首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 296 毫秒
1.
Floods are one of nature's most destructive disasters because of the immense damage to land, buildings, and human fatalities.It is difficult to forecast the areas that are vulnerable to flash flooding due to the dynamic and complex nature of the flash floods.Therefore, earlier identification of flash flood susceptible sites can be performed using advanced machine learning models for managing flood disasters.In this study, we applied and assessed two new hybrid ensemble models, namely Dagging and Random Subspace(RS) coupled with Artificial Neural Network(ANN), Random Forest(RF), and Support Vector Machine(SVM) which are the other three state-of-the-art machine learning models for modelling flood susceptibility maps at the Teesta River basin, the northern region of Bangladesh.The application of these models includes twelve flood influencing factors with 413 current and former flooding points, which were transferred in a GIS environment.The information gain ratio, the multicollinearity diagnostics tests were employed to determine the association between the occurrences and flood influential factors.For the validation and the comparison of these models, for the ability to predict the statistical appraisal measures such as Freidman, Wilcoxon signed-rank, and t-paired tests and Receiver Operating Characteristic Curve(ROC) were employed.The value of the Area Under the Curve(AUC) of ROC was above 0.80 for all models.For flood susceptibility modelling, the Dagging model performs superior, followed by RF,the ANN, the SVM, and the RS, then the several benchmark models.The approach and solution-oriented outcomes outlined in this paper will assist state and local authorities as well as policy makers in reducing flood-related threats and will also assist in the implementation of effective mitigation strategies to mitigate future damage.  相似文献   

2.
Bangladesh has a unique hydro-geological setting and deltaic floodplain which is jointly formed by the deposition of the Ganges (Padma), Brahmaputra (Jamuna) and Meghna River. The physical characteristics of the geographic location, river morphology and the monsoon climate render Bangladesh highly vulnerable to natural disasters, primarily, floods and cyclones. River flooding has exerted a great impact on the culture and socioeconomic activities. The char people and their settlements in the Padma River channel are under threat due to floods and associated river bank erosion. The excess of water happens during the monsoon season because of widespread flooding that damages char-land settlements, agricultural crops, infrastructure and communication networks. Purba Khas Bandarkhola Mouza of Char-Janajat is largely affected by annual floods, and as a result the char people are displaced frequently from one place to another within and/or outside the char. The dwellers can return to the native char when new land emerges in the river channel after floods. This study has revealed that the displacement of char settlement takes place in almost every 3–5a at Purba Khas Bandarkhola Mouza of Char-Janajat. Our findings shed light on the char flood disaster management and social adaptation plan for settlement development of char livelihood in the Padma River basin in the Ganges delta of Bangladesh.  相似文献   

3.
Floods are among the most costly natural disasters interms of human sufferings and economic losses inBangladesh. Approximately 20% of the countryexperiences normal annual flooding while all thehistorical catastrophic floods inundated more thanfifty percent of the country's total area. The recentflood in 1998 has been found to be more severe thanall previous floods. During the flooding season of1998, the Flood Forecasting and Warning Center (FFWC)of the Bangladesh Water Development Board (BWDB)prepared daily flood bulletin and incorporatedinformation about rainfall, rise/fall of riverwater, flood forecasting for 24 and 48 hr inadvance and warning messages (if any). The FFWCattempted to provide adequate services to the localand national level decision-making process. Theforecasting procedure adapted by the FFWC was based onhydrological information, forecaster's experience, andmodel simulation. This paper primarily examines therole and activities of the FFWC, especially in floodforecasting and warning. Identification of the causesand consequences of 1998 flood is the other pertinentarea of discussion of the paper.Findings of this research revealed that the flood of1998 was caused by heavy downpour in the upstream thatwas drained out through the major rivers inBangladesh. Three major rivers' peak was synchronizedand characterized it as the most prolonged flood inthe history of Bangladesh. It also revealed that,despite various limitations, the flood forecasts ofthe FFWC were reasonably adequate to meet nationaldemand during the crises of 1998.  相似文献   

4.
Improving the accuracy of flood prediction and mapping is crucial for reducing damage resulting from flood events. In this study, we proposed and validated three ensemble models based on the Best First Decision Tree (BFT) and the Bagging (Bagging-BFT), Decorate (Bagging-BFT), and Random Subspace (RSS-BFT) ensemble learning techniques for an improved prediction of flood susceptibility in a spatially-explicit manner. A total number of 126 historical flood events from the Nghe An Province (Vietnam) were connected to a set of 10 flood influencing factors (slope, elevation, aspect, curvature, river density, distance from rivers, flow direction, geology, soil, and land use) for generating the training and validation datasets. The models were validated via several performance metrics that demonstrated the capability of all three ensemble models in elucidating the underlying pattern of flood occurrences within the research area and predicting the probability of future flood events. Based on the Area Under the receiver operating characteristic Curve (AUC), the ensemble Decorate-BFT model that achieved an AUC value of 0.989 was identified as the superior model over the RSS-BFT (AUC = 0.982) and Bagging-BFT (AUC = 0.967) models. A comparison between the performance of the models and the models previously reported in the literature confirmed that our ensemble models provided a reliable estimate of flood susceptibilities and their resulting susceptibility maps are trustful for flood early warning systems as well as development of mitigation plans.  相似文献   

5.
This paper examines the nature and causes of September 2004 hazardous flood that affected the dry and drought prone southwestern region of Bangladesh. It also examines human perception of this new hazard and their methods of adjustments to its negative impacts. Field research for this study includes personal interviews of 453 victim families living in four thanas (lowest administrative units) in Jessore and Satkhira districts of southwestern Bangladesh. Findings of the study suggest that all victim respondents viewed this flood event as a natural hazard, which has caused severe damage to standing crops, fish ponds, permanent trees and homesteads, and deteriorated human health and sanitation conditions. Its long-term impacts on fish farming, soil quality degradation, as well as changing land use/land coverage are also noteworthy but yet to be adequately explored. Both perceived and scientific causes of this flood event include high rainfall for a week before the flood, unusual movement of low pressure system into the affected area, cloudy weather and low evaporation, siltation of the regional riverbeds, and rolling back of the Ganges River water through the Ichamati and Bhagirati rivers. These factors also caused hazardous flooding at the same time in the Ichamati and Bhagirati Rivers and their floodplains in the West Bengal province of India. To release the overflow of flood water inside India, the Indian border patrol breached the Ichamati river embankment in several places along Satkhira and Jessore international border which had aggravated the flood situation in the study area.  相似文献   

6.
This paper deals with various types of natural disasters which occur very frequently in Bangladesh. Disaster can occur at any time, in any place, in any dimension, and may owe as much to the circumstances as to the scale of the event. With the exception of the man-made disaster of war, famine, fire, pollution, accident and civil strife, the worst disasters follow natural events.Bangladesh is widely known as a land of natural disasters and is highly vulnerable to flood, cyclone and river erosion. By the effects of these disasters the country is now permanently in distress. These disasters have become a regular phenomenon and cause suffering to millions of people of the country since many decades. Besides, it also focuses on policy options concerning disaster management.  相似文献   

7.
This paper presents the methods and results of visual interpretation of satellite imagery for estimating areal extent of the 1988 flood in Bangladesh. The main limitation of this method was that cloud-free images were not available for the peak flood period in the first week of September. Relatively cloud-free images on three selected dates in the last three weeks of September showed that areas of inundation on those dates ranged from 44000 to 60000 km2 ± 5% (31 to 42% of Bangladesh). The Government of Bangladesh official estimates of the areal extent of flooding were tentative in nature, since these were based on a choropleth map of relative proportions (percentages) of flooding in different parts of the country. The official estimate of the maximum extent of flooding was 82000 km2 (57% of Bangladesh), i.e. 15 to 26% larger than the area shown on satellite imagery. The actual extent of flooding was certainly larger than the estimates from satellite imagery but, perhaps, smaller than the official estimates, since a reduction of 15 to 26% of flood area in one to three weeks seemed unlikely. An alternative method of mapping flood-affected areas by using newspaper-interpreted data was attempted, but the method had limited values because of reporting bias.  相似文献   

8.
Flood is among the deadliest disasters in India, and the frequency of floods and extreme precipitation events is projected to increase under the warming climate. The frequency of floods in India varies geographically as some regions are more prone to floods than the others. The Kerala flood of 2018 caused enormous economic damage, affected millions of people, and resulted in the death of more than 400 people. Here we provide a hydroclimatological perspective on the Kerala flood of 2018. Using the observations and model simulations from the Variable Infiltration Capacity (VIC) model, we show that the 2018 extreme precipitation and runoff conditions that caused flooding were unprecedented in the record of the past 66 years (1951–2017). Our results show that mean monsoon precipitation has significantly declined while air temperature has significantly increased during 1951–2017 in Kerala. The drying and warming trends during the monsoon season resulted in a declined total runoff in large part of the state in the last 66 years. Apart from the mean hydroclimatic conditions, extreme precipitation, and extreme total runoff have also declined from 1951 to 2017. However, 1 and 2-day extreme precipitation and extreme runoff conditions in August 2018 exceeded substantially from the long-term 95th percentiles recorded during 1951–2017. Since there is no increase in mean and extreme precipitation in Kerala over the last six decades, the extreme event during August 2018 is likely to be driven by anomalous atmospheric conditions due to climate variability rather anthropogenic climate warming. The severity of the Kerala flood of 2018 and the damage caused might be affected by several factors including land use/land cover change, antecedent hydrologic conditions, reservoir storage and operations, encroachment of flood plains, and other natural factors. The impacts of key drivers (anthropogenic and natural) on flood severity need to be established to improve our understanding of floods and associated damage.  相似文献   

9.
The Subarnarekha River in east India experiences frequent high magnitude flooding in monsoon season.In this study, we present an in-depth analysis of flood hydrology and GIS-based flood susceptibility mapping of the entire catchment. About 40 years of annual peak discharge data, historical cross-sections of different gauging sites, and 12 flood conditioning factors were considered. Our flood susceptibility mapping followed an expert knowledge-based multi-parametric analytical hierarchy process(AHP) and optimized AHP-VIP methods. Peak hydrology data indicated more than 5 times higher discharge contrasted with the mean streamflow of the peak monsoon month in all hydro-monitoring stations that correspond to possible overbank flooding in the shallow semi-alluvial reaches of the Subarnarekha River. Widthdepth ratio revealed continuous changes on the channel cross-sections at decadal scale in all gauging sites. Predicted flood susceptibility map through optimized AHP-VIP method showed a great amount of areas(38%) have a high probability of flooding and demands earnest attention of administrative bodies.The AHP-VIP based flood susceptibility map was theoritically validated through AUC approach and it showed fairly high accuracy(AUC = 0.93). Our study offers an exceptionally cost and time effective solution to the flooding issues in the Subarnarekha basin.  相似文献   

10.
Bangladesh is a country that comprises much of the world’s largest delta, formed from the Ganges, Brahmaputra, and Meghna (GBM) rivers and their tributaries. Flooding is a fact of life in Bangladesh where up to two-thirds of the country is flooded annually from combined monsoonal rains and Himalayan snowmelt. For this reason, understanding flood dynamics on both local and regional scales is critical. However, flood hazard studies to date typically rely on single flooding events to create flood maps and to evaluate flood hazards using satellite imagery. Here we use geographic information systems to analyze weekly water level data from 304 river gauges and over 1200 groundwater gauges from the Bangladesh Water Development Board to determine the spatial and temporal changes in flood depth and extent. These data cover an eight year period from 2002 to 2010 and provide a temporal resolution that match or are better than that of available satellite imagery. Country-wide ground and surface water levels and corresponding annual flooding events were determined along with groundwater level, flooding, and precipitation trends in Bangladesh at multiple scales. We find that while precipitation within the GBM basin has steadily increased through the time series, the average country-wide inundation depth and absolute water level has been decreasing. These respective trends could be attributed to improved flood management strategies in Bangladesh and surrounding countries that are within the GBM basin, as well as fluctuating weather patterns, declining volume of Himalayan snowmelt runoff, dam construction upriver from the GBD both within and outside the Bangladesh border, and increased groundwater abstraction of shallow groundwater aquifers for sustaining life in the eighth most populous country in the world.  相似文献   

11.
With regard to the lack of quality information and data in watersheds, it is of high importance to present a new method for evaluating flood potential. Shannon’s entropy model is a new model in evaluating dangers and it has not yet been used to evaluate flood potential. Therefore, being a new model in determining flood potential, it requires evaluation and investigation in different regions and this study is going to deal with this issue. For to this purpose, 70 flooding areas were recognized and their distribution map was provided by ArcGIS10.2 software in the study area. Information layers of altitude, slope angle, slope aspect, plan curvature, drainage density, distance from the river, topographic wetness index (TWI), lithology, soil type, and land use were recognized as factors affecting flooding and the mentioned maps were provided and digitized by GIS environment. Then, flood susceptibility forecasting map was provided and model accuracy evaluation was conducted using ROC curve and 30% flooding areas express good precision of the model (73.5%) for the study area.  相似文献   

12.
This study examined the efficacy of three machine ensemble classifiers, namely, random forest, rotation forest and AdaBoost, in assessing flood susceptibility in an arid region of southern Iraq. A dataset was created from flooded and non-flooded areas to train and validate the ensemble classifiers using a binary classification scheme (1—flood, 0—non-flood). The prepared dataset was then partitioned into two sets with a 70/30 ratio: 70% (2478 pixels) for training and 30% (1062 pixels) for testing. A total of 10 influential flood factors were selected and prepared based on data availability and a literature review. The selected factors were surface elevation, slope, plain curvature, topographic wetness index, stream power index, distance to rivers, drainage density, lithology, soil and land use/land cover. The information gain ratio was first utilised to explore the predictive abilities of the factors. The predictive performances of the three ensemble models were compared using six statistical measures: sensitivity, specificity, accuracy, kappa, root mean square error and area under the operating characteristics curve. The results revealed that the AdaBoost classifier was the best in terms of the statistical measures, followed by the random forest and rotation forest models. A flood susceptibility map was prepared based on the result of each classifier and classified into five zones: very low, low, moderate, high and very high. For the model with the best performance, i.e., the AdaBoost model, these zones were distributed over an area of 6002 km2 (44%) for the very low–low zone, 2477 km2 (18%) for the moderate zone and 5048 km2 (40%) for the high–very high zones. This study proved the high capabilities of ensemble machine learning classifiers to decipher flood susceptibility zones in an arid region.  相似文献   

13.
通过研究现代洪水沉积特征,可重建洪水水文过程,识别泥沙侵蚀源区,既可为防洪水利工程设计提供依据,也可为古洪水层判识建立参考.2018年8月中旬,山东省北部弥河、 丹河流域受双台风影响发生洪涝灾害.通过对洪水淹没区进行考察,在下游洪水沉积物保存完好的地点获取21.0 cm长岩芯DH1,并进行粒度、 烧失量、 磁化率和孢粉...  相似文献   

14.
The increasing natural disasters, especially floods during the last quarter century, are raising the economic losses in Taiwan. The most severe hazard in Taiwan is flooding induced by typhoons and storms in summer and autumn. By comparing the rivers around the world, the ones in Taiwan have the steepest slopes, the largest discharge per unit drainage area, and the shortest time of concentrations. Rapid urbanization without proper land uses managements usually worsen the flood problems. Consequently, flood hazards mitigation has become the most essential task for Taiwan to deal with. Although the government keeps improving flood defense structures, the flood damage grows continuously. In this article, possible flood mitigation strategies are identified for coping with complex environmental and social decisions with flood risk involved.  相似文献   

15.
In the time of the flooding, rural people in Bangladesh suffer from the lingering effects of labor market disruption and income deficiency. This study shows a model based analysis on the research question, ??what coping strategies are followed by the flooded households in Bangladesh and how???. Data are collected through a three stage stratified random sampling technique on 595 flooded and rural households??. Survey is carried out aftermath of the flood in the year 2005, from four different districts in Bangladesh. A major proportion of households are found to borrow money or resources from informal sources, such as nearby shops or the pharmacy, friends or relatives, or local money lenders, to buy food items and other essentials. A censored tobit model analysis shows that households initiate coping with borrowing money after the realization of floods, and gradually lead to cope with savings and selling assets as the duration of flood increases.  相似文献   

16.
Most of the countries around the North Indian Ocean are threatened by storm surges associated with severe tropical cyclones. The destruction due to the storm surge flooding is a serious concern along the coastal regions of India, Bangladesh, Myanmar, Pakistan, Sri Lanka, and Oman. Storm surges cause heavy loss of lives and property damage to the coastal structures and losses of agriculture which lead to annual economic losses in these countries. About 300,000 lives were lost in one of the most severe cyclones that hit Bangladesh (then East Pakistan) in November 1970. The Andhra Cyclone devastated part of the eastern coast of India, killing about 10,000 persons in November 1977. More recently, the Chittagong cyclone of April 1991 killed 140,000 people in Bangladesh, and the Orissa coast of India was struck by a severe cyclonic storm in October 1999, killing more than 15,000 people besides enormous loss to the property in the region. These and most of the world’s greatest natural disasters associated with the tropical cyclones have been directly attributed to storm surges. The main objective of this article is to highlight the recent developments in storm surge prediction in the Bay of Bengal and the Arabian Sea.  相似文献   

17.
Analyses of flood disasters were conducted using 1950–2001 data on the flood-damaged areas of cropland, the annual number of flood disasters and the direct economic losses in Xinjiang. There is an increasing trend in flood disasters in Xinjiang during the second half of the 20th century, especially since the mid-1980s. Results of a non-parametric Mann–Kendall test on the cropland-flooded index time series revealed an abrupt change in the mid-1980s. The reasons are discussed with respect to changes in annual precipitation and regional human activities, by correlating cropland-flooded area to annual precipitation and three socio-economic parameters (population, cropland area and GDP). The correlation coefficients between the flood-damaged area and the annual precipitation during the periods 1961–1998 and 1987–1998 were substantially higher than during the period of 1961–1986. The correlation coefficients between the flood-damaged area and the three human activity parameters, however, were relatively high for the whole period of 1961–1998, but generally not significant for the 1961–1986 and 1987–1998 periods, separately. These suggest that the occurrence of flood disasters could be mainly induced by local human activities before the mid-1980s, and thereafter mainly by abnormal precipitation in Xinjiang. Meteorological and hydrological records showed that the number of heavy rainfall events and the frequency of rainstorm flood disasters increased since the 1980s. In addition, siltation of reservoirs and loss of flood control structures are partly responsible for the increase of flood-damaged area. These results suggest that the increasing trend in flood disasters in Xinjiang since the middle 1980s could be attributed, at least in part, to an increasing trend in annual precipitation.  相似文献   

18.
The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by sub-bottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores. Based on the synthesis of major environmental changes in the NW Alps and on the age-depth model covering the past 7500 years in Lake Le Bourget, periods of enhanced Rhone River flood events in the lake can be related to abrupt climate changes and/or to increasing land use since c. 2700 cal. yr BP. For example, significant land use under rather stable climate conditions during the Roman Empire may be responsible for large flood deposits in the northern part of Lake Le Bourget between AD 966 and 1093. However, during the Little Ice Age (LIA), well-documented major environmental changes in the catchment area essentially resulted from climate change and formed basin-wide major flood deposits in Lake Le Bourget. Up to five 'LIA-like' Holocene cold periods developing enhanced Rhone River flooding activity in Lake Le Bourget are documented at c. 7200, 5200, 2800, 1600 and 200 cal. yr BP. These abrupt climate changes were associated in the NW Alps with Mont Blanc glacier advances, enhanced glaciofluvial regimes and high lake levels. Correlations with European lake level fluctuations and winter precipitation regimes inferred from glacier fluctuations in western Norway suggest that these five Holocene cooling events at 45°N were associated with enhanced westerlies, possibly resulting from a persistent negative mode of the North Atlantic Oscillation.  相似文献   

19.
梯级水库优化调度的有后效性动态规划模型及应用   总被引：23，自引：0，他引：23       下载免费PDF全文
梅亚东 《水科学进展》2000,11(2):194-198
建立了梯级水库在洪水期间发电调度的优化模型,由于含有河道洪水演进方程,该模型成为一类有后效性的动态规划模型.提出了两种新的解法——多维动态规划近似解法与有后效性动态规划逐次逼近算法.实例研究表明:这两种解法可行,结果合理,特别是逐次逼近算法计算更快速,是求解这类问题的有效的方法.  相似文献   

20.
Coastal inundation and damage exposure estimation: a case study for Jakarta   总被引：2，自引：2，他引：0  
Coastal flooding poses serious threats to coastal areas, and the vulnerability of coastal communities and economic sectors to flooding will increase in the coming decades due to environmental and socioeconomic changes. It is increasingly recognised that estimates of the vulnerability of cities are essential for planning adaptation measures. Jakarta is a case in point, since parts of the city are subjected to regular flooding on a near-monthly basis. In order to assess the current and future coastal flood hazard, we set up a GIS-based flood model of northern Jakarta to simulate inundated area and value of exposed assets. Under current conditions, estimated damage exposure to extreme coastal flood events with return periods of 100 and 1,000 years is high (€4.0 and €5.2 billion, respectively). Under the scenario for 2100, damage exposure associated with these events increases by a factor 4–5, with little difference between low/high sea-level rise scenarios. This increase is mainly due to rapid land subsidence and excludes socioeconomic developments. We also develop a detemporalised inundation scenario for assessing impacts associated with any coastal flood scenario. This allows for the identification of critical points above which large increases in damage exposure can be expected and also for the assessment of adaptation options against hypothetical user-defined levels of change, rather than being bound to a discrete set of a priori scenarios. The study highlights the need for urgent attention to the land subsidence problem; a continuation of the current rate would result in catastrophic increases in damage exposure.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号