Open-Source Data Alternatives and Models for Flood Risk Management in Nepal

Water related natural hazards and climate change issues such as flood has become a serious threat to the lives, livelihoods and sustainable development of Bangladesh. Chilmari Upazila of Kurigram district which is one of the most seriously flood affected areas of Bangladesh has been taken as the study area. Bangladesh is already known as a role model for flood risk management around the world. But, the situation of flood management is not the same all around the country. The objectives of this study are to find out the main problems of the flood control and risk management system of Chilmari Upazila, and to develop a planning intervention guideline for its flood control and risk management. The interactive approach of the study involves participation of the stakeholders to develop local solutions to the flood problems. The empirical part of this study is conducted by household questionnaire survey and semi-structured in-depth interviews with questions regarding flood control and risk management. Main findings of the study state that the floods in Chilmari are managed in ad hoc manner. A coordinated and comprehensive management approach along with strong institutional framework is very important for sustainable flood control and risk management at Chilmari. Journal of Bangladesh Institute of Planners, Vol. 8, Dec 2015, pp. 111-121

Flood resilience is increasingly discussed in academia and practice as a complement to existing flood risk management approaches (Fekete, Hartmann, & Jüpner 2020). It is seen as a promising concept to deal with increasingly severe consequences of climate change in general, and with increasing flood risk in particular. The debate on flood resilience is linked to the paradigm shift from flood protection to risk management, which started in Europe after the major river flood events in 1993 and 1995 along the river Rhine (Hartmann, 2012), and has developed over the past decades—pushed by further major fluvial and pluvial flood events (Begum, Stive, & Hall, 2007; Hartmann & Juepner, 2014; Klijn, Samuels, & van Os, 2008; Patt & Jüpner, 2020). However, in flood risk management, the academic debate on resilience is only in its infancy (Jüpner et al., 2018; Vis, Klijn, Bruijn, & Buuren, 2003). Many different definitions exist (Disse, Johnson, Leandro, & Hartmann, 2020). Especially when it comes to specific implementation of resilience, the vagueness of the concept—which is sometimes described as one of its strengths (Baggio, Brown, & Hellebrandt, 2015; Brand & Jax, 2007)—can present a problem. How to design a resilient hydraulic infrastructure? This question has not only technical but also concerned with financial and legal aspects. This becomes more complicated when individual protection measures are put in a context of a larger system, such as a city or a region. When and how is a system such as a city or a region resilient, and how does one measure resilience? These questions are important, not only for construction but also for legal (such as liabilities), financial (budgetary), and political reasons. In other words, resilience is not (yet) a ready-to-use concept in flood risk management. Resilience challenges presumptions of traditional flood risk management in many ways. Resilience implies that more and different stakeholders and actors will be involved in flood risk management than before, such as landowners or spatial planners. Hitherto, flood risk management has been and still is mainly the domain of water management (Hartmann & Driessen, 2017), although the prevalence of the traditional civil engineering approach has been questioned before (van den Brink, 2009). This change is not positive for all actors—affected homeowners, but also city planners or mayors now must deal with questions that were previously outside of their realm of competence and responsibility. From a flood risk management perspective, many questions arise, such as: How does resilience add to and change the existing flood risk management system? How can resilience contribute to a more effective and efficient flood risk management approach? What are the specific advantages of integrating resilience in flood risk management? How can resilience be measured and quantified? Which parameters are most relevant? This special collection brings together contributions from different disciplines that address the specific challenges of implementing resilience in flood risk management. The special collection takes the European debate as a starting point. The European Floods Directive from 2007 (2007/EC/60) pushed the debate on flood risk management and resilience in Europe. This Directive established a legal frame on how countries in the European Union have to deal with flood risk for the first time (Hartmann & Jüpner, 2014). At the same time, the shift toward a risk-based approach raised questions such as "what can happen?" "what must not happen?" and "which security level can be realized at which costs?" Ultimately, flood risk management replaces the paradigm of complete protection against floods with the idea of managing the risk (Grünewald, 2005). This makes approaches to resilience and the reduction of damage potential (vulnerabilities)—not only for river floods but also for pluvial rainfall—important. The first three papers in this collection highlight the necessity and consequences of defining the concept of resilience. In their opinion paper, Fekete, Hartmann, and Jüpner (2020) point out that resilience is indeed a trend that neither can nor should be ignored in flood risk management, rather than it should be embraced—with a caveat: the concept is still not exactly defined and cannot be understood as a panacea for all shortcomings and challenges of flood risk management. So, is resilience merely a new buzzword? Dewulf et al. (2019) discuss the power and impact of defining resilience and therewith unravel the political-normative notion of flood resilience as a concept. This illustrates that, with flood resilience, flood risk management turns much more strongly towards social and political science than ever before. Discussing resilience and its definition is thus a crucial step toward successfully implementing it in flood risk management. In her advanced review, Rodina (2019) reveals different notions of resilience in different disciplines when taking on a broader view of the concept (i.e., not solely focusing on flood risks). She concludes that participation and stakeholder involvement are important components of resilience—a theme that is picked up in the next section of this special collection as well. So, though this article had not been part of the original set-up of the special collection, the conclusions are highly relevant for implementing flood resilience in flood risk management. Resilience requires more action by homeowners and citizens. All papers in this section of this special collection leave no doubt about that. Snel, Witte, Hartmann, and Geertman (2020), however, start with a very critical point of departure, namely that many publications on homeowner and citizen involvement do not seem to question if this involvement is necessary. The paper unravels the arguments that are prevalent in the academic debate for more involvement of homeowners in flood resilience, which supposedly comes along with a shift towards flood governance. Four types of main arguments are identified and discussed in the paper. Kuhlicke and the multidisciplinary team of authors writing on the behavioral turn in flood risk management (Kuhlicke et al., 2020) discuss in detail three underlying assumptions of increased involvement of citizens in flood risk management: the motivations of citizens, the effectiveness of measures, and capacities of citizens. In this vein, Rufat et al. (2020) discuss in their opinion paper need for a more nuanced debate on the link between flood risk perception and risk-mitigating behavior. Attems, Thaler, Genovese, and Fuchs (2020) then provide an overview of the measures that homeowners can take to enhance resilience by using property-level flood risk adaptation (PLFRA) measures. The paper confirms that such measures can indeed be an appropriate addition or complement to flood risk management. The third group of papers in this special collection addresses the issue of measuring and communicating resilience. The need for this comes not only from hydraulic engineering but also from the need to communicate about flood risk with homeowners and citizens, as they have to become more involved (as the earlier papers in this special collection clearly show). Pohl (2020) views resilience from a hydrological as well as a hydraulic engineering perspective and outlines what it means to include the concept in flood risk management. In particular, the contribution points out the difficulties of embedding resilience as a design criterion in hydraulic structures. Pohl concludes that—though the fuzziness of resilience is appreciated by some social scientists as a "boundary concept" (Baggio et al., 2015)—hydraulic engineering and hydrology inevitably require some quantifiable measurement of resilience. Fekete (2019) elaborates in his paper how cascading effects and critical infrastructure matter for flood resilience. It thereby shows how flood resilience with this perspective extends existing flood risk management approaches. Cascading effects of critical infrastructure can substantially affect the measurement of flood resilience. Schmitt and Scheid (2020) discuss the need for better risk communication and discuss approaches by focusing on pluvial floods. In particular, they show how a rainstorm severity index may supersede the communicative capacity of statistical rainfall parameters in the communication with nonexperts especially. In conclusion, the contributions in this special collection show how the concept of resilience is advancing flood risk management but also point out some crucial changes and challenges that flood resilience as a concept brings to the practical implementation of flood risk management. It seems inevitable that homeowners especially will play a much more fundamental role in flood resilience, which raises needs for measuring and communication of flood resilience. Along with this shift in flood risk management, the papers illustrate that flood resilience puts flood risk management in a hitherto unknown domain for many water managers, as flood resilience means embracing social and political science. Embedding flood resilience into flood risk management becomes a balancing act—on the one hand, resilience is a political and normative concept, but on the other hand, it needs to be implemented with concrete steps designed via civil engineering and hydrology. This tension is still unsolved and remains a dilemma in implementing flood resilience.

Despite an increasing number of people exposed to flood risks in Europe, flood risk perception remains low and effective flood risk management policies are rarely implemented. It becomes increasingly important to understand how local governments can design effective flood risk management policies to address flood risks. In this article, we study whether high flood exposure and flood risk perception correlate with the demand for a specific design of flood risk management policies. We take the ideal case of Switzerland and analyze flood risk management portfolios in 18 flood-prone municipalities along the Aare River. We introduce a novel combination of risk analysis and public policy data: we analyze correlations between recorded flood exposure data and survey data on flood risk perception and policy preferences for selected flood risk management measures. Our results indicate that local governments with high flood risk perception tend to prefer non-structural measures, such as spatial planning and ecological river restoration, to infrastructure measures. In contrast, flood exposure is neither linked to flood risk perception nor to policy preferences. We conclude that flood risk perception is key: it can decisively affect local governments’ preferences to implement specific diversified policy portfolios including more preventive or integrated flood risk management measures. These findings imply that local governments in flood-prone areas should invest in raising their population’s awareness capacity of flood risks and keep it high during periods without flooding.

Flood can be assessed through flood vulnerability, risk, and susceptibility analysis using remote sensing, geographic information system, and hydrological modelling. In this chapter, different stages, complexities, and processes of flood vulnerability, risk, and susceptibility assessment were discussed. The study reveals that flood vulnerability should be assessed based on four aspects: physical, social, economic, and environmental. Flood risk should be assessed by three stages: risk analysis, disaster relief, and preparedness, whereas flood susceptibility assessment involves three processes. Overall, it was found that the responsible factors vary as per the local conditions, which need to be carefully analyzed and selected. Furthermore, the role of remote sensing and geographic information system in flood risk management were found important especially in flood risk mapping and in the selection of responsible flooding factors.

For the purposes of preparing the national Disaster Risk Assessment, risk assessments are performed for twelve hazards. One of the hazards contained in the document is flood. For the flood hazard, it is necessary to collect data related to hydrography, historical floods, assumed areas of floods in the future, areas of potential flood risk assessment and others. Also, it is necessary to identify protected values in areas of potential flood risk assessment areas. In the process of flood risk management, data collection is performed in order to make a preliminary assessment of flood risks and flood hazard and flood risk maps. The aim of this paper is to propose a model for integrating data from the flood risk management into the disaster risk assessment, in order to increase the efficiency of flood prevention. The paper analyzes the type of data collected for the purpose of developing a documentation basis for flood risk management, which can be integrated into the national Disaster Risk Assessment in case of flood.

A Technical Assistance project funded by the European Investment Bank has been undertaken to develop a programme of flood risk management measures for Moldova that will address the main shortcomings in the present flood management system, and provide the basis for long-term improvement. Areas of significant flood risk were identified using national hydraulic and flood risk modelling, and flood hazard and flood risk maps were then prepared for these high risk areas. The flood risk was calculated using 12 indicators representing social, economic and environmental impacts of flooding. Indicator values were combined to provide overall estimates of flood risk. Strategic approaches to flood risk management were identified for each river basin using a multi-criteria analysis. Measures were then identified to achieve the strategic approaches. A programme of measures covering a 20-year period was developed together with a more detailed Short-Term Investment Plan covering the first seven years of the programme. Arrangements are now being made to implement the programme. The technical achievements of the project included national hydrological and hydraulic modelling covering 12,000 km of river, the development of 2-dimensional channel and floodplain hydraulic models from a range of topographic and bathymetric data, and an integrated flood risk assessment that takes account of both economic and non-monetary impacts.

PurposeFloods have been identified as the most frequent and threatening disaster in Sri Lanka amidst an increasing trend of natural and man-made disasters in the world. Subject experts state that disaster risk management should be based on the results of risk assessments, but flood risk management in Sri Lanka is seemingly not based on community-level flood risk assessments. Accordingly, the purpose of this paper is to introduce a community-level flood risk assessment method to the local context of Sri Lanka.Design/methodology/approachThe sample (n = 425) for the study was selected using the stratified random sampling method, and the Deduru Oya basin was selected as the study area. The risk assessment model introduced by Bollin et al. (2003) was used for the current study, but with some modifications. Accordingly, 16 variables were selected for the risk assessment. Descriptive data analysis methods were used in the study.FindingsCommunity-level flood risk assessment method was introduced. Variable index, flood risk index and flood risk map were developed for the study area. The Grama Niladari Divisions (GNDs) were grouped into five categories from very high risk to very low risk. The GNDs named Wirakumandaluwa, Thimbilla, Deduru Oya, Bangadeniya and Elivitiya were ranked as the most flood-risk GNDs, respectively.Originality/valueThis paper produces a flood risk assessment method for the local context. Flood risk in the study area was assessed based on people’s perceptions. Accordingly, the flood risk index and flood risk map for the study area were developed based on the empirical data. GNDs were ranked based on the flood risk index.

Understanding urbanization and its impact on flooding and flood risk is crucial to better manage flood risk in the future. This study analyzed land use/land cover changes and how urbanization would impact flooding and flood risk in Kathmandu Valley of Nepal, and assessed flood risk by integrating flood hazards based on hydrologic–hydraulic modeling with the Analytic Hierarchy Process-based Multi-Criteria Decision Analysis (AHP-MCDA) approach. Land cover maps for past years were generated using Landsat satellite images, and land use/land cover maps for future years were projected based on machine learning techniques. Flood simulations were conducted using a rainfall runoff inundation model with land cover maps for different flood scales to analyze the impact of urbanization and land cover changes on flood runoff, flood inundation extent, and flood inundation volume. Then, we comprehensively assessed flood risk by integrating hazard conditions simulated under different land cover conditions using a hydrologic–hydraulic model and the AHP-MCDA approach. The results showed that the flood inundation extent and the peak inundation volume for a 200-year flood may increase in the future by 10.66% and 15.04%, respectively, as a result of urbanization. The results also highlighted that urbanization may lead to an expansion of high-risk and very-high-risk areas in the future by 3.2% and 9.4%, respectively, indicating an increase in the valley’s flood vulnerability and greater severity of flood hazards.

Calibrating a High-Performance Hydrodynamic Model for Broad-Scale Flood Simulation: Application to Thames Estuary, London, UK

Risk governance is a widely used framework in natural and societal risk management research. Risks from natural hazards in urban areas call for the establishment of rigorous and participatory urban risk governance. In this study, we examined participatory risk governance (PRG) of flood risk management (FRM) in Seoul, South Korea. We conducted key informant interviews and implemented a survey with citizens, to explore perceptions of flood risks and risk management, and to examine prospects for improving PRG in Seoul. We found a gap between the perceptions of key informants and citizens. Key informants believed that citizens’ low awareness of flood risks hinders PRG. Yet our research found that citizens’ risk awareness was not low, and risk awareness may not be the main barrier to participation in PRG. Instead, we found that citizens lacked knowledge of FRM actions, and they assigned government bodies a high level of responsibility for FRM, compared to the level of responsibility that citizens assigned to themselves. Moreover, the actors involved in FRM tended not to trust each other, which implies a lack of mutual understanding. To increase the effectiveness of PRG, we suggest a polycentric governance structure anchored by a leading actor group, and active promotion of the participation of actors at multiple levels of governance. Communication between government and citizen participants, designed to foster improved understanding and recognition of one another’s roles and contributions to FRM, will enhance trust and improve the implementation of PRG in Seoul.

Current flood hazard mapping and risk management practices typically address pluvial and fluvial flooding separately. In many regions, however, compound pluvial and fluvial flooding (CPFF) are a significant challenge.  We develop a methodological approach to explore the relevance of CPFFs for the reconstruction processes and flood risk management in the Ahr valley in western Germany, devastated by the July 2021 flood. A non-stationary regional weather generator is applied to generate 100 realizations of synthetic precipitation and air temperature daily time series over a 72-year historical period (1950-2021). The method of fragments is used to disaggregate daily precipitation into hourly scale. The mHM hydrological model is used for rainfall-runoff simulation, producing the hourly discharge at the gauge Altenahr as fluvial boundary conditions for the downstream area. A total of 208 CPFF events are identified from 100 model realizations. The inundation depth and extent of these CPFF events are subsequently simulated using the RIM2D hydrodynamic model. We present a comparison of resulting CPFF flooding versus fluvial flooding alone. Our analysis reveals that fluvial flooding dominates maximum inundation depths, while pluvial rainfall expands the flood extent. Furthermore, CPFF events demonstrate substantially more severe hazards compared to fluvial flooding alone, which is typically the baseline for flood protection practices. These findings underscore the urgency of integrating CPFF into risk assessments and planning, offering policymakers critical insights to improve resilience against compound flood hazards.

The occurrence of flood disasters has become a vicious problem in many urban regions. Operationalization of flood resilience has become a significant concern with the increase of urban development and climate change. The objective of this paper is at first to analyze how flood resilience has been framed over the past period of time. Second, this paper has focused to identify the practical difficulties related to the available flood risk assessment and management frameworks for operationalization of flood resilience. The results show that the flood risk and resilience has been framed differently throughout the time, in diverse perspectives but still remains as contested concepts. Evolutionary resilience has been reframed the flood risk management system as an integrated and adaptive system with the recognition of the uncertainties due to the dynamics of socio-spatial interdependencies of flood risk. Therefore, the integration and the adaptive capacity of spatial planning has become a crucial aspect for operationalizing flood resilience which is governed through the knowledge base of the dominant discourses of stakeholders and the way of power and the resource exercised in the context.

With regard to minimizing flood damage, there are measures of different character each of which has its justification and plays an important role in flood protection. Implementation of traditional flood protection measures is still very important; however, an increasing role should be played particularly by flood prevention and flood risk management. The paper presents a case study on flood hazard and flood risk assessment at the local spatial scale using geographic information systems, remote sensing, and hydraulic modelling. As for determining flood hazard in the model area, which has 3.23 km2, the estimation of maximum flood discharges and hydraulic modelling were important steps. The results of one-dimensional hydraulic modelling, which are water depth and flow velocity rasters, were the basis for determining flood hazard and flood risk. In order to define flood risk, the following steps were applied: determining flood intensity on the basis of water depth and flow velocity rasters, determining flood hazard using three categories (low, medium, and high) based on flood intensity, defining vulnerability for the classes of functional areas using three categories of acceptable risk (low, medium, and high), and lastly determination of flood risk which represents a synthesis of flood hazard and vulnerability of the model area.

Since the European Parliament adopted its ‘Directive on the Assessment and Management of Flood Risks’, river basin and flood risk management plans have been subject to Strategic Environmental Assessment (SEA). This paper presents the landscape planning methods that were applied to support a flood risk management plan with SEA. It includes proposals for multifunctional flood management measures and the design and assessment of ‘Strategic Alternatives’ (STA). Every STA consists of sets of different measures that help manage floods effectively up to 100-year rainfall events. A GIS-based method was developed to enable flexible production and assessment of STA. 3D visualisations were also produced with GIS, and were mainly applied to support communication during stakeholder involvement. Results are discussed with reference to technical aspects and the importance of providing appropriate information to support decision-making. Theoretical considerations include discussions on landscape planning models and on the role of landscape planning within the new European planning system. Integrative qualities of landscape planning are highlighted, for example in designing new landscapes in cooperation with managers of flood risk. Future research direction includes landscape monitoring, and communicative landscape planning that contributes to strengthening democratic decision making on a regional scale.

Climate change, urbanization, and inadequate infrastructure exacerbate urban flood risks, yet one critical factor remains largely overlooked: hazardous debris such as cars, construction materials, wood, plastic containers among others. In the Valencia 2024 flood alone, the Spanish Insurance Compensation Consortium reported about 144,000 vehicles damaged or destroyed, many of them mobilized by the flow, which demonstrates the scale of large-debris impacts during floods. Debris alters and intensifies flooding impacts by clogging drainage systems and streets, decreasing flow conveyance, and causing direct damage to infrastructure, lives, and ecosystems. Nevertheless, debris dynamics are largely absent from flood risk assessments and management strategies. This Commentary highlights the urgent need to integrate debris considerations into urban flood planning and emergency response. Using case studies from recent catastrophic floods, we illustrate how debris amplifies hazard. We explore emerging scientific insights into the influence of debris in different flood types (flash, fluvial, coastal, tsunamis), and discuss why current management strategies fail to incorporate this factor. A solution-oriented roadmap is possible and we propose an actionable strategy toward the integration of debris into flood risk management, contributing to adapting cities toward higher levels of safety and resilience.