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1.

Frequent flood is a concern for most of the coastal regions of India. The importance of flood maps in governing strategies for flood risk management is of prime importance. Flood inundation maps are considered dependable output generated from simulation results from hydraulic models in evaluating flood risks. In the present work, a continuous hydrologic-hydraulic model has been implemented for mapping the flood, caused by the Baitarani River of Odisha, India. A rainfall time-series data were fed into the hydrologic model and the runoff generated from the model was given as an input into the hydraulic model. The study was performed using the HEC-HMS model and the FLO-2D model to map the extent of flooding in the area. Shuttle Radar Topographic Mission (SRTM) 90 m Digital Elevation Model (DEM) data, Land use/Land cover map (LULC), soil texture data of the basin area were used to compute the topographic and hydraulic parameters. Flood inundation was simulated using the FLO-2D model and based on the flow depth, hazard zones were specified using the MAPPER tool of the hydraulic model. Bhadrak District was found to be the most hazard-prone district affected by the flood of the Baitarani River. The result of the study exhibited the hydraulic model as a utile tool for generating inundation maps. An approach for assessing the risk of flooding and proper management could help in mitigating the flood. The automated procedure for mapping and the details of the study can be used for planning flood disaster preparedness in the worst affected area.

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2.
Floods have been the most severe natural disasters in the West Black Sea Region of Turkey for many years; therefore Ulus Basin is selected as a study area for a thorough hydrologic flood analysis. The lack of embankments around the Ulus River and careless changes to the riverbed made by villagers, resulted in major flood events in the basin, causing significant damage in the area. In this study, the hydrodynamic characteristics of the basin and the riverbed are determined by calibrating the hydraulic module of the MIKE 11 modeling system with the observed 1991 flood. Then, for the 25-, 50- and 100-year floods the highest water levels in the river are forecasted by integration of the MIKE 11 hydrologic and hydraulic modules. Afterwards, inundation maps are obtained by using together the hydraulic and GIS modules of the MIKE 11 system.  相似文献   

3.
A comprehensive flood risk assessment should aim not only at quantifying uncertainties but also the variability of risk over time. In this study, an efficient modelling framework was proposed to perform probabilistic hazard and risk analysis in dike-protected river systems accounting for morphological variability and uncertainty. The modelling framework combined the use of: (1) continuous synthetic discharge forcing, (2) a stochastic dike breach model dynamically coupled to a stochastic unsteady one-dimensional hydraulic model (MIKE1D) describing river flows, (3) a catalogue of pre-run probabilistic inundation maps (MIKE SHE) and (4) a damage and loss model (CAPRA). The methodology was applied using continuous simulations to a 45-km reach of the Upper Koshi River, Nepal, to investigate the changes in breach and flood hazards and subsequent risks after 2 and 5 years of probable river bed aggradation. The study results indicated an increase in annual average loss of 4% per year driven by changes in loss distribution in the most frequent loss return periods (20–500 years). The use of continuous simulations and dike breach model also provided a more robust estimation of risk metrics as compared to traditional binary treatment of flood defence and/or the direct association of flow with loss return periods. The results were helpful to illustrate the potential impacts of dynamic river morphology, dike failure and continuous simulation and their significance when devising flood risk study methodologies.  相似文献   

4.
Flood inundation maps are dependent on the topographic and geomorphologic features of a wadi (drainage basin) in arid regions, which are most susceptible for potential flash flood occurrences, such as in the southwestern part of the Kingdom of Saudi Arabia. It is not possible to control the potential flood hazards by using only technological instruments that forewarn the occurrences or imminence. Additionally, it would be better to prepare flood risk maps so as to delineate the risky areas to educate the administrators and local settlers. The availability of these maps is the key requirement for any urban development that entails land use allocation, identification of dam, tunnel, highway, bridge sites, and infrastructure locations for sustainable future. This paper suggests the necessary steps in flood inundation map preparation after determining the possible flood discharge. For this purpose, a set of critical cross-sections along the possible flood plain are taken in the field with surveying methods and measurements. The calculation of the average flow velocity in each section is calculated according to the cross-section geometric, hydraulic, and material properties. Synthetic rating curves (SRC) are prepared for each cross section, which are very useful especially in arid and semi-arid regions where there are no perennial surface water flows for natural rating curve measurements. All the SRCs appear in the form of power function which relates the flow depth to discharge in a given cross section. It is then possible to calculate the flood depth in the cross section through its SRC. Depending on the cross-section shape, the flood width can be calculated. The connection of a series of widths on a scaled topographic map delineates the flood inundation area. If digital elevation map (DEM) is available, then the SRCs can be integrated with these maps and the flood inundation delineation can be achieved automatically. Since DEMs are not available, the topographic maps are used for this purpose in order to delineate flood inundation areas within wadis Hali and Yiba from the southwestern Kingdom of Saudi Arabia.  相似文献   

5.
The paper presents a consistent micro-scale flood risk analysis procedure, relying on detailed 2D inundation modelling as well as on high resolution topographic and land use database. The flow model is based on the shallow-water equations, solved by means of a finite volume scheme on multi-block structured grids. Using highly accurate laser altimetry, the simulations are performed with a typical grid spacing of 2 m, which is fine enough to represent the flow at the scale of individual buildings. Consequently, the outcomes of hydraulic modelling constitute suitable inputs for the subsequent exposure analysis, performed at a micro-scale using detailed land use maps and geographic database. Eventually, the procedure incorporates social flood impact analysis and evaluation of direct economic damage to residential buildings. Besides detailing the characteristics and performance of the hydraulic model, the paper describes the flow of data within the overall flood risk analysis procedure and demonstrates its applicability by means of a case study, for which two different flood protection measures were evaluated.  相似文献   

6.
Surat city of India, situated 100 km downstream of Ukai Dam and 19.4 km upstream from the mouth of River Tapi, has experienced the largest flood in 2006. The peak discharge of about 25,770 m3 s?1 released from the Ukai Dam was responsible for a disaster. To assess the flood and find inundation in low-lying areas, simulation work is carried out under the 1D/2D couple hydrodynamic modeling. Two hundred ninety-nine cross sections, two hydraulic structures and five major bridges across the river are considered for 1D modeling, whereas a topographic map at 0.5 m contour interval was used to produce a 5 m grid, and SRTM (30 and 90 m) grid has been considered for Surat and the Lower Tapi Basin. The tidal level at the river mouth and the release from the Ukai Dam during 2006 flood are considered as the downstream and upstream boundaries, respectively. The model is simulated under the unsteady flow condition and validated for the year 2006. The simulated result shows that 9th August was the worst day in terms of flooding for Surat city and a maximum 75–77% area was under inundation. Out of seven zones, the west zone had the deepest flood and inundated under 4–5 m. Furthermore, inundation is simulated under the bank protection work (i.e., levees, retaining wall) constructed after the 2006 flood. The simulated results show that the major zones are safe against the inundation under 14,430 m3 s?1 water releases from Ukai Dam except for the west zone. The study shows the 2D capability of new HEC-RAS 5 for flood inundation mapping and management studies.  相似文献   

7.
Floods are regular feature in rapidly urbanizing Dhaka, the capital city of Bangladesh. It is observed that about 60% of the eastern Dhaka regularly goes under water every year in monsoon due to lack of flood protection. Experience gathered from past devastating floods shows that, besides structural approach, non-structural approach such as flood hazard map and risk map is effective tools for reducing flood damages. In this paper, assessment of flood hazard by developing a flood hazard map for mid-eastern Dhaka (37.16 km2) was carried out by 1D hydrodynamic simulation on the basis of digital elevation model (DEM) data from Shuttle Radar Topography Mission and the hydrologic field-observed data for 32 years (1972–2004). As the topography of the area has been considerably changed due to rapid land-filling by land developers which was observed in recent satellite image (DigitalGlobe image; Date of imagery: 7th March 2007), the acquired DEM data were modified to represent the current topography. The inundation simulation was conducted using hydrodynamic program HEC-RAS for flood of 100-year return period. The simulation has revealed that the maximum depth is 7.55 m at the southeastern part of that area and affected area is more than 50%. A flood hazard map was prepared according to the simulation result using the software ArcGIS. Finally, to assess the flood risk of that area, a risk map was prepared where risk was defined as the product of hazard (i.e., depth of inundation) and vulnerability (i.e., the exposure of people or assets to flood). These two maps should be helpful in raising awareness of inhabitants and in assigning priority for land development and for emergency preparedness including aid and relief operations in high-risk areas in the future.  相似文献   

8.
为了准确分析洪涝灾害对防洪体系现状的影响，做出相应的防洪减灾措施，以浙江省台州市灵江下游流域为研究区域，构建了基于Saint-Venant方程的水动力学耦合模型，对河道溃决洪水过程进行实时仿真模拟。综合考虑研究区域地形、气象、水文资料、水利工程、下垫面条件等因素，在一维河网模型和二维水动力学模型耦合衔接中，最大程度还原真实地形中河槽内外的水流交互淹没，借助研究区域内典型台风暴雨资料，率定验证本文建立的一维-二维耦合水动力学模型，检验后的模型可实现灵江下游沿岸城市不同量级设计洪水及历史洪水的实时淹没过程模拟。模型计算结果表明，该模型模拟复杂地形条件情况下流域洪水实时演进过程达到了较高精度，在水系沿程典型断面水位计算值与实测值误差不超过0.1 m。  相似文献   

9.
The objective of this work was the estimation of time-space hydraulic (water depth, flow velocity) and morphological (sediment transport and bank erosion) characteristics in the downstream part of a Mediterranean stream under current and future climatic conditions. The two-dimensional hydraulic model MIKE 21C was used, which has been developed specifically to simulate 2D flow and morphological changes in rivers. The model is based on an orthogonal curvilinear grid and comprises two parts: (a) the hydrodynamic part and (b) the morphological changes part. The curvilinear grid and the bathymetry file were generated using a very high-resolution DEM (1 m × 1 m). Time series discharge data from a hydrometric station introduced in the hydrodynamic part of the model. Regarding the morphological part of the model, field measurements of suspended sediment concentration and of bank erosion were used. The model was calibrated and verified using field data that were collected during high and low flow discharges. Model simulation was in good agreement with field observations as indicated by a variety of statistical measures. Next, for predicting the riverbank change, future meteorological data and river flow data for the next 10 years (2017–2027) were employed. These data series were created according to a lower and a higher emission climate change scenario. Based on the results, an increase in rainfall intensity may cause significant changes in river banks after 10 years (more than 5 m of soil loss in river meanders). Using the obtained simulation results, extreme hydrological events such as floods transporting large sediment loads and changes in river morphology can be monitored. The proposed methodology was applied to the downstream part of the Koiliaris River Basin in Crete, Greece.  相似文献   

10.
Applied flood risk analyses, especially in urban areas, very often pose the question how detailed the analysis needs to be in order to give a realistic figure of the expected risk. The methods used in research and practical applications range from very basic approaches with numerous simplifying assumptions up to very sophisticated, data and calculation time demanding applications both on the hazard and on the vulnerability part of the risk. In order to shed some light on the question of required model complexity in flood risk analyses and outputs sufficiently fulfilling the task at hand, a number of combinations of models of different complexity both on the hazard and on the vulnerability side were tested in a case study. The different models can be organized in a model matrix of different complexity levels: On the hazard side, the approaches/models selected were (A) linear interpolation of gauge water levels and intersection with a digital elevation model (DEM), (B) a mixed 1D/2D hydraulic model with simplifying assumptions (LISFLOOD-FP) and (C) a Saint-Venant 2D zero-inertia hyperbolic hydraulic model considering the built environment and infrastructure. On the vulnerability side, the models used for the estimation of direct damage to residential buildings are in order of increasing complexity: (I) meso-scale stage-damage functions applied to CORINE land cover data, (II) the rule-based meso-scale model FLEMOps+ using census data on the municipal building stock and CORINE land cover data and (III) a rule-based micro-scale model applied to a detailed building inventory. Besides the inundation depths, the latter two models consider different building types and qualities as well as the level of private precaution and contamination of the floodwater. The models were applied in a municipality in east Germany, Eilenburg. It suffered extraordinary damage during the flood of August 2002, which was well documented as were the inundation extent and depths. These data provide an almost unique data set for the validation of flood risk analyses. The analysis shows that the combination of the 1D/2D model and the meso-scale damage model FLEMOps+ performed best and provide the best compromise between data requirements, simulation effort, and an acceptable accuracy of the results. The more detailed approaches suffered from complex model set-up, high data requirements, and long computation times.  相似文献   

11.
In many parts of Canada, limited data are available for hydrodynamic model inputs, and the ability to generate quality flood grids through 1D, 2D or 3D methods is nonviable. In this paper, the capability of simplified flood models, which rely solely on digital terrain models (DTMs), was explored to assess the quality and speed of their results. Results were validated against historic floods in two locations. Three non-physics-based simplified conceptual flood models were tested: (1) planar method, (2) inclined plane and (3) height above nearest drainage network (HAND) model. The accuracy and performance were evaluated using three criteria: inundation extent, water depth and computation time. Findings show that the HAND model is the best predictor of inundation extent, with Probability of Detection and Critical Success Index being higher than 0.90 in both study areas. Though the preprocessing time for the HAND model is lengthy, once completed, the time to simulate flooding at a variety of water levels is rapid, making this model the most suitable choice for web-based, on-demand flood inundation mapping. Knowledge of the fit of these flood models and associated uncertainty can be helpful to emergency managers such that they can better understand exposure and vulnerability while preparing flood response plans.  相似文献   

12.
In fluvial systems, the relationship between a dominant variable (e.g. flood pulse) and its dependent ones (e.g. riparian vegetation) is called connectivity. This paper analyzes the connectivity elements and processes controlling riparian vegetation for a reach of the upper Paraná River (Brazil) and estimates the future changes in channel-vegetation relationship as a consequence of the managing of a large dam. The studied reach is situated 30 km downstream from the Porto Primavera Dam (construction finished in 1999). Through aerial photography (1:25,000, 1996), RGB-CBERS satellite imagery and a previous field botany survey it was possible to elaborate a map with the five major morpho-vegetation units: 1) Tree-dominated natural levee, 2) Shrubby upper floodplain, 3) Shrub-herbaceous mid floodplain, 4) Grass-herbaceous lower floodplain and 5) Shrub-herbaceous flood runoff channel units. By use of a detailed topographic survey and statistical tools each morpho-vegetation type was analyzed according to its connectivity parameters (frequency, recurrence, permanence, seasonality, potamophase, limnophase and FCQ index) in the pre- and post-dam closure periods of the historical series. Data showed that most of the morpho-vegetation units were predicted to present changes in connectivity parameters values after dam closing and the new regime could affect, in different intensity, the river ecology and particularly the riparian vegetation. The methods used in this study can be useful for dam impact studies in other South American tropical rivers.  相似文献   

13.
In the tropical and subtropical wet and dry regions, maintaining natural hydrologic connections between coastal rivers and adjacent ephemeral wetlands is critical to conserving and sustaining high levels of fisheries production within these systems. Though there is a consensus that there is a need to maintain these natural connections, little is known about what attributes of floodplain inundation regimes are most important in sustaining fisheries production. Two attributes of the flood season and thus floodplain inundation that may be particularly influential to fisheries are the amplitude of the flood season (floodplain water depth and spatial extent of inundation) and the duration of the flood season (i.e., time floodplains are inundated). In mangrove-dominated Everglades coastal rivers, seasonal inundation of upstream marsh floodplains may play an important role in provisioning recreational fisheries; however, this relationship remains unknown. Using two Everglades coastal river fisheries as a model, we tested whether the amplitude of the flood season or the duration of the flood season is more important in explaining variation in angler catch records of common snook and largemouth bass collected from 1992 to 2012. We validated angler catches with fisheries-independent electrofishing conducted in the same region from 2004 to 2012. Our results showed (1) that bass angler catches tracked electrofishing catches, while snook catches were completely mismatched. And (2) that previous year's marsh dynamics, particularly the duration of the flood season, was more influential than the flood season amplitude in explaining variation in bass catches, such that bass angler catches were negatively correlated to the period time that floodplains remained disconnected from coastal rivers in the previous year, while snook catches were not very well explained by floodplain inundation terms.  相似文献   

14.
Pasquier  Ulysse  He  Yi  Hooton  Simon  Goulden  Marisa  Hiscock  Kevin M. 《Natural Hazards》2019,98(3):915-937

Coastal regions are dynamic areas that often lie at the junction of different natural hazards. Extreme events such as storm surges and high precipitation are significant sources of concern for flood management. As climatic changes and sea-level rise put further pressure on these vulnerable systems, there is a need for a better understanding of the implications of compounding hazards. Recent computational advances in hydraulic modelling offer new opportunities to support decision-making and adaptation. Our research makes use of recently released features in the HEC-RAS version 5.0 software to develop an integrated 1D–2D hydrodynamic model. Using extreme value analysis with the Peaks-Over-Threshold method to define extreme scenarios, the model was applied to the eastern coast of the UK. The sensitivity of the protected wetland known as the Broads to a combination of fluvial, tidal and coastal sources of flooding was assessed, accounting for different rates of twenty-first century sea-level rise up to the year 2100. The 1D–2D approach led to a more detailed representation of inundation in coastal urban areas, while allowing for interactions with more fluvially dominated inland areas to be captured. While flooding was primarily driven by increased sea levels, combined events exacerbated flooded area by 5–40% and average depth by 10–32%, affecting different locations depending on the scenario. The results emphasise the importance of catchment-scale strategies that account for potentially interacting sources of flooding.

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15.
Due to increasing flood severities and frequencies, studies on coastal vulnerability assessment are of increasing concern. Evaluation of flood inundation depth and extent is the first issue in flood vulnerability analysis. This study has proposed a practical framework for reliable coastal floodplain delineation considering both inland and coastal flooding. New York City (NYC) has been considered as the case study because of its vulnerability to storm surge-induced hazards. For floodplain delineation, a distributed hydrologic model is used. In the proposed method, the severities of combined inland and coastal floods for different recurrence intervals are determined. Through analyzing past storms in the study region, a referenced (base) configuration of rainfall and storm surge is selected to be used for defining flood scenarios with different return periods. The inundated areas are determined under different flooding scenarios. The inundation maps of 2012 superstorm Sandy in NYC is simulated and compared with the FEMA revised maps which shows a close agreement. This methodology could be of significant value to the planners and engineers working on the preparedness of coastal urban communities against storms by providing a platform for updating inundation maps as new events are observed and new information becomes available.  相似文献   

16.
Extreme sea-level events (e.g. caused by storm surges) can cause coastal flooding, and considerable disruption and damage. To understand the impacts or hazards expected by different sea levels, waves and defence failures, it is useful to monitor and analyse coastal flood events, including generating numerical simulations of floodplain inundation. Ideally, any such modelling should be calibrated and validated using information recorded during real events, which can also add plausibility to synthetic flood event simulations. However, such data are rarely compiled for coastal floods. This paper demonstrates the capture of such a flood event dataset, and its integration with defence and floodplain modelling to reconstruct, archive and better understand the regional impacts of the event. The case-study event comprised a significant storm surge, high tide and waves in the English Channel on 10 March 2008, which resulted in flooding in at least 37 distinct areas across the Solent, UK (mainly due to overflow and outflanking of defences). The land area flooded may have exceeded 7 km2, with the breaching of a shingle barrier at Selsey contributing to up to 90 % of this area. Whilst sea floods are common in the Solent, this is the first regional dataset on flood extent. The compilation of data for the validation of coastal inundation modelling is discussed, and the implications for the analysis of future coastal flooding threats to population, business and infrastructure in the region.  相似文献   

17.
The Citarum River is one of the strategic rivers in West Java, Indonesia. Its total watershed area is approximately 1800 km2. Almost every year, the overflow from the Citarum River causes the inundation of most of the upper Citarum River watershed. To prevent and mitigate flood damage, it is necessary to understand the flooding characteristics. The region, however, suffers from a lack of observational data. Therefore, to analyze the inundation caused by flooding in the upper Citarum River watershed, a rainfall–runoff–inundation (RRI) model was employed. It used the following multiple satellite-derived datasets as input data as well as for model verification: Global Satellite Mapping of Precipitation, Hydrological data and maps based on Shuttle elevation Derivatives at multiple scales, Global Mosaics of the standard MODIS land cover type data product, and Landsat 7 satellite images. Parameter calibration was performed using a Monte Carlo simulation. The simulation was performed for February 2010. The results of this study show that the RRI model identifies inundation areas in large-scale river watersheds more effectively when using multiple satellite-derived datasets compared with the observed inundation map obtained from JICA in 2010 and Landsat 7 images. The model results can be improved if high-quality observed rainfall data, topographic data, and river cross-sectional data are available.  相似文献   

18.
An evaluation of morphometric parameters of two drainage networks derived from different sources was done to determine the influence of sub-basins to flooding on the main channel in the Havran River basin (Balıkesir-Turkey). Drainage networks for the sub-basins were derived from both topographic maps scaled 1:25.000 and a 10-m resolution digital elevation model (DEM) using geographic information systems (GIS). Blue lines, representing fluvial channels on the topographic maps were accepted as a drainage network, which does not depict all exterior links in the basin. The second drainage network was extracted from the DEM using minimum accumulation area threshold to include all exterior links. Morphometric parameters were applied to the two types of drainage networks at sub-basin levels. These parameters were used to assess the influence of the sub-basins on the main channel with respect to flooding. The results show that the drainage network of sub-basin 4—where a dam was constructed on its outlet to mitigate potential floods—has a lower influence morphometrically to produce probable floods on the main channel than that of sub-basins 1, 3, and 5. The construction of the dam will help reduce flooding on the main channel from sub-basin 4 but it will not prevent potential flooding from sub-basin 1, 3 and 5, which join the main channel downstream of sub-basin 4. Therefore, flood mitigation efforts should be considered in order to protect the settlement and agricultural lands on the floodplain downstream of the dam. In order to increase our understanding of flood hazards, and to determine appropriate mitigation solutions, drainage morphometry research should be included as an essential component to hydrologic studies.  相似文献   

19.
Midstream of the Keelung River Basin in Northern Taiwan has become highly urbanized and densely populated area. Flood inundation along riversides frequently occurred during typhoons or rainstorms. Three protection measures, including constructions of high-level protection levees, a diversion channel, and a detention reservoir, were proposed for flood mitigation. The main purpose of this study is to evaluate the flood mitigation performance of the three proposed structural measures by using combined hydrologic analyses and hydraulic routings. A semi-distributed parallel-type linear reservoirs rainfall-runoff model was used for estimating the surface runoff. Furthermore, a 1-D dynamic channel routing model was coupled with a two-dimensional inundation model to simulate the hydraulic characteristics of river flooding and overland flow. Simulation results of flood stages, runoff peak discharges, and inundation extent under design rainfall scenarios were chosen as the criteria for evaluation. The results showed a diversion channel is superior to the other two measures for flood mitigation of the study area. After the process of environmental impact assessment, a revised diversion channel approach has been approved for construction as the major structural measure.  相似文献   

20.
Huangpu River floodplain is historically vulnerable to flooding due to its location in the path of tropical cyclones, low elevation, relatively flat topography, rapid changes in sea level and fast rate of land subsidence due to urbanization. This paper presents a scenario-based study that investigates the fluvial flood potentials in the Huangpu River floodplain. Flood scenarios with return periods of 50, 100, 200, 500 and 1,000 years were designed to cover the probable situations. Further, a flood inundation model (FloodMap) that tightly couples a river flow model with a 1D solution of the full form of the St. Venant equations and a 2D floodplain flow model was used to predict the river flow and inundation extents. Flood characteristics obtained from the simulations were used in the exposure analysis to determine the spatial distribution of susceptible land uses under different scenarios. Results suggest that overtopping inundation mainly occurs within 1–2 km of the banks of the Huangpu River, with larger inundation extent predicted in the upper and middle reaches of the channel, a result of varying protection levels from relatively rural upstream to high urbanized floodplain in the vicinity of the middle reaches.  相似文献   

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