Integrated flood risk assessment in Iran: the role of development plans within a spatial planning perspective

ABSTRACTThe exclusive application of the engineering approach to flood defence is a matter of increasing disapproval. This has led to a new paradigm in flood management – the integrated management of flood risk. The change from engineering-based flood protection to the integrated management of flood risk is comparatively slow and has varied in different countries. In Slovakia, the engineering approach enjoys a strong tradition. Recently, the parliament and the government of the Slovak Republic (SR) approved documents which establish new legal and operational frameworks for flood defence in the SR. The aim of this paper is to analyse these documents regarding the concept of integrated flood risk management. The analysis shows that flood protection continues to be based on the traditional engineering approach, which reduces flooding by technical structures. How integrated flood risk assessment and management can eliminate the consequences of engineering flood management is presented through two approaches to preliminary flood risk assessment.

Integrated flood risk assessment of river basins: Application in the Dadu river basin, China

Floods are a widespread natural disaster with substantial economic implications and far-reaching consequences. In Northern Pakistan, the Hunza-Nagar valley faces vulnerability to floods, posing significant challenges to its sustainable development. This study aimed to evaluate flood risk in the region by employing a GIS-based Multi-Criteria Decision Analysis (MCDA) approach and big climate data records. By using a comprehensive flood risk assessment model, a flood hazard map was developed by considering nine influential factors: rainfall, regional temperature variation, distance to the river, elevation, slope, Normalized difference vegetation index (NDVI), Topographic wetness index (TWI), land use/land cover (LULC), curvature, and soil type. The analytical hierarchy process (AHP) analysis assigned weights to each factor and integrated with geospatial data using a GIS to generate flood risk maps, classifying hazard levels into five categories. The study assigned higher importance to rainfall, distance to the river, elevation, and slope compared to NDVI, TWI, LULC, curvature, and soil type. The weighted overlay flood risk map obtained from the reclassified maps of nine influencing factors identified 6% of the total area as very high, 36% as high, 41% as moderate, 16% as low, and 1% as very low flood risk. The accuracy of the flood risk model was demonstrated through the Receiver Operating Characteristics-Area Under the Curve (ROC-AUC) analysis, yielding a commendable prediction accuracy of 0.773. This MCDA approach offers an efficient and direct means of flood risk modeling, utilizing fundamental GIS data. The model serves as a valuable tool for decision-makers, enhancing flood risk awareness and providing vital insights for disaster management authorities in the Hunza-Nagar Valley. As future developments unfold, this study remains an indispensable resource for disaster preparedness and management in the Hunza-Nagar Valley region.

Integrated flood risk assessment is based on a multidimensional definition of flood risk, i.e. the extent of flood losses depends not only on the flood hazard itself, but also on the vulnerability of the social, economic, and environmental system to flooding. This study aims at the riverine flood risk mapping and assessment in municipalities of Slovakia. The riverine flood risk index (RFRI) was determined for 2,927 municipalities of Slovakia as a synthesis of the riverine flood hazard index (RFHI) and the riverine flood vulnerability index (RFVI) using the spatial multi-criteria analysis and geographic information systems (GIS). The RFHI was calculated based on eight indicators representing the riverine flood potential: number of flood events, slope, curvature, average annual maximum 5-day rainfall, river density, lithological rock types, soil texture, and land cover. Moreover, the RFVI was calculated based on seven indicators representing the social and economic vulnerability of municipalities: population density of urban areas of municipalities, share of population included in the age category 65+ from the total population of municipality, share of unemployed persons from the total number of economically active population in municipality, share of the Roma ethnicity from the total population of municipality, number of buildings within 100 m from a river, length of roads within 100 m from a river, and number of bridges in a municipality. The result of the Pearson correlation between individual indicators and the number of flood events in municipalities was used to determine the importance of indicators, which was subsequently used for assigning the indicator weights applying the rank sum method. The RFHI and RFVI for each municipality were calculated as the aggregation of the respective weighted indicators. The multiplication of the RFHI and RFVI resulted in the final RFRI. Based on the results obtained, the very high and high classes of RFHI contained 839 municipalities, which are located mostly in northern and eastern Slovakia and partly also in western and central Slovakia. The very high and high classes of RFVI included 817 municipalities, mainly, in northern and central Slovakia and partly also in western and eastern Slovakia. The highest RFRI values were recorded mostly by the municipalities in northern, central, and eastern Slovakia and partly also in western Slovakia. The very high and high risk of riverine flooding was recorded in 700 municipalities, i.e. these municipalities are included in the very high and high classes of RFRI. The results achieved in this study are useful, on one hand, for local self-governments and actors responsible for flood risk management, but more importantly for cyclic updating of the Preliminary Flood Risk Assessment in Slovakia under the EU Floods Directive. This work was supported by the VEGA agency under the grant number 1/0103/22 through the project entitled "Spatio-temporal Changes and Prediction of Flood Risk in Municipalities of Slovakia".

Urban flood risk assessment under rapid urbanization in Zhengzhou City, China

Despite traditional measures to prevent disasters, climate change and urbanization increase flood risk. Thus, flood resilience has attracted increased global concern. Understanding the commonalities and differences between flood resilience and risk is arguably important for flood risk reduction. However, these factors have been seldom reported in previous studies, and discussions on the role of flood resilience in flood risk analysis, assessment, and management are lacking. In this study, the association between flood resilience and risk is discussed using a case study in the Pearl River Delta. Flood resilience is quantified using a pressure-state-response (PSR) model, while flood risk is assessed based on the hazard-vulnerability framework and the extension catastrophe progression method. The implications of considering flood resilience in flood risk analysis, assessment, and management are proposed. The results suggest that the overall flood resilience (risk) in the study area is greater (lower) than that in the highly urbanized areas, and areas with low (high) flood resilience (risk) are mainly concentrated within the highly urbanized areas. Indices extracted from human society and highly related to human activities have the same attributes in both frameworks, while indices associated with climate and geography contribute to the two con- cepts differently. Flood resilience supplements the concept of flood risk, and can be incorporated into risk assessment as an index. Moreover, pre-disruption (post-disaster) measures should follow flood risk (resilience) assessment, and strategies that foster flood resilience should be included in flood risk management. This study provides references for flood resilience improvement and risk mitigation.

Towards flood risk reduction: Commonalities and differences between urban flood resilience and risk based on a case study in the Pearl River Delta

Extreme climatic events, such as floods, are becoming increasingly frequent and severe worldwide, including in Pakistan. The Swat River Catchment (SRC), located in the eastern Hindukush region of Pakistan, is highly susceptible to flooding due to its unique geographical and climatic conditions. However, despite the region’s susceptibility, comprehensive flood risk assessments that integrate hazard, vulnerability, and exposure components remain limited. To address this gap, this study assesses flood risk in the SRC using 22 indicators distributed across the three core dimensions of flood risk: hazard, vulnerability, and exposure. Flood hazard was modeled using 11 indicators, broadly categorized into environmental, hydrological, and geographical aspects, while vulnerability was evaluated through socio-economic factors, geographical proximity, and land use characteristics. Exposure was analyzed based on population metrics and critical infrastructure. All data were converted into thematic layers in GIS, systematically weighted using the Analytical Hierarchy Process (AHP) and combined to produce hazard, vulnerability, and exposure maps respectively. These maps were then integrated through a risk equation to generate the final flood risk map. The results reveal that 31% of the study area is in a high flood risk zone, 27% in moderate risk zones, 23% in low risk, and 19% are safe areas. The results were validated using the Area Under the Curve (AUC) technique, yielding a value of 0.92, which indicates high reliability. By presenting the first integrated flood risk assessment for the SRC, this study provides valuable insights into flood-prone areas and risk distribution. These results highlight the urgent need for enhanced flood risk management, especially in urban areas. The developed methodology serves as a valuable tool for disaster management authorities and planners, helping them make risk-informed decisions, allocate resources efficiently, and implement targeted flood mitigation strategies.

Due to the worldwide increasing threats of flooding as a consequence of climate change and the greater use by humans of natural floodplains, a change of paradigm from flood protection to integrated flood risk management (FRM) has taken place in Europe. This is reflected in the European Union (EU) Flood Directive and in the German Act to Improve Preventive Flood Control. In order to fulfill these new legal requirements following an integrated flood risk assessment, the application and results of water management tools need to be accessible during spatial planning processes. The effects of land use management may negatively influence the flood risk potential in a certain area. Therefore decision makers need to quantify the cause and consequences relationship of their design. The first part of this paper describes the derivation of flood risk, using hydrological and hydraulic models and the simple and understandable visualization of the results in flood risk maps. The second part of the paper uses this methodology and links the models and results directly into the land use planning process through a Decision Support System (DSS).

Floods driven by extreme precipitation events pose significant risks to communities, infrastructure, and ecosystems, particularly in regions with complex topography, such as Nepal. Probable Maximum Precipitation (PMP) is a critical parameter for assessing flood risk and designing resilient infrastructure. This review examines the methodologies and findings of a study focused on flood risk assessment in the West Rapti River Basin, Nepal, with emphasis on PMP and Probable Maximum Flood (PMF). This study employs hydrometeorological and statistical methods to estimate PMP, utilizes Snyder’s unit hydrograph for PMF calculation, and applies HEC-RAS 2D modeling to map flood hazards, vulnerabilities, and risks. Key findings include PMP estimates of 507 mm and 575 mm, a PMF of 11,211.1 m³/s, and detailed flood risk maps highlighting significant inundation risks in Deukhuri Valley. This review synthesizes the contributions of this study, compares its approaches to global practices, and discusses its implications for flood risk management in Nepal.The study on flood risk assessment in the West Rapti River Basin, Nepal, employs a comprehensive approach to evaluate and map flood hazards, vulnerabilities, and risks. By combining hydrometeorological and statistical methods to estimate Probable Maximum Precipitation (PMP), the research provides crucial insights into extreme precipitation events in the region. The use of Snyder's unit hydrograph for Probable Maximum Flood (PMF) calculation and HEC-RAS 2D modeling for flood hazard mapping demonstrates a robust methodology for assessing flood risks in complex topographical areas. The findings of this study have significant implications for flood risk management in Nepal and similar regions. The PMP estimates of 507 mm and 575 mm, along with the calculated PMF of 11,211.1 m³/s, provide valuable data for designing resilient infrastructure and implementing effective flood mitigation strategies. The detailed flood risk maps highlighting substantial inundation risks in Deukhuri Valley offer critical information for local authorities, urban planners, and policymakers to develop targeted interventions and improve community preparedness. This research contributes to the broader understanding of flood risk assessment methodologies and their application in regions with challenging topography, potentially informing similar studies in other flood-prone areas worldwide. Keywords: Flood risk assessment, West Rapti River Basin, Nepal, Probable Maximum Precipitation (PMP), Snyder's unit hydrograph, Probable Maximum Flood (PMF), HEC-RAS 2D modeling, Flood hazard mapping, Deukhuri Valley, Flood mitigation strategies, Hydrometeorological methods, Statistical analysis, Extreme precipitation events, Flood risk management, Inundation risks

This study is concerned with flood risk that can be assessed by integrating GIS, hydraulic modelling and required field information. A critical point in flood risk assessment is that while flood hazard is the same for a given area in terms of intensity, the risk could be different depending on a set of conditions (flood vulnerability). Clearly, risk is a function of hazard and vulnerability. This study aims to introducing a new approach of assessing flood risk, which successfully addresses this above-mentioned critical issue. The flood risk was assessed from flood hazard and vulnerability indices. Two-dimensional flood flow simulation was performed with Delft3D model to compute floodplain inundation depths for hazard assessment. For the purpose of flood vulnerability assessment, elements at risk and flood damage functions were identified and assessed, respectively. Then, finally flood risk was assessed first by combining replacement values assessed for the elements and then using the depth–damage function. Applying this approach, the study finds that areas with different levels of flood risk do not always increase with the increase in return period of flood. However, inundated areas with different levels of flood depth always increase with the increase in return period of flood. The approach for flood risk assessment adopted in this study successfully addresses the critical point in flood risk study, where flood risk can be varied even after there is no change in flood hazard intensity.

In this paper, a comprehensive flood hazard map for the vicinity of King Talal Dam in Jordan, utilizing advanced remote sensing (RS) and GIS methodologies, is developed. Key geographical and environmental factors, encompassing terrain slope, elevation, aspect, proximity to water streams, drainage density, and land use/land cover, are integrated to highlight areas with increased flood risk. This study, by employing a novel theoretical approach, harnesses the synergistic capabilities of RS and GIS to collect and analyze geospatial data. The Analytic Hierarchy Process (AHP) is applied to assign weights to various flood-conditioning factors, quantifying their relative importance in flood risk assessment. Through the weighted sum overlay technique, the aforementioned factors are integrated to categorize flood risk levels from very low to very high. This study successfully maps flood hazards, identifying areas near main water channels, ravines, and lower-elevation areas prone to flooding. This research provides a robust framework for flood risk assessment, contributing valuable knowledge to the fields of environmental management and disaster mitigation. It underscores the importance of continuous monitoring and updating of flood hazard maps to accommodate changing land use, climate, and hydrological conditions. The innovative application offers crucial insights for urban planners and policymakers, emphasizing the need for proactive strategies in flood-prone areas and serving as a model for similar geographical regions. Doi: 10.28991/CEJ-2024-010-05-05 Full Text: PDF

A comparative analysis on flood risk assessment and management performances between Beijing and Munich

With the environmental change and social development, the flood risk of urban watershed is a major issue in many countries. Integrated flood risk assessment will help aid decision making. However, integrated assessment is a complex problem which involves multiple factors and uncertainties. This paper has discussed the uncertainties and data fusion of multiple factors for integrated urban watershed flood risk assessment. First, the information fusion framework for integrated flood risk assessment and aggregation operator has been given. Then, uncertain categories are discussed, including aleatory uncertainty and epistemic uncertainty. The uncertainty handling methods are summarized. Finally, based on mixed aleatroy-epistemic uncertainty methods, a prototype of aggregation operator data fusion for urban flood risk assessment has been developed.

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.