Sustainable Flood Risk Research Articles

Flood Susceptibility and Risk Mapping of Kathmandu Valley Watershed, Nepal

Comprehensive flood risk assessment is often constrained by a lack of appropriate data in high-altitude watersheds, particularly in developing countries like Nepal, where institutional capacities are limited for mapping and monitoring flood-prone communities. This study, one of the first of its kind, produced spatial multi-criteria-based flood susceptibility, vulnerability, and risk index maps for the Kathmandu Valley (KV) watershed in Nepal using an Analytical Hierarchy Process (AHP) approach and Geographical Information System (GIS). The result shows that most parts of the KV (around 80%) have moderate to low flood susceptibility around the watershed but susceptibility is prominent in southern areas. Highly flood-susceptible regions (about 14%) are found mainly along the riverbanks. Flood vulnerability, primarily influenced by population density and literacy rate, is moderate to low in most areas of the watershed (around 86%), predominantly higher in the central urban areas, and gradually lower towards the edge of the watershed. Flood risks in the major portion of the watershed (around 72%), mainly in the southern and eastern parts, are estimated as moderate to low risk, whereas higher risk zones are found in the central urban areas. The high contrast in flood vulnerability scores across the watershed has mainly contributed to the variation of flood risk zones, as flood susceptibility scores are fairly distributed over the watershed. The study findings will help policymakers develop location-specific sustainable flood risk management strategies for the flood-vulnerable communities in the KV watershed.

Public policies on sustainable flood risk management: Study cases of the Netherlands and Malawi

Background: This study compares flood management strategies in Malawi and the Netherlands, emphasizing their respective advantages and disadvantages. The Netherlands is renowned globally for its flood defense, prioritizing prevention, stakeholder involvement, and nature-based solutions through sophisticated infrastructure and proactive approaches. However, future challenges may arise from economic expansion and climate change pressures. In contrast, Malawi, despite having fewer resources, is making strides with its National Resilience Strategy, focusing on risk mitigation, sustainable agriculture, and early warning systems to combat flooding and hunger vulnerabilities. Yet, it faces significant issues with financing, management, and the long-term sustainability of community-based projects. Methods: This study utilized bibliometric analysis and a Systematic Literature Review (SLR), employing a comparative approach to evaluate Malawian and Dutch public policies on flooding disasters. The aim was to identify similarities and differences in their approaches to flood risk management. Findings: The Netherlands’ proactive flood management strategy, characterized by advanced infrastructure and integrated policy frameworks, is a model for high-capacity settings. Its emphasis on nature-based solutions and stakeholder engagement further strengthens its resilience. Malawi's approach, while resource-constrained, shows promise through its National Resilience Strategy, which targets risk reduction, sustainable agricultural practices, and robust early warning systems. Nevertheless, Malawi continues to grapple with financing, effective management, and the sustainability of its flood risk mitigation initiatives. Conclusion: The experiences of the Netherlands and Malawi illustrate the need for continuous policy adaptation and the challenges of managing flood risks in diverse socioeconomic contexts. This research clarifies the relative benefits of different flood control strategies and emphasizes the importance of tailored approaches to address the complexities of flood dangers. Both countries demonstrate the ongoing need for regulatory reform to enhance flood risk mitigation efforts. Novelty/Originality of this Study: This study uniquely compares the flood risk management policies of Malawi and the Netherlands, highlighting the differences between a developing nation's reactive, community-focused approach and a developed country's proactive, infrastructure-intensive strategy. By analyzing their respective strengths and weaknesses, it identifies potential improvements and opportunities for both nations to enhance their flood management and resilience.

Building a Resilient City through Sustainable Flood Risk Management: The Flood-Prone Area of Phra Nakhon Sri Ayutthaya, Thailand

Building a Resilient City through Sustainable Flood Risk Management: The Flood-Prone Area of Phra Nakhon Sri Ayutthaya, Thailand

Participatory Framework for Urban Pluvial Flood Modeling in the Digital Twin Era

The recent advancement in digital twin technology, which creates virtual replicas of real-world processes, offers an interactive testbed for understanding and predicting environmental changes. As pluvial flood damage escalates globally in urban areas, there remains a gap in understanding the most effective collaboration between governments and local residents for sustainable flood risk management. To address this gap, we develop a participatory framework for urban pluvial flood modeling, incorporating open source software, virtual reality, minimum viable product, and gamification components. This framework engages citizens in every phase of the participatory modeling process, from input data preparation, through hydrological model construction, to model verification, and experiments. We present a case study on the recurring pluvial flood damages in South Korea's Gangnam region, demonstrating the practical implications of an interactive, web-based crowdsourcing platform to leverage community engagement and local knowledge. The results underscore the evidence of a proactive role for citizens, not merely as recipients of disaster information but as key contributors collaborating with a range of stakeholders in stormwater management and modeling. Combining digital twin technology with citizen participation can empower informed decision-making and collective actions in the evolving digital era, leading to a disaster-resilient community.

Identifying the Contributing Sources of Uncertainties in Urban Flood Vulnerability in South Korea Considering Multiple GCMs, SSPs, Weight Determination Methods, and MCDM Techniques

This study quantified uncertainties involved in assessing the future flood vulnerability in 33 urban areas with population exceeding designated thresholds in South Korea. The driver-pressure-state-impact-response (DPSIR) framework was utilized as the study procedure, integrating social, economic, and environmental factors. In addition, a total of 220 cases of combinations were examined, encompassing twenty general circulation models combined with shared socioeconomic pathway scenarios, five weight determination methods, and three multi-criteria decision-making (MCDM) techniques, as sources of inherent uncertainties in the process. The rankings of urban flood vulnerability (UFV) for the selected cities were comprehensively assessed considering all combinations, followed by an analysis of variance test to investigate contributing sources of uncertainties. As a result, Incheon and Busan were found to be vulnerable to flooding, while Yeongcheon and Andong appeared to be safe cities. Some cities exhibited wide ranges in their rankings, such as Daegu, Yangpyeon, and Jeongeup. The identified contributing sources were weighting (58%), MCDM (27%), and the combination of weighting and MCDM methods together (15%). This study revealed that weight determination methods and MCDM techniques are the primary sources of uncertainties in the assessment of future UFV instead of multiple GCMs and SSPs. This finding underscores the importance for decision-makers and stakeholders to carefully consider these uncertainties for sustainable flood risk management and prevention.

A policy instruments palette for spatial quality: lessons from Dutch flood risk management

ABSTRACT Worldwide, more integrated and spatially embedded forms of flood risk management have been advocated. In the Netherlands, this ‘spatial turn’ can be associated with a quest for spatial quality, i.e. making use of existing landscape values to create more liveable, aesthetic and sustainable flood risk management solutions. Reflecting on Dutch flood risk management practice, this paper inventorizes which policy instruments are currently used to strengthen spatial quality, and how involved actors view these instruments. We present empirical insights on common concerns, standpoints and dilemmas from the Dutch Flood Protection Programme (DFPP), a large-scale reinforcement operation to climate-proof the Netherlands’ main flood defences by 2050. Spatial quality here remains a rather ambiguous policy objective, lacking a legally binding framework. Using the NATO-policy instruments’ typology as a starting point, and based on a co-learning process between science and practice, we present an instruments palette that can be used to strengthen spatial quality in flood risk management. Our findings reveal that the DFPP makes use of rather ‘soft’ policy instruments. The actual achievement of spatial quality goals seems to depend largely on the combined project team competencies, guidance and support provided by responsible water authorities, and commitment of other project partners.

Economic assessment of nature-based solutions to reduce flood risk and enhance co-benefits

Flooding is expected to increase due to climate change, urbanisation, and land use change. To address this issue, Nature-Based Solutions (NBSs) are often adopted as innovative and sustainable flood risk management methods. Besides the flood risk reduction benefits, NBSs offer co-benefits for the environment and society. However, these co-benefits are rarely considered in flood risk management due to the inherent complexities of incorporating them into economic assessments. This research addresses this gap by developing a comprehensive methodology that integrates the monetary analysis of co-benefits with flood risk reduction in economic assessments. In doing so, it aspires to provide a more holistic view of the impact of NBS in flood risk management. The assessment employs a framework based on life-cycle cost-benefit analysis, offering a systematic and transparent assessment of both costs and benefits over time supported by key indicators like net present value and benefit cost ratio. The methodology has been applied to the Tamnava basin in Serbia, where significant flooding occurred in 2014 and 2020. The methodology offers valuable insights for practitioners, researchers, and planners seeking to assess the co-benefits of NBS and integrate them into economic assessments. The results show that when considering flood risk reduction alone, all considered measures have higher costs than the benefits derived from avoiding flood damage. However, when incorporating co-benefits, several NBS have a net positive economic impact, including afforestation/reforestation and retention ponds with cost-benefit ratios of 3.5 and 5.6 respectively. This suggests that incorporating co-benefits into economic assessments can significantly increase the overall economic efficiency and viability of NBS.

Urban flood hazard assessment in Awka metropolis using multi-criteria decision process

Urban flooding is an escalating global threat, and Awka Metropolis in Anambra state Nigeria is no exception. The city's rapid urbanization and inadequate infrastructure have left it increasingly vulnerable to flooding, exacerbated by the impacts of climate change. Anticipated flood effects include disruption of daily life, infrastructure damage, and threats to public safety, necessitating urgent attention. This study presents a comprehensive assessment of urban flood hazards in Awka Metropolis, utilizing an integrated approach combining the Analytical Hierarchy Process (AHP) and Flood Hazard Index (FHI) to gauge the city's flood vulnerability. The primary objectives were to identify key geophysical factors contributing to flooding, categorize these factors by their vulnerability, determine their reliability indices, delineate flood-prone zones, and generate a spatial flood extent map. The methodology encompassed data acquisition, pre-processing, Flood Modeling (evaluating slope, Elevation, Drainage Network, and flow accumulation), the application of Analytical Hierarchy Process, and the utilization of the Flood Hazard Index. The results classified Awka Metropolis into three flood risk zones: high (837.84 hectares, 14.70%), moderate (2182.65 hectares, 38.30%), and low (2678.45 hectares, 46.99%). These findings provide indispensable insights into the distribution of flood hazards across the city, enabling urban planners and authorities to strategically allocate resources, prioritize mitigation initiatives, and formulate targeted flood risk reduction strategies. Importantly, the incorporation of stakeholder input enhances the study's practical relevance and applicability in real-world urban planning and disaster management scenarios. In conclusion, this research offers a robust and multidimensional framework for assessing urban flood hazards in Awka Metropolis. The synergy of the Analytical Hierarchy Process and Flood Hazard Index equips urban planners, policymakers, and disaster management agencies to proactively tackle the mounting urban flooding challenges. The study's outcomes contribute to the development of sustainable flood risk reduction measures, ultimately enhancing the resilience of Awka Metropolis to future flood events.

Urban development and long-term flood risk and resilience: Experiences over time and across cultures. Cases from Asia, North America, Europe and Australia

Rivers are the lifeblood of many cities, but flood risk is projected to increase due to urbanisation and climate change. Better floodplain management in and near urban areas is required to produce the New Urban Agenda’s ‘just, safe, healthy, accessible, affordable, resilient and sustainable cities’. Many jurisdictions are looking to move or keep people out of human-constructed residential ‘niches’ on hazardous floodplains, but this has proved difficult to achieve. Our historical case studies of colonial societies in ancient Rome, as well as on the Yangtze, Mississippi and Brisbane rivers, show the deep roots of many contemporary flood risk issues, such as failures of risk perception related to recent settlement, the moral hazard of spending on flood defence infrastructure, the creeping nature of floodplain encroachment into ‘niches’ of perceived protection created by structural interventions, the need for a central, ‘whole of river’ approach, and the difficulties of implementing this approach locally. These case studies also suggest solutions, including the adoption of Indigenous perspectives, benefits to incentivise local actors and a historical education strategy to increase appetite for more sustainable flood risk mitigation.

IMPACT OF LAND USE ACTIVITIES ON THE HYDROLOGICAL REGIME IN THE JUNJUNG RIVER BASIN, PENANG ISLAND, MALAYSIA

Land use activities in the river basin have a very significant negative impact on the hydrological regime, especially surface runoff. The study of the impact of land use activities on the hydrological regime in the Junjung river basin aims to analyse changes in the rate of surface runoff due to current land use changes and land use planning in 2030. To achieve the goal of this study, curve number analysis was used as a determinant of hydrological parameters in the development of HEC HMS modelling in the study basin area. The results of the study found that the current land use in 2020 recorded an average curve number value of 85.77 and then increased to 86.36 in 2030 due to land use changes in 2030. The change in the value of the curve number has had an impact on the hydrological regime that is surface runoff because there is an increase in the percentage of impervious areas from 22.84 percent in 2020 to 31.14 percent by 2030. The rate of change in runoff is shown through the simulation of the peak flow rate that occurs according to the frequency of the event, which is between 0.7 to 4.9 percent. The results obtained from this study can be used as fundamental data for advanced studies of flood control and management for better sustainable flood risk management.

Flooding and Waste Disposal Practices of Urban Residents in Nigeria

The rising incidence of flooding is a cause for global concern. Flooding is caused by both natural and human factors. In Nigeria, flooding has been attributed chiefly to human factors, such as poor waste disposal practices and management. Despite this known link, no empirical study is known to have engaged with urban residents to understand their actual waste disposal practices and ascertain their knowledge of the connection of their waste disposal practices to the flooding they are increasingly experiencing. This work fills this gap via an in-depth engagement with residents and experts on their waste disposal practices in the flood-prone city of Port Harcourt via a mixed-methods case study. Questionnaire surveys and qualitative interviews served as the primary data collection tools. The study confirms the poor waste practices of residents and provides empirical data on the prevalence of various forms of waste disposal practices. This provides key information that can guide the needed change in waste practices to eliminate this known flood driver in the pursuit of sustainable flood risk management. This is pertinent as waste management is one of the areas where citizens have agency to act. A behavioural shift is needed in this regard and must be encouraged via targeted public sensitization. Having local vanguards champion waste management behavioural turn is also recommended. The relevant authorities are encouraged to adopt a more sustainable approach to waste management by ensuring there are waste services and putting in place adequate disincentives to deter offenders.

Adapting drainage networks to the urban development: An assessment of different integrated approach alternatives for a sustainable flood risk mitigation in Northern Italy

Political bodies, planners and the scientific community agree on the need for making cities and communities resilient and sustainable in the near future. Urban infrastructures generate too often negative impacts on the surrounding environment. Hence, it is considered today an absolute priority implementing actions able to generate an optimal relationship between citizens and the environment. Even in the field of hydraulic constructions and urban hydrology, it is therefore essential to develop water management strategies able to contribute to the definition of this new paradigm of city. With regard to flood management, integrated strategies including the combined implementation of Stormwater Detention Tanks and Sustainable Drainage Strategies (SuDS) seem successful solutions but additional studies are required to define their potential. This research aims at assessing and comparing different integrated drainage alternatives involving the single or combined implementation of two categories of SuDS in Sesto Ulteriano (Northern Italy): Green Infrastructures (GI) and flood control areas. The Hydraulic Risk Mitigation Index (HRMI), is here proposed to account for different hydraulic parameters in the performance assessment of an integrated drainage strategy. Results highlighted the importance of HRMI as decision support measure and the effectiveness of SuDS strategies, especially those involving GI, at reducing urban flooding.

Particle swarm optimization based LSTM networks for water level forecasting: A case study on Bangladesh river network

Floods are one of the most catastrophic natural disasters. Water level forecasting is an essential method of avoiding floods and disaster preparedness. In recent years, models for predicting water levels have been developed using artificial intelligence techniques like the artificial neural network (ANN). It has been demonstrated that more advanced and sequenced-based deep learning techniques, like long short-term memory (LSTM) networks, are superior at forecasting hydrological data. However, historically, most LSTM hyperparameters were based on experience, which typically did not produce the best outcomes. The Particle Swarm Optimization (PSO) method was utilized to adjust the LSTM hyperparameter to increase the capacity to learn data sequence characteristics. Utilizing water level observation data from stations along Bangladesh's Brahmaputra, Ganges, and Meghna rivers, the model was utilized to estimate flood dynamics. The Nash Sutcliffe efficiency (NSE) coefficient, root mean square error (RMSE), and MAE were used to assess the model's performance, where PSO-LSTM model outperforms the ANN, PSO-ANN, and LSTM models in predicting water levels in all stations. The PSO-LSTM model provides improved prediction accuracy and stability and improves water level forecasting accuracy at varying lead times. The findings may aid in sustainable flood risk mitigation in the study region in the future.

Natural flood management: Opportunities to implement nature‐based solutions on privately owned land

AbstractThe implementation of Natural Flood Management (NFM), as an example of a nature‐based solution (NbS), is promoted as a risk reduction strategy to support sustainable flood risk management and climate change adaptation more widely. Additionally, as an NbS, NFM aims to provide further multiple benefits, such as increased biodiversity and improved water quality as well as improved mental health. The implementation of NbS often needs private‐owned or managed land, yet can create conflicts between the different stakeholders which can undermine the social consensus required for successful implementation. Consequently, a main question is how the multiple benefits and requirements of NFM can be delivered to meet the different goals of the wide variety of stakeholders who must be involved. This article discusses the challenges and potential of implementing NFM as an alternative to the traditional technical mitigation measures in flood risk management. We outline four opportunities in the implementation of NFM: physical conditions of the catchment, social interaction, financial resources, and institutional setting. Their importance is then demonstrated and compared to different examples across the globe. Nevertheless, the core drivers reflect the social interaction and institutional setting and the role of stakeholders in the successful implementation of NFM.This article is categorized under:Engineering Water > Planning WaterHuman Water > Water GovernanceScience of Water > Water ExtremesWater and Life > Conservation, Management, and Awareness

Preliminary Study on Flood Simulation using the HEC-HMS Model for Muda River, Malaysia

Flooding poses a severe threat to human beings and causes significant damage to property, infrastructure, and agricultural production. The flood also has severe consequences for socio-economic activities and can lead to the loss of human life. One of the significant factors that cause the flood is rapid development, especially in the floodplain area. This study estimates the flood discharge along the Muda River, Malaysia using Hydrological Modelling System (HEC-HMS). The finding shows that the HEC-HMS model performed well during the validation period, in which the coefficient determination (R2) between observed and simulated discharge during the validation process ranges from 0.51-0.84. In terms of design flood, the model simulated the peak flow with 1247-1448.8 m3/s and 1798.5-3662.5 m3/s for 50 and 100-year ARIs, respectively. The results obtained from this study can be used as fundamental data for advanced studies of flood control and management for better sustainable flood risk management.

Understanding Flood Vulnerability in Local Communities of Kogi State, Nigeria, Using an Index-Based Approach

In West Africa, the impacts of flooding are becoming more severe with climate warming. Flood-prone communities in Kogi State in north-central Nigeria are affected by annual flooding and some extreme flood events. The negative impacts remain a major obstacle to development, environmental sustainability, and human security, exacerbating poverty in the region. Reducing and managing the impacts of flooding are increasingly becoming a challenge for individual households. Analysing vulnerability to flooding (a function of exposure, susceptibility, and lack of resilience) and identifying its causes using an index-based approach to achieve sustainable flood risk management were the focus of this study. A semi-structured questionnaire was used to collect relevant data from 400 households in 20 purposively selected communities. Based on expert opinions and an extensive literature review, 16 sets of relevant indicators were developed. These indicators were normalised and aggregated to compute the flood vulnerability index (FVI) for each community. This was then used to compare, classify, and rank communities in terms of their vulnerability to flooding. The results of the study showed that the selected communities were at varying levels of the risk of flooding. Four of the communities including the Onyedega, Ogba Ojubo, Odogwu, and Ichala Edeke communities were found to have very high vulnerability to flooding compared to others. Several factors such as poor building structures, lack of evacuation and flood management measures, over-dependence of households on agriculture, lack of diversification of economic activities, and weak household economic capacity were identified as causes. These findings are useful for developing flood risk reduction and adaptation strategies, such as ecosystem-based approaches, to reduce current and future vulnerability to flooding in Nigeria and other developing countries with similar conditions.

Comparison of sustainable flood risk management by four countries – the United Kingdom, the Netherlands, the United States, and Japan – and the implications for Asian coastal megacities

Abstract. Sustainable flood risk management (SFRM) has become popular since the 1980s. Many governmental and non-governmental organisations have been keen on implementing the SFRM strategies by integrating social, ecological, and economic themes into their flood risk management (FRM) practices. However, the justifications for SFRM are still somewhat embryonic, and it is not yet clear whether this concept is influencing current policies in different countries. This paper reviews the past and current flood management experiences from flood defence to SFRM in four developed countries to highlight lessons for coastal megacities in development. The paper explores recent strategies such as “Making Space for Water”, Planning Policy Statement 25 (PPS25), and the National Planning Policy Framework (NPPF) in the UK and “Room for the River” in the Netherlands, which were implemented to mitigate flooding, integrate FRM with sustainability concepts, and deliver sound FRM practice for future generations. In this context, the United States has also established a National Flood Insurance Program (NFIP), and in a different approach, Japan has developed an advanced flood warning and evacuation contingency system to prepare for climatic extremes. These case studies give good lessons in achieving long-term SFRM to deliver sound flood management practices considering socio-economic and environmental concerns. Most developing coastal megacities especially in Asia are still heavily reliant on a traditional hard-engineering approach, which may not be enough to mitigate substantial risks due to human factors (e.g. large population, rapid socio-economic growth, subsidence from excessive groundwater extraction) and natural factors (e.g. climate change including sea-level rise and land subsidence). It is clear that different countries and cities have their interpretation of SFRM, but this paper explores how policymakers can adopt “mixed options” to move towards long-term thinking about sustainability with social, economic, and environmental considerations.

Sustainable flood risk assessment using deep learning-based algorithms with a blockchain technology

The couplings of convolutional neural networks (CNN) with random forest (RF), support vector machine (SVM), long short-term memory (LSTM), and extreme gradient boosting (XGBoost) ensemble algorithms were used to construct novel ensemble computational models (CNN-LSTM, CNN-XG, CNN-SVM, and CNN-RF) for flood hazard mapping in the monsoon-dominated catchment, Bangladesh. The results revealed that geology, elevation, the normalized difference vegetation index (NDVI), and rainfall are the most significant parameters in flash floods based on the Pearson correlation technique. Statistical method such as the area under the curve (AUC) was used to evaluate model performance. The CNN-RF model could be a promising tool for precisely predicting and mapping flash floods as it is outperformed the other models (AUC = 1.0). Furthermore, to meet sustainable development goals (SDGs), a blockchain-based technology is proposed to create a decentralized flood management tool for help seekers and help providers during and post floods. The suggested tool accelerates emergency rescue operations during flood events.

Performance of an environmentally‐aligned, low maintenance flood alleviation scheme on the Burn of Mosset, Forres, Scotland

AbstractFlooding of the town of Forres, Scotland prompted the implementation of a flood alleviation scheme (FAS) featuring a low earth‐fill dam constructed upstream of the town to create a flood retention area, limiting peak discharges entering the urban area. Flow through the dam is controlled by a weir, and it was recognised that if coarse sediment, large wood, and/or debris collected at the weir this could adversely affect its performance. To ensure reliable operation of the weir, the “Burn Management Works” (BMW) were designed to reconnect the embanked, elevated river channel to its floodplain, naturally retaining coarse sediment, large wood, and debris upstream of the dam. The FAS became operational on August 28, 2009 and impounded floodwater for the first time just 1 week later. Here, we report the results of monitoring of the BMW performed between 2011 and 2018. We find that the BMW have fulfilled their primary, flood alleviation functions by retaining large amounts of sediment and large wood without the need for maintenance. In so doing, the BMW has evolved from the single‐thread, trapezoidal, pilot channel constructed through the initially dry pasture, to the shifting mosaic of anastomosed channels, ponds, wetlands, and scrublands that now comprise the fully‐connected floodplain. In parallel, local interest groups have transformed this flood defence asset into a bird and wildlife area that is enjoyed by the community. Lessons learned from the BMW can inform other projects seeking to use nature‐based solutions to deliver sustainable flood risk management while simultaneously achieving goals for river restoration and community engagement.

A comparative flood damage and risk impact assessment of land use changes

Abstract. Sustainable flood risk management encompasses the implementation of nature-based solutions to mitigate flood risk. These measures include the establishment of land use types with a high (e.g., forest patches) or low (e.g., sealed surfaces) water retention and infiltration capacity at strategic locations in the catchment. This paper presents an approach for assessing the relative impact of such land use changes on economic flood damages and associated risk. This spatially explicit approach integrates a reference situation, a flood damage model, and a rainfall-runoff model considering runoff re-infiltration and propagation to determine relative flood risk mitigation or increment related to the implementation of land use change scenarios. The applicability of the framework is illustrated for a 4800 ha undulating catchment in the region of Flanders, Belgium, by assessing the afforestation of 187.5 ha (3.9 %), located mainly in the valleys, and sealing of 187.5 ha, situated mainly at higher elevations. These scenarios result in a risk reduction of 57 % (EUR 100 000) for the afforestation scenario and a risk increment of <1 % (EUR ∼ 500) for the sealing scenario.