EU Floods Directive Research Articles

A comprehensive approach for assessing social flood vulnerability and social flood risk: The case of Denmark

Flood risk assessment approaches have traditionally been dominated by measures of economic damage. However, the importance of understanding the social impacts of flooding are increasingly being acknowledged. Social vulnerability indices have been constructed in diverse geographical contexts to understand relative susceptibility of different social groups to flood hazards. However, integrated assessments of social vulnerability, exposure, and hazard information are lacking. Here, we construct a national social vulnerability index (SVI) for Denmark and combine this with direct and indirect social exposure data and coastal flood hazard data to construct a national social flood risk index (SFRI). Results show the spatial distribution of social flood vulnerability and social flood risk in Denmark. Our findings illustrate that including social data in flood risk assessment could significantly change our understanding of flood risk on a national scale. Methodologically, our work introduces a comprehensive flood risk modelling approach that explicitly considers the social impacts of flooding in all model components. The application of this model in Denmark reveals that the social impacts of flooding extend far beyond flooded areas, thus highlighting the importance of explicitly considering direct and indirect social exposure in addition to social vulnerability in flood risk assessment. By introducing a comprehensive, socially specific approach to flood risk assessment that is usable within existing risk management frameworks such as the EU Floods Directive, our work aims to mainstream social wellbeing, resilience, and justice as central considerations in decision making on flood risk management.

Flood risk assessments—Exploring maturity and challenges in Sweden

AbstractFloods are destructive to society. Hence, to assess and manage flood risk is imperative. Flood risk assessments require several layers of analysis, from flood hazard to societal impact. This paper explores the maturity level and challenges related to three components of a comprehensive risk assessment: flood hazard, direct consequences, and indirect consequences. This is achieved by introducing and applying a maturity framework on flood hazard reports and flood risk management plans in Sweden, as required by the EU Floods Directive (FD). A longitudinal analysis is conducted over two FD cycles (2009–2015 and 2016–2021). Complementary interviews with county administrative boards and responsible authorities provide deeper insights into processes and practical challenges. The results reveal that the maturity level of flood hazard assessment is high, while direct and, in particular, indirect consequences assessments need increased attention and substantial improvements. Further, there is no significant increase in maturity between the FD cycles, indicating fundamental challenges towards achieving this. Critical steps forward include developing applicable methods for analysing both direct and indirect consequences of floods, improving data availability on functionality and interdependency of critical infrastructure and society at large, and creating incentives for a broader range of societal actors to participate in flood risk management.

Social network analysis of EU flood risk management plans: Case Finland

AbstractFlood risks are increasing in Europe, and the EU Floods Directive is one of the main efforts to implement and harmonize effective flood risk governance and management among member states. At the same time, the ongoing shift from mere flood protection to multi‐functional flood risk governance calls for increased collaboration among a diversity of actors, typically with varying interests and responsibilities. In this study, we analyze the actor networks unfolding from flood risk management plans to visualize the diversity of roles and connections between actors participating in flood risk management measures. We introduce a new framework for analyzing flood risk management plans and related actor networks using Social Network Analysis and test it in the context of Finland. The framework helps to visualize the diversity of networks for different flood risk management strategies. The analysis also reveals the central roles that different types of actors—including those outside the public sector—occupy in the network. The findings suggest that Social Network Analysis can be used in the context of EU flood risk governance and that flood risk management plans offer an excellent opportunity for comparative governance studies in the EU.

Riverine flood potential assessment using metaheuristic hybrid machine learning algorithms

AbstractThis study presents the performance of stand‐alone and novel hybrid models combining the feed‐forward neural network (FFNN) and extreme gradient boosting (XGB) with the genetic algorithm (GA) optimization to determine the riverine flood potential at a local spatial scale, which is represented by the Gidra river basin, Slovakia. Eleven flood factors and a robust flood inventory database, consisting of 10,000 flood and non‐flood locations, were used. Using the FFNN, XGB, GA‐FFNN and GA‐XGB models, 16.5%, 11.0%, 17.1%, and 12.3% of the studied basin, respectively, is characterized with high to very high riverine flood potential. The applied models resulted in very high accuracy, that is, AUC = 0.93 in case of the FFNN stand‐alone model and AUC = 0.96 in case of the XGB stand‐alone model. The GA algorithm was able to raise the value of AUC for the hybrid GA‐FFNN and GA‐XGB models to 0.94 and 0.97, respectively. The results of this study can be useful, especially, for the identification of the areas with the highest potential for riverine floods within the next updating of the Preliminary Flood Risk Assessment, which is being carried out based on the EU Floods Directive.

Indicator-based approach for fluvial flood risk assessment at municipal level in Slovakia

The article focuses on the mapping and assessment of fluvial flood risk at municipal level of Slovakia. The fluvial floods risk index (FFRI), composed of a hazard component and a vulnerability component, was computed for 2927 municipalities using spatial multicriteria analysis and geographic information systems (GIS). The fluvial flood hazard index (FFHI) was computed based on eight physical-geographical indicators and land cover representing the riverine flood potential and also the frequency of flood events in individual municipalities. The fluvial flood vulnerability index (FFVI) was calculated using seven indicators representing the economic and social vulnerability of municipalities. All of the indicators were normalized and weighted using the rank sum method. By aggregating the weighted indicators, we obtained the FFHI and FFVI in each municipality. The final FFRI is a result of a synthesis of the FFHI and FFVI. The results of this study can be used mainly in the framework of flood risk management at national spatial scale, but also for local governments and periodic update of the Preliminary Flood Risk Assessment document, which is carried out at the national level under the EU Floods Directive.

Pluvial Flash Flood Hazard and Risk Mapping in Croatia: Case Study in the Gospić Catchment

Since the beginning of the 21st Century, Europe has been affected by destructive floods. European Union Member States have an obligation to develop flood hazard and flood risk maps as support to the Flood Risk Management Plan (FRMP). The main objective of this study is to propose a methodological framework for hazard and risk assessment of pluvial flash floods in Croatia at the catchment level, which can be integrated into the FRMP. Therefore, a methodology based on the source–pathway–consequence approach for flood risk assessment is presented, which complies with the EU Floods Directive. This integrated and comprehensive methodology is based on high-resolution open data available for EU Member States. Three scenarios are defined for a low, medium, and high probability, defined by design storms of different durations. The proposed methodology consists of flood hazard analysis, vulnerability assessment, and risk analysis. Pluvial flash flood hazards are analyzed using a 2D hydrologic–hydraulic model. The flood vulnerability assessment consists of a GIS analysis to identify receptors potentially at risk of flooding and an assessment of susceptibility to potential flood damage using depth–damage curves. Flood risk is assessed both qualitatively in terms of risk levels and quantitatively in terms of direct damages expressed in monetary terms. The developed methodology was applied and tested in a case study in the Gospić catchment in Croatia, which surrounds a small rural town frequently affected by pluvial flash floods.

Human health in the flood risk management planning under the European Union Floods Directive: Pilot study in the Sava River Basin

The EU Floods Directive (2007/60/EC) has the purpose to establish a framework for the flood risks assessment and management. It requires the implementation of coordinated measures on a basin-wide level for the reduction of adverse consequences to human health and life. However, mainly direct fatalities are taken into consideration in these plans. To develop more integrated and adaptive risk management and governance it is important to include both direct and indirect consequences. To define effective measures clearer understanding of the relation between floods and impact on human health is needed. We present a first attempt to provide a roadmap for the inclusion of health issues of concern to flood risk management within the Sava River Basin as an example. An overview of the potential flood effects to health issues was made and a roadmap plan was set up to analyse and map these flood risks. We concluded that indirect health effects can contribute significantly to the overall adverse consequences to health, and although relations are complex, a preliminary assessment could be made. Mapping of adverse consequences to health issues in the planning stages should lead to systemic insights and proposed measures in the prevention, protection, and preparedness while considering the characteristics of the river basin or sub-basins. By incorporating a health-risk-analysis in the planning process, health-oriented preparation is not only aimed at improving post-flood relief efforts, but to minimise the actual impacts and decrease post flood recovery time and costs.

Confronting complexity

Confronting complexity

RESCUE: A geomorphology‐based, hydrologic‐hydraulic model for large‐scale inundation mapping

AbstractFlood mapping is a key stage for detecting vulnerable areas, assessing floods impacts, identifying damages, and mitigation plans. Despite of the available guidelines for flood mapping following EU Floods Directive, coherent and comprehensive official flood hazard maps at the national scale are still missing, at least in the EU. In fact, flood mapping generally requires high economical and computational costs for setup/calibration of hydrological/hydraulic models, leading to partial and fragmented vulnerable areas. Here, we propose RESCUE, a laRgE SCale inUndation modEl; the scope is providing a simple and inexpensive tool for flood mapping at the regional scale, overcoming the current fragmentation. RESCUE takes advantage from coupling geomorphological analysis and simplified hydrologic‐hydraulic modeling, providing simple and reliable large scales inundation estimates. It is as parsimonious as purely DTM‐based methods and physically based as any hydrodynamic model, yet computationally more efficient. The model allows for parametric uncertainty analysis for a probabilistic assessment of inundation areas. We demonstrate RESCUE potentialities and limitations using two illustrative examples: Paglia‐Chiani River system, and Central Apennines District (Central Italy). Notwithstanding the inaccuracies of large scale DTMs and the missed representation of flood‐structure interactions, results are promising, suggesting that RESCUE might be an effective tool for preliminary hazard assessment.

Riverine flood potential assessment at municipal level in Slovakia

Study regionSlovakia – 2927 municipalities. Study focusThis study maps and assesses the riverine flood potential in municipalities of Slovakia using the vector-based spatial multi-criteria analysis and geographic information systems (GIS). The flood potential index (FPI) in municipalities was computed based on eight flood factors, which were normalized, weighted and aggregated into the FPI index. Furthermore, we analyzed the spatial clusters of riverine flood potential using the local Moran’s coefficient of spatial autocorrelation. New hydrological insights for the regionThe very high and high FPI (767 municipalities) was recorded mostly in municipalities of northern and eastern Slovakia. Very low and low FPI (1452 municipalities) dominates in western and southern Slovakia while moderate FPI (708 municipalities) was mainly recorded in municipalities of central Slovakia. The number of statistically significant high-high and low-low spatial clusters of riverine flood potential was 16 (524 municipalities) and 18 (487 municipalities), respectively. Clusters of positive spatial autocorrelation are mostly located in the northern and eastern Slovakia, one cluster in western Slovakia and seven clusters in central Slovakia. Clusters of negative spatial autocorrelation are mostly located in western and southern Slovakia and three clusters in eastern Slovakia. The proposed methodology can be useful for regular updating of Preliminary Flood Risk Assessment (PFRA) in Slovakia under the EU Floods Directive.

Don’t Split Them Up! Landscape Design of Multifunctional Open Spaces Suitable for Coping with Flash Floods and River Floods

Pressures arising from agriculture, infrastructures and settlements have gradually reduced natural spaces of European watercourses limiting their self-regulation capacities, environmental and social potentials, resulting in widespread critical anthropic features. Dealing with flood phenomena adds artificiality, as several works for hydraulic protection are necessary. This was the case of Pistoia, a small city in the north of Tuscany, where the Ombrone stream, held in a straight-channeled course since the 18th century, sometimes breaks its embankments and floods the low plain from the southeast of Pistoia to downstream. Complying with the EU Floods Directive (2007/60/EC), the regional authority for flood risks planned some basins in the high plain upstream of Pistoia. A study we developed before this research assumed to shift the design approach from functional separation to full integration of hydraulic works in an area planned as an urban park for several years, but still in waiting. We now carried out a second study that adopts the concept of deep structure as the main design reference to “see” the park in the landscape features. This article concerns the research by the design process just developed to investigate a sustainable layout of the place new hydraulic asset as a basic landscape identity of the future park. Not to split spaces up with regard to their main functions was the general aim the process was focused on to combine an effective hydraulic protection with a full environmental and social enhancement of the urban park.

Real-time assessment of flash flood impacts at pan-European scale: The ReAFFINE method

The development of early warning systems (EWSs) is a key element for the effective mitigation of flash flood impacts. Emergency managers and other end-users increasingly recognise the benefit of tools that automatically translate the forecasted flash flood hazard (e.g. expressed in terms of peak discharge or return period) into the expected socio-economic impacts (e.g. the affected population). While previous studies aimed at forecasting flash flood impacts at local or regional scales, this paper presents a simple approach for estimating in real time the flash flood impacts at pan-European scale. The proposed method – named ReAFFINE – is designed to be integrated into an EWS for end-users operating over large spatial domains (e.g. across regions or countries). ReAFFINE uses the pan-European flash flood hazard estimates from the ERICHA system to retrieve the potentially flooded areas from the national flood maps (generated in the framework of the EU Floods Directive). By combining the potentially flooded areas with socio-economic exposure information, ReAFFINE estimates in real time the exposed population and critical infrastructures. For two catastrophic flash flood events affecting Europe in recent years, ReAFFINE has demonstrated the capability to identify impacts over large spatial scales. Also at sub-regional level, the method has mostly been able to locate the areas and municipalities where the most important impacts occurred. The results also show that the performance is sensitive to the quality of the rainfall estimates that drive the hazard estimation, and to the comprehensiveness of the employed flood maps.

Framework for climate proofing of flood risk management strategies in Finland

Climate change impacts have not previously been systematically considered in the selection and prioritisation of measures to manage flood risks in Finland. For the second flood risk management planning cycle according to the EU Floods Directive, we developed a framework for evaluating the adaptability of measures to expected changes in climate and land use. Our aim was to (1) provide regional data for flood risk managers and water resources planners, (2) develop a nationally consistent approach to identify the robustness of considered measures for a variety of conditions which (3) is applicable in both river basin management planning and flood risk management planning. According to the feedback from practitioners in regional flood management groups as well as planners, the framework helped to raise new thoughts and to open new perspectives in the planning process and may hence influence the practice of planning of flood risk reduction measures. Also, it was found useful to have access to regional, tailored data on hydrological impacts in the planning process and during communication with stakeholders. The described methodology has been used in the preparation of the 2nd version of flood risk management plans and for the 3rd version of river basin management plans. It is intended to use the same approach for next planning cycles.

GIS-Based Spatial and Multi-Criteria Assessment of Riverine Flood Potential: A Case Study of the Nitra River Basin, Slovakia

The aim of this study was to identify the areas with different levels of riverine flood potential (RFP) in the Nitra river basin, Slovakia, using multi-criteria evaluation (MCE)-analytical hierarchical process (AHP), geographic information systems (GIS), and seven flood conditioning factors. The RFP in the Nitra river basin had not yet been assessed through MCE-AHP. Therefore, the methodology used can be useful, especially in terms of the preliminary flood risk assessment required by the EU Floods Directive. The results showed that classification techniques of natural breaks (Jenks), equal interval, quantile, and geometric interval classified 32.03%, 29.90%, 41.84%, and 53.52% of the basin, respectively, into high and very high RFP while 87.38%, 87.38%, 96.21%, and 98.73% of flood validation events, respectively, corresponded to high and very high RFP. A single-parameter sensitivity analysis of factor weights was performed in order to derive the effective weights, which were used to calculate the revised riverine flood potential (RRFP). In general, the differences between the RFP and RRFP can be interpreted as an underestimation of the share of high and very high RFP as well as the share of flood events in these classes within the RFP assessment. Therefore, the RRFP is recommended for the assessment of riverine flood potential in the Nitra river basin.

A Comparative Study of the Effects of the 1872 Storm and Coastal Flood Risk Management in Denmark, Germany, and Sweden

From November 12th to 13th in 1872, an extreme coastal flood event occurred in the south Baltic Sea. An unusual combination of winds created a storm surge reaching up to 3.5 m above mean sea level, which is more than a meter higher than all other observations over the past 200 years. On the Danish, German, and Swedish coasts, about 300 people lost their lives. The consequences of the storm in Denmark and Germany were more severe than in Sweden, with significantly larger destruction and higher numbers of casualties. In Denmark and Germany, the 1872 storm has been more extensively documented and remembered and still influences local and regional risk awareness. A comparative study indicates that the collective memory of the 1872 storm is related to the background knowledge about floods, the damage extent, and the response to the storm. Flood marks and dikes help to remember the events. In general, coastal flood defence is to the largest degree implemented in the affected areas in Germany, followed by Denmark, and is almost absent in Sweden, corresponding to the extent of the collective memory of the 1872 storm. Within the affected countries, there is local variability of flood risk awareness associated with the collective memory of the storm. Also, the economic dependency on flood-prone areas and conflicting interests with the tourism industry have influence on flood protection decisions. The processes of climate change adaptation and implementation of the EU Floods Directive are slowly removing these differences in flood risk management approaches.

The ‘Flood Resilience Rose’: A management tool to promote transformation towards flood resilience

AbstractCoping with the growing impacts of flooding in EU countries, a paradigm shift in flood management can be observed, moving from safety‐based towards risk‐based approaches and holistic perspectives. Flood resilience is a common denominator of most of the approaches. In this article, we present the ‘Flood Resilience Rose’ (FRR), a management tool to promote harmonised action towards flood resilience in European regions and beyond. The FRR is a result of a two‐step process. First, based on scientific concepts as well as analysis of relevant policy documents, we identified three ‘levels of operation’. The first level refers to the EU Floods Directive and an extended multi‐layer safety approach, comprising the four different layers of protection, prevention, preparedness and recovery, and related measures to be taken. This level is not independent but depends both on the institutional (second level) and the wider (third level) context. Second, we used surveys, semi‐structured interviews and group discussions during workshops with experts from Belgium, Denmark, Germany, the Netherlands and the United Kingdom to validate the definitions and the FRR's practical relevance. The presented FRR is thus the result of rigorous theoretical and practical consideration and provides a tool capable to strengthen flood risk management practice.

A Flood Inundation Modeling Approach for Urban and Rural Areas in Lake and Large-Scale River Basins

Fluvial floods are one of the primary natural hazards to our society, and the associated flood risk should always be evaluated for present and future conditions. The European Union’s (EU) Floods Directive highlights the importance of flood mapping as a key stage for detecting vulnerable areas, assessing floods’ impacts, and identifying damages and compensation plans. The implementation of the EU Flood Directive in Greece is challenging because of its geophysical and climatic variability and diverse hydrologic and hydraulic conditions. This study addressed this challenge by modeling of design rainfall at the sub-watershed level and subsequent estimation of flood design hydrographs using the Natural Resources Conservation Service (NRCS) Unit Hydrograph Procedure. The HEC-RAS 2D model was used for flood routing, estimation of flood attributes (i.e., water depths and flow velocities), and mapping of inundated areas. The modeling approach was applied at two complex and ungauged representative basins: The Lake Pamvotida basin located in the Epirus Region of the wet Western Greece, and the Pinios River basin located in the Thessaly Region of the drier Central Greece, a basin with a complex dendritic hydrographic system, expanding to more than 1188 river-km. The proposed modeling approach aimed at better estimation and mapping of flood inundation areas including relative uncertainties and providing guidance to professionals and academics.

Issues of Natural Resources Law for Adopting Catchment-Based Measures for Flood Risk Management in Sweden

The EU Floods Directive calls for integrated flood risk management at a catchment scale. The potential of this directive to integrate relevant policy areas and deliver catchment-based measures may however be undermined by sectoral laws and policies in the Member States. This article focuses on the legal issues affecting the integration of catchment-based measures for managing flood risk in three relevant policy areas, namely, energy (in the form of hydropower production), agriculture, and forestry, in Sweden. The results show that that the present legal frameworks not only can restrict attempts to introduce catchment-based measures through compulsory means, but in some cases can also encumber collaborative and voluntary initiatives. It is therefore important to reinforce the catchment perspective in the processes leading to the adoption of flood risk management plans, in terms of assessing flood risks, evaluating measures and engaging stakeholders.

Comparison of multi-criteria-analytical hierarchy process and machine learning-boosted tree models for regional flood susceptibility mapping: a case study from Slovakia

Identification of areas susceptible to floods is an important issue which requires an increased attention due to the changing frequency and magnitude of floods, which is mainly a result of the ongoing climate change and increasing anthropic pressure on the landscape. In this study, the aim was to identify the areas susceptible to floods using and comparing two different approaches, namely the multi-criteria decision analysis-analytical hierarchy process (MCDA-AHP) and the machine learning-boosted classification (BCT) and boosted regression (BRT) tree. The study area was represented by the Topľa river basin, Slovakia. Altogether, seven relevant flood conditioning factors: elevation, slope, river network density, distance from river, flow accumulation, curve numbers and lithology as well as flood inventory database consisting of 107 flood locations were used. Based on the results, almost 40% of the study area is characterized by high to very high flood susceptibility using the MCDA-AHP. In case of the BCT and BRT models, the share of high and very high flood susceptibility class on the basin area is 45% and 38%, respectively. Validation of the performed flood susceptibility models confirmed generally higher accuracy of the machine learning models. The accuracy of the MCDA-AHP model was 81.33% while the accuracy of the boosted tree models was 87.70% and 91.42%, respectively, for classification and regression. The results of this study can enhance more effective preliminary flood risk assessment according to the EU Floods Directive.

GIS-based comparative assessment of flood susceptibility mapping using hybrid multi-criteria decision-making approach, naïve Bayes tree, bivariate statistics and logistic regression: A case of Topľa basin, Slovakia

Abstract Flood is a devastating natural hazard that may cause damage to the environment infrastructure, and society. Hence, identifying the susceptible areas to flood is an important task for every country to prevent such dangerous consequences. The present study developed a framework for identifying flood-prone areas of the Topľa river basin, Slovakia using geographic information system (GIS), multi-criteria decision making approach (MCDMA), bivariate statistics (Frequency Ratio (FR), Statistical Index (SI)) and machine learning (Naive Bayes Tree (NBT), Logistic Regression (LR)). To reach such a goal, different physical-geographical factors (criteria) were integrated and mapped. To access the relationship and interdependences among the criteria, decision-making trial and evaluation laboratory (DEMATEL) and analytic network process (ANP) were used. Based on the experts’ decisions, the DEMATEL-ANP model was used to compute the relative weights of different criteria and a GIS-based linear combination was performed to derive the susceptibility index. Separately, the flood susceptibility index computation through NBT-FR and NBT-SI hybrid models assumed, in the first stage, the estimation of the weight of each class/category of conditioning factor through SI and FR and the integration of these values in NBT algorithm. The application of LR stand-alone required the calculation of the weights of conditioning factors by analysing their spatial relation with the location of the historical flood events. The study revealed that very high and high flood susceptibility classes covered between 20% and 47% of the study area, respectively. The validation of results, using the past flood points, highlighted that the hybrid DEMATEL-ANP model was the most performant with an Area Under ROC curve higher than 0.97, an accuracy of 0.922 and a value of HSS of 0.844. The presented methodological approach used for the identification of flood susceptible areas can serve as an alternative for the updating of preliminary flood risk assessment based on the EU Floods Directive.