scholarly journals Managing Flood Hazard in a Complex Cross-Border Region Using Sentinel-1 SAR and Sentinel-2 Optical Data: A Case Study from Prut River Basin (NE Romania)

2021 ◽  
Vol 13 (23) ◽  
pp. 4934
Author(s):  
Cătălin I. Cîmpianu ◽  
Alin Mihu-Pintilie ◽  
Cristian C. Stoleriu ◽  
Andrei Urzică ◽  
Elena Huţanu

In this study, an alternative solution for flood risk management in complex cross-border regions is presented. In these cases, due to different flood risk management legislative approaches, there is a lack of joint cooperation between the involved countries. As a main consequence, LiDAR-derived digital elevation models and accurate flood hazard maps obtained by means of hydrological and hydraulic modeling are missing or are incomplete. This is also the case for the Prut River, which acts as a natural boundary between European Union (EU) member Romania and non-EU countries Ukraine and Republic of Moldova. Here, flood hazard maps were developed under the European Floods Directive (2007/60/EC) only for the Romanian territory and only for the 1% exceeding probability (respectively floods that can occur once every 100 years). For this reason, in order to improve the flood hazard management in the area and consider all cross-border territories, a fully remote sensing approach was considered. Using open-source SAR Sentinel-1 and Sentinel-2 data characterized by an improved temporal resolution, we managed to capture the maximum spatial extent of a flood event that took place in the aforementioned river sector (middle Prut River course) during the 24 and 27 June 2020. Moreover, by means of flood frequency analysis, the development of a transboundary flood hazard map with an assigned probability, specific to the maximum flow rate recorded during the event, was realized.

2021 ◽  
Vol 11 (14) ◽  
pp. 6629
Author(s):  
Julio Garrote ◽  
Evelyng Peña ◽  
Andrés Díez-Herrero

All flood hazard and risk assessment suffer from a certain degree of uncertainty due to multiple factors, such as flood frequency analysis, hydrodynamic model calibration, or flood damage (magnitude–damage functions) models. The uncertainty linked to the flood frequency analysis is one of the most important factors (previous and present estimation point to 40%). Flood frequency analysis uncertainty has been approached from different points of view, such as the application of complex statistical models, the regionalization processes of peak flows, or the inclusion of non-systematic data. Here, we present an achievable approach to defining the uncertainty linked to flood frequency analysis by using the Monte Carlo method. Using the city of Zamora as the study site, the uncertainty is delimited by confidence intervals of a peak flow quantile of a 500-year return period. Probabilistic maps are derived from hydrodynamic results, and further analysis include flood hazard maps for human loss of stability and vehicle damage. Although the effect of this uncertainty is conditioned by the shape of the terrain, the results obtained may allow managers to achieve more consistent land-use planning. All those Zamora city results point out the probable underestimation of flood hazard (the higher hazard areas increase around 20%) and risk when the uncertainty analysis is not considered, thus limiting the efficiency of flood risk management tasks.


2015 ◽  
Vol 15 (6) ◽  
pp. 1297-1309 ◽  
Author(s):  
K. M. de Bruijn ◽  
F. Klijn ◽  
B. van de Pas ◽  
C. T. J. Slager

Abstract. For comprehensive flood risk management, accurate information on flood hazards is crucial. While in the past an estimate of potential flood consequences in large areas was often sufficient to make decisions on flood protection, there is currently an increasing demand to have detailed hazard maps available to be able to consider other risk-reducing measures as well. Hazard maps are a prerequisite for spatial planning, but can also support emergency management, the design of flood mitigation measures, and the setting of insurance policies. The increase in flood risks due to population growth and economic development in hazardous areas in the past shows that sensible spatial planning is crucial to prevent risks increasing further. Assigning the least hazardous locations for development or adapting developments to the actual hazard requires comprehensive flood hazard maps. Since flood hazard is a multi-dimensional phenomenon, many different maps could be relevant. Having large numbers of maps to take into account does not, however, make planning easier. To support flood risk management planning we therefore introduce a new approach in which all relevant flood hazard parameters can be combined into two comprehensive maps of flood damage hazard and flood fatality hazard.


2015 ◽  
Vol 3 (1) ◽  
pp. 123-159
Author(s):  
K. M. de Bruijn ◽  
F. Klijn ◽  
B. van de Pas ◽  
C. T. J. Slager

Abstract. For comprehensive flood risk management, accurate information on flood hazards is crucial. While in the past an estimate of potential flood consequences in large areas was often sufficient to make decisions on flood protection, there currently is an increasing demand to have detailed hazard maps available to be able to consider other risk reducing measures as well. Hazard maps are a prerequisite for spatial planning, but can also support emergency management, the design of flood mitigation measures, and the setting of insurance policies. The increase in flood risks due to population growth and economic development in hazardous areas in the past shows that sensible spatial planning is crucial to prevent risks increasing further. Assigning the least hazardous locations for development or adapting developments to the actual hazard requires comprehensive flood hazard maps. Since flood hazard is a multi-dimensional phenomenon, many different maps could be relevant. Having large numbers of maps to take into account does, however, not make planning easier. To support flood risk management planning we therefore introduce a new approach in which all relevant flood hazard parameters can be combined into two comprehensive maps of flood damage hazard respectively flood fatality hazard.


2021 ◽  
Author(s):  
◽  
Toni Kekez

Many river basins are experiencing frequent flooding events with significant economic and other losses due to intensive precipitation as well as other atmospheric and hydrological conditions. European Flood Directive defined flood risk as a combination of flooding probability and possible adverse consequences on people, assets, cultural heritage and environment. Flood risk management considers implementation of different measures for mitigation and prevention of possible negative consequences related to flooding. Uncertainty can strongly affect the flood risk management process, especially near and during the flood event. A framework is proposed for implementation of uncertainty related to behavior of the endangered system in the flood risk assessment, in order to improve the decision-making process during the flood emergency response. The proposed framework is validated on the City of Slavonski Brod pilot site, where the results demonstrated that there is a significant flood hazard still present due to possible weir failure, despite the improvement of flood defense measures. Furthermore, the results demonstrated how flood risk value can significantly decrease by properly evacuating the affected population. Flood risk management on a strategic level requires a monetary quantification of possible flood risk, which is performed by calculating expected annual damage (EAD) based on the combination of flooding event probability and corresponding damages. A semi-analytic methodology is presented for estimation of expected annual damage based on the factor graph model, which enables integration of entire probability space as well as flexibility in defining input data. Furthermore, a novel approach is presented for definition of annual damage distribution based on first and second statistical moment and by employing Beta distribution. By analyzing the annual damage distribution as well as impact of different sources of uncertainty, the results demonstrated that there is a significant impact of extreme events with low occurrence probability on the expected annual damage.


2020 ◽  
Author(s):  
B. Thanga Gurusamy ◽  
Avinash D Vasudeo ◽  
Aniruddha Dattatraya Ghare

<p><strong>Abstract: </strong>Because of the uncertainty and high cost involved, the Absolute Flood Protection has not been considered as a rational decision. Hence the trend is to replace Absolute Flood Protection strategy by Flood Risk Management Strategy. This Paper focus on the development of Multiple Criteria Decision Making (MCDM) model towards Flood Risk Management (FRM) across Godavari Lower Sub-Basin of India using GIS based methodologies for Flood Hazard Zonation in order to achieve global minimum of the Flood predicted Risk level.  Flood Hazard Zone Map for the historical flood events obtained with the use of GIS based Digital Elevation Models across the study area have been presented and used for the estimation of Hazard Risk. Uncertainty (or Control) Risk levels of each Flood estimated using various Flood Forecasting methodologies have been compared for the selected locations of the study area. Effectiveness of Passive Flood Protection Measures in the form of Flood Levees has been quantitatively analyzed for the increase in the Opportunity Risk and corresponding reduction in the Flood Hazard Risk. Various types of Multi-Objective Evolutionary Algorithms (MOEAs) have been used  to determine a Compromise solution with conflicting criteria between Hazard Risk and Opportunity (or Investment) Risk and the results were compared for each of the selected levels of Flood estimated with corresponding uncertainty. Traditional optimization method in the form of Pareto-Optimal Front have also been graphically depicted for the minimization of both Hazard Risk Objective function and Opportunity Risk Objective Function and compared with those obtained using MOEAs. Watershed wise distribution of optimized Flood Risk variation across the Sub-basin has been presented graphically for both the cases of with and without active Flood Routing Measures. <strong>Keywords:  </strong>Flood Risk Management; GIS based Flood Hazard Zonation; Multi-Criteria Decision Making; Multi-Objective Evolutionary Algorithms; Godavari Lower Sub-Basin of India;</p>


2020 ◽  
Author(s):  
Kiran Kezhkepurath Gangadhara ◽  
Srinivas Venkata Vemavarapu

<p>Flood hazard maps are essential for development and assessment of flood risk management strategies. Conventionally, flood hazard assessment is based on deterministic approach which involves deriving inundation maps considering hydrologic and hydraulic models. A flood hydrograph corresponding to a specified return period is derived using a hydrologic model, which is then routed through flood plain of the study area to estimate water surface elevations and inundation extent with the aid of a hydraulic model. A more informative way of representing flood risk is through probabilistic hazard maps, which additionally provide information on the uncertainty associated with the extent of inundation. To arrive at a probabilistic flood hazard map, several flood hydrographs are generated, representing possible scenarios for flood events over a long period of time (e.g., 500 to 1000 years). Each of those hydrographs is routed through the flood plain and probability of inundation for all locations in the plain is estimated to derive the probabilistic flood hazard map. For gauged catchments, historical streamflow and/or rainfall data may be used to determine design flood hydrographs and the corresponding hazard maps using various strategies. In the case of ungauged catchments, however, there is a dearth of procedures for prediction of flood hazard maps. To address this, a novel multivariate regional frequency analysis (MRFA) approach is proposed. It involves (i) use of a newly proposed clustering methodology for regionalization of catchments, which accounts for uncertainty arising from ambiguity in choice of various potential clustering algorithms (which differ in underlying clustering strategies) and their initialization, (ii) fitting of a multivariate extremes model to information pooled from catchments in homogeneous region to generate synthetic flood hydrographs at ungauged target location(s), and (iii) routing of the hydrographs through the flood plain using LISFLOOD-FP model to derive probabilistic flood hazard map. The MRFA approach is designed to predict flood hydrograph related characteristics (peak flow, volume and duration of flood) at target locations in ungauged basins by considering watershed related characteristics as predictor/explanatory variables. An advantage of the proposed approach is its ability to account for uncertainty in catchment regionalization and dependency between all the flood hydrograph related characteristics reliably. Thus, the synthetic flood hydrographs generated in river basins appear more realistic depicting the observed dependence structure among flood hydrograph characteristics. The approach alleviates several uncertainties found in conventional methods (based on conceptual, probabilistic or geomorphological approaches) which affect estimation of flood hazard. Potential of the proposed approach is demonstrated through a case study on catchments in Mahanadi river basin of India, which extends over 141,600 km<sup>2</sup> and is frequently prone to floods. Comparison is shown between flood hazard map obtained based on true at-site data and that derived based on the proposed MRFA approach by considering the respective sites to be pseudo-ungauged. Coefficient of correlation and root mean squared error considered for performance evaluation indicated that the proposed approach is promising.</p>


Author(s):  
O. M. Kozytskyi ◽  
S. A. Shevchuk ◽  
I. A. Shevchenko

Background of the study. Due to the increasing intensity and frequency of catastrophic floods occurrence, one of the most important tasks of the water management of Ukraine is to increase the efficiency of the existing system of flood protection due to the implementation of integrated flood risk management methods based on the assessment of flood hazard levels requirements according to Directive 2007/60/EC. The development of scientific and methodological bases for the assessment and mapping of flood hazard and risk levels, as well as the development of integrated flood risk management plans based on them, is an important and urgent task in Ukraine as an associated EU member. The purpose of the work is to highlight the main works results, performed at the Institute on the study of patterns of riverbed transformations, the development of strategies for flood risk management and scientific and methodological support of the assessment and mapping of flood hazard and risk, taking into account the nature and the intensity of river bed transformation and exogenous processes in river basins of Ukraine. Outline of the main material. Systematic research on flood protection issues and river bed evolution in IWPaLR has been conducted since the middle of the last century. The problems of the dynamics of river bed’s evolutions, ensuring the stability of dams, erosion of the tail water of dam, development of active hydraulic structures and their arrangement in river beds, forecasting river bed evolution, runoffs, development study of permissible (nondestructive) flow velocities for alluvial soils, taking into account the phenomenon of self-patching of the river bed, the dynamic equilibrium of the beds, the typing of the beds of mountain rivers, etc., were studied and solved under the natural conditions and in the hydraulic laboratory of the Institute. Based on the results of theoretical and experimental studies of river bed evolution, a number of methodological provisions on the complex regulation of channel deformations and safe passage of high floods were formulated and published a number of regulatory and methodological documents on the calculation and forecasting of river bed transformations, designing of dams and protection structures. An important role was given to the issues of regulation and redistribution of floodwater by the system of river reservoirs and replenishment of groundwater reserves. The methodological recommendations for sampling of river bed deposits and sediments, on the base of the international ISO standards’ requirements and recommendations of have been developed at the Institute, as well as the method of estimation of the river bed transformation’s dynamics, for the discrete and quantitative assessments of river bed deformations and their intensity. The paper also highlights the main results of work on the implementation of the Flood Directive 2007/60/EC in Ukraine, in particular, the development of a Flood Risk Management Strategy in the Ukrainian Carpathian River basins. In the Strategy declared the latest approaches to flood response, which foresee the abandonment of the current paradigm of "flood protection" to favor integrated flood risk management. It defines national mechanisms of strategic management in the field of flood risk reduction, directions of transboundary cooperation, coordination of works within river basins. For the future development of this Strategy, the paper presents the scientific and methodological bases for a comprehensive assessment of the total levels of flood hazard and flood risk and their mapping on a GIS basis. Conclusion. In the future, scientific research on integrated flood risk management should focus on the study of patterns of evolution of river bed and development of mathematical models of regulation of channel deformations, improvement of the flood forecasting and prevention methodology based on simulation modeling, as well as the development new management schemes for runoff ‘s regulation.


2021 ◽  
Vol 21 (10) ◽  
pp. 2921-2948
Author(s):  
Sara Lindersson ◽  
Luigia Brandimarte ◽  
Johanna Mård ◽  
Giuliano Di Baldassarre

Abstract. Riverine flood risk studies often require the identification of areas prone to potential flooding. This modelling process can be based on either (hydrologically derived) flood hazard maps or (topography-based) hydrogeomorphic floodplain maps. In this paper, we derive and compare riverine flood exposure from three global products: a hydrogeomorphic floodplain map (GFPLAIN250m, hereinafter GFPLAIN) and two flood hazard maps (Flood Hazard Map of the World by the European Commission's Joint Research Centre, hereinafter JRC, and the flood hazard maps produced for the Global Assessment Report on Disaster Risk Reduction 2015, hereinafter GAR). We find an average spatial agreement between these maps of around 30 % at the river basin level on a global scale. This agreement is highly variable across model combinations and geographic conditions, influenced by climatic humidity, river volume, topography, and coastal proximity. Contrary to expectations, the agreement between the two flood hazard maps is lower compared to their agreement with the hydrogeomorphic floodplain map. We also map riverine flood exposure for 26 countries across the global south by intersecting these maps with three human population maps (Global Human Settlement population grid, hereinafter GHS; High Resolution Settlement Layer, hereinafter HRSL; and WorldPop). The findings of this study indicate that hydrogeomorphic floodplain maps can be a valuable way of producing high-resolution maps of flood-prone zones to support riverine flood risk studies, but caution should be taken in regions that are dry, steep, very flat, or near the coast.


2009 ◽  
Vol 9 (2) ◽  
pp. 563-574 ◽  
Author(s):  
M. Hagemeier-Klose ◽  
K. Wagner

Abstract. Flood risk communication with the general public and the population at risk is getting increasingly important for flood risk management, especially as a precautionary measure. This is also underlined by the EU Flood Directive. The flood related authorities therefore have to develop adjusted information tools which meet the demands of different user groups. This article presents the formative evaluation of flood hazard maps and web mapping services according to the specific requirements and needs of the general public using the dynamic-transactional approach as a theoretical framework. The evaluation was done by a mixture of different methods; an analysis of existing tools, a creative workshop with experts and laymen and an online survey. The currently existing flood hazard maps or web mapping services or web GIS still lack a good balance between simplicity and complexity with adequate readability and usability for the public. Well designed and associative maps (e.g. using blue colours for water depths) which can be compared with past local flood events and which can create empathy in viewers, can help to raise awareness, to heighten the activity and knowledge level or can lead to further information seeking. Concerning web mapping services, a linkage between general flood information like flood extents of different scenarios and corresponding water depths and real time information like gauge levels is an important demand by users. Gauge levels of these scenarios are easier to understand than the scientifically correct return periods or annualities. The recently developed Bavarian web mapping service tries to integrate these requirements.


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