss modeling using water footprint analysis in agricultural watershed,northern Iran

Natural Hazards - Spatial information on flood risk and flood-related crop losses is important in flood mitigation and risk management in agricultural watersheds. In this study, loss of water bound...     

三峡为中心的长江防洪系统实时优化调度模型研究

主要介绍以三峡为中心的长江防洪系统联合调度运行的数学模型--洪水模拟模型和水库优化调度模型.前者包括水文学洪水演进模型,一维非恒定流模型,一维和二维组合洪水模拟模型,荆江分洪区与洪湖分洪区联合运用模型,用于反映洪水在河湖中的运动及防洪措施蓄泄效果;后者由总体控制模型与模糊决策,大系统解耦以及网络分析等模型组成,用于确定使库群起到最佳防洪效果的优化调度策略.     

中国蓄滞洪区洪水管理与可持续发展途径

蓄滞洪区的行蓄洪启用频率和蓄水方式决定着洪水管理与可持续发展途径,影响流域经济社会的可持续发展.根据各大流域蓄滞洪区的设计启用频率,设置了未来35年内蓄滞洪区发展的3种情景:维持现状、部分水库化和部分湿地化,构建了涵盖防洪、社会经济和生态发展等因子的途径选择指标体系,运用数据包络分析法(DEA),识别了不同设计启用频率的蓄滞洪区洪水管理与可持续发展的最优途径.结果表明:① 不同设计启用频率的蓄滞洪区在建成35年内,部分湿地化情景是中国70%蓄滞洪区的最优发展途径.② 设计启用频率50年一遇是蓄滞洪区发展途径选择的边界值;当等于或低于50年一遇时,部分湿地化是其最优途径;当高于50年一遇时,维持其现状是最优途径.     

黄河内蒙古河段河道冲淤演变与凌情响应机制

黄河上游内蒙古冲积性河道凌汛问题突出,研究河道冲淤演变与凌情响应机制可为该河段防凌减灾提供技术支持。根据内蒙古河段凌情、河道冲淤演变资料,分析凌情变化表征指标及与之密切相关的河道冲淤演变特征指标,研究河道冲淤演变特征指标与凌情变化表征指标的响应关系。结果表明:河道冲淤演变的特征指标平滩流量与凌情表征指标冰下过流能力、槽蓄水增量关系密切,冰下过流能力为平滩流量的1/5左右,随着平滩流量减小而减小,而槽蓄水增量随着平滩流量的减小而增大,有利内蒙古河段防凌的平滩流量宜不小于2 000 m3/s,槽蓄水增量宜不超过14亿m3。本研究成果可为内蒙古河段冰凌灾害防治提供参考。     

Hydraulic and flood-loss modeling of levee,floodplain, and river management strategies,Middle Mississippi River,USA

In this investigation, four scenarios were used to quantify the balance between the benefits of levees for flood protection and their potential to increase flood risk using Hazards U.S. Multi-Hazard flood-loss software and hydraulic modeling of the Middle Mississippi River (MMR). The goals of this study were (1) to quantify the flood exposure under different flood-control configurations and (2) to assess the relative contributions of various engineered structures and flood-loss strategies to potential flood losses. Removing all the flood-control structures along the MMR, without buyouts or other mitigation, reduced the average flood stages between 2.3 m (100-year flood) and 2.5 m (500-year), but increased the potential flood losses by $4.3–6.7 billion. Removing the agricultural levees downstream of St. Louis decreased the flood stages through the metro region by ~1.0 m for the 100- and 500-year events; flood losses, without buyouts or other mitigation, were increased by $4.3–6.7 billion. Removing the agricultural levees downstream of St. Louis decreased the flood stages through the metro region by ~1.0 m for the 100- and 500-year events; flood losses, without buyouts or other mitigation, were increased by 155 million for the 100-year flood, but were decreased by $109 million for the 500-year flood. Thus, agricultural levees along the MMR protect against small- to medium-size floods (up to the ~100-year flood level) but cause more damage than they prevent during large floods such as the 500-year flood. Buyout costs for the all the buildings within the 500-year floodplain downstream of urban flood-control structures near St. Louis are ~40% less than the cost of repairing the buildings damaged by the 500-year flood. This suggests large-scale buyouts could be the most cost-effective option for flood loss mitigation for properties currently protected by agricultural levees.     

Hydrological impacts of land use–land cover change and detention basins on urban flood hazard: a case study of Poisar River basin,Mumbai, India

Flooding in urban area is a major natural hazard causing loss of life and damage to property and infrastructure. The major causes of urban floods include increase in precipitation due to climate change effect, drastic change in land use–land cover (LULC) and related hydrological impacts. In this study, the change in LULC between the years 1966 and 2009 is estimated from the toposheets and satellite images for the catchment of Poisar River in Mumbai, India. The delineated catchment area of the Poisar River is 20.19 km². For the study area, there is an increase in built-up area from 16.64 to 44.08% and reduction in open space from 43.09 to 7.38% with reference to total catchment area between the years 1966 and 2009. For the flood assessment, an integrated approach of Hydrological Engineering Centre-Hydrological Modeling System (HEC-HMS), HEC-GeoHMS and HEC-River analysis system (HEC-RAS) with HEC-GeoRAS has been used. These models are integrated with geographic information system (GIS) and remote sensing data to develop a regional model for the estimation of flood plain extent and flood hazard analysis. The impact of LULC change and effects of detention ponds on surface runoff as well as flood plain extent for different return periods have been analyzed, and flood plain maps are developed. From the analysis, it is observed that there is an increase in peak discharge from 2.6 to 20.9% for LULC change between the years 1966 and 2009 for the return periods of 200, 100, 50, 25, 10 and 2 years. For the LULC of year 2009, there is a decrease in peak discharge from 10.7% for 2-year return period to 34.5% for 200-year return period due to provision of detention ponds. There is also an increase in flood plain extent from 14.22 to 42.5% for return periods of 10, 25, 50 and 100 years for LULC change between the year 1966 and year 2009. There is decrease in flood extent from 4.5% for 25-year return period to 7.7% for 100-year return period and decrease in total flood hazard area by 14.9% due to provisions of detention pond for LULC of year 2009. The results indicate that for low return period rainfall events, the hydrological impacts are higher due to geographic characteristics of the region. The provision of detention ponds reduces the peak discharge as well as the extent of the flooded area, flood depth and flood hazard considerably. The flood plain maps and flood hazard maps generated in this study can be used by the Municipal Corporation for flood disaster and mitigation planning. The integration of available software models with GIS and remote sensing proves to be very effective for flood disaster and mitigation management planning and measures.     

长江洪水资源化思考

长江水患是我国最大的自然灾害, 华北缺水是我国最重要的资源环境问题.长江洪水资源化是使二者能够得到统筹解决而提出的一种思路.洪水资源化就是实现由灾害水向资源水和环境水的转化.长江洪水资源化不仅是由长江水资源特点、流域水旱交替频率加大及不断增加的水资源需求所决定, 也是解决华北水资源短缺的重要途径.蓄洪是洪水资源化的基础, 应在完善流域水库网络体系的基础上, 考虑人工控湖工程, 特别要重视蓄洪区建设, 通过“给水让地”, 实现“以土地换和平”和洪水资源化; 可通过引洪冲湖, 治理流域污染湖泊; 南水北调应以调洪水为主, 可通过蓄洪调水和直接引洪北调来实现.