Changes In Flood Risk Research Articles

Global warming induces significant changes in the fraction of stored precipitation in the surface soil

The fraction of stored precipitation (FSP) in surface soil is a new metric to characterize the synoptic-scale dynamics of wet soil moisture anomaly, the impact of which on the atmosphere differs from that of dry anomaly. Investigating the response of FSP to global warming is essential for understanding the land-atmosphere coupling and hydroclimate predictability in a changing climate. Here we use the Coupled Model Intercomparison Project phase 6 (CMIP6) models to project future changes in global FSP under two shared socioeconomic pathway (SSP) scenarios. The historical simulation based on Community Land Model version 5 (CLM5) during 1951–2014 suggests that 14.4% of the global land precipitation is remained in the surface soil within 3 days. The CLM5 simulated FSP applies to validate CMIP6 historical simulations in terms of global mean, spatial correlation and variability, and 5 among 12 CMIP6 models are finally selected to estimate FSP changes in a warming future. Compared with the FSP during the end of 20th century, it increases (decreases) significantly over 29% (16%) of the global land areas after 100 years in the business-as-usual scenario (SSP245). Global warming will increase FSP significantly over Amazon, most of Europe, western USA and Tibet Plateau, while the FSP decreases significantly over India and West Africa due to the increase of precipitation and soil moisture. The changes are more significant in the non-mitigation scenario (SSP585). The projected changes in FSP imply changes in regional flood risk and predictability in a warming future.

Dynamic risk of coastal flood and driving factors: Integrating local sea level rise and spatially explicit urban growth

Coastal flood risk facing urban communities is increasing due to the compound impacts of sea level rise (SLR) and urban growth. Accurate information on future dynamic risk of coastal flooding and its physical and socio-economic drivers is essential for planning effective and targeted adaptation. However, the current scenarios regarding urban development are insufficient to predict the future dynamic spatial distribution of urban socio-economic and physical growth, hindering the exact and dynamic assessment of future coastal flood risk. Moreover, the relative contributions of SLR and urban development to the future dynamics of city-level coastal flood risk have not been examined. Therefore, here we developed a land use-based urban growth scenario for the temporally and spatially explicit simulation of future urban growth in terms of buildings, roads and electrical facilities, and combined it with a local temporally explicit SLR scenario, into a “hazard-exposure-vulnerability” model, for the purpose of dynamic risk assessment of coastal flooding on the urban built environment in Xiamen, China by 2050, and accordingly examined the relative contributions of SLR and urban growth. Our results demonstrated a good performance of the land use-based urban growth model. SLR and urban growth will increase future coastal flood risk (represented by the expected annual damage, EAD) in varying degrees, but their combination is projected to exacerbate future flood damages significantly, indicating that considering either SLR or urban growth in isolation will underestimate future coastal flood risk. Moreover, the relative contributions of SLR and urban growth are dynamic over time, depending on the rate of SLR and the stage of urbanization: for example, the change in coastal flood risk is mainly attributable to urban growth in the phase of rapid urbanization before 2033 in Xiamen, yet the contribution of urban growth then becomes less important compared to SLR, when urbanization slows down, while SLR reaches a threshold after accelerating growth. The approach and results of our study can be considered a decision support tool, to help decision makers assess future coastal flood risk and detect the relative importance of each driving force, in order to employ land use planning, nature-based solutions and engineering protection, to achieve sustainable and resilient coastal cities.

An extremeness threshold determines the regional response of floods to changes in rainfall extremes

Precipitation extremes will increase in a warming climate, but the response of flood magnitudes to heavier precipitation events is less clear. Historically, there is little evidence for systematic increases in flood magnitude despite observed increases in precipitation extremes. Here we investigate how flood magnitudes change in response to warming, using a large initial-condition ensemble of simulations with a single climate model, coupled to a hydrological model. The model chain was applied to historical (1961–2000) and warmer future (2060–2099) climate conditions for 78 watersheds in hydrological Bavaria, a region comprising the headwater catchments of the Inn, Danube and Main River, thus representing an area of expressed hydrological heterogeneity. For the majority of the catchments, we identify a ‘return interval threshold’ in the relationship between precipitation and flood increases: at return intervals above this threshold, further increases in extreme precipitation frequency and magnitude clearly yield increased flood magnitudes; below the threshold, flood magnitude is modulated by land surface processes. We suggest that this threshold behaviour can reconcile climatological and hydrological perspectives on changing flood risk in a warming climate.

Flood Risk Assessment under Climate Change: The Petite Nation River Watershed

In Canada, climate change is expected to increase the extreme precipitation events by magnitude and frequency, leading to more intense and frequent river flooding. In this study, we attempt to map the flood hazard and damage under projected climate scenarios (2050 and 2080). The study was performed in the two most populated municipalities of the Petite Nation River Watershed, located in southern Quebec (Canada). The methodology follows a modelling approach, in which climate projections are derived from the Hydroclimatic Atlas of Southern Quebec following two representative concentration pathways (RCPs) scenarios, i.e., RCP 4.5 and RCP 8.5. These projections are used to predict future river flows. A frequency analysis was carried out with historical data of the peak flow (period 1969–2018) to derive different return periods (2, 20, and 100 years), which were then fed into the GARI tool (Gestion et Analyse du Risque d’Inondation). This tool is used to simulate flood hazard maps and to quantify future flood risk changes. Projected flood hazard (extent and depth) and damage maps were produced for the two municipalities under current and for future scenarios. The results indicate that the flood frequencies are expected to show a minor decrease in peak flows in the basin at the time horizons, 2050 and 2080. In addition, the depth and inundation areas will not significantly change for two time horizons, but instead show a minor decrease. Similarly, the projected flood damage changes in monetary losses are projected to decrease in the future. The results of this study allow one to identify present and future flood hazards and vulnerabilities, and should help decision-makers and the public to better understand the significance of climate change on flood risk in the Petite Nation River watershed.

Implications of measurement metrics on soil freezing curves: A simulation of freeze–thaw hysteresis

AbstractSoil freeze–thaw events have important implications for water resources, flood risk, land productivity, and climate change. A property of these phenomena is the relationship between unfrozen water content and sub‐freezing temperature, known as the soil freezing characteristic curve (SFC). It is documented that this relationship exhibits hysteretic behaviour when frozen soil thaws, leading to the definition of the soil thawing characteristic curve (STC). Although explanations have been given for SFC/STC hysteresis, the effect that ‘scale’ – particularly ‘measurement scale’ – may have on these curves has received little attention. The most commonly used measurement scale metric is the ‘support’, which is the spatial (or temporal) unit within which the measured variable is integrated or soil volume sampled. We show (a) measurement support can influence the range and shape of the SFC and (b) hysteresis can be attributed, in part, to the support and location of the measurements comprising the SFC/STC. We simulated lab measured temperature, volumetric water content (VWC), and permittivity from soil samples undergoing freeze–thaw transitions using Hydrus‐1D and a modified Dobson permittivity model. To assess the effect of measurement support and location on SFC/STC, we masked the simulated temperature and VWC/permittivity extent to match the instrument's support and location. By creating a detailed simulation of the intra‐ and inter‐support variability associated with the penetration of a freezing front, we demonstrate how measurement support and location can influence the temperature range over which water freezing events are captured. We show it is possible to simulate hysteresis in homogenous media with purely geometric considerations, suggesting that SFC/STC hysteresis may be more of an apparent phenomenon than mechanistically real. Lastly, we develop an understanding of how the location and support of soil temperature and VWC/permittivity measurements influence the temperature range over which water freezing events are captured.

Floods evolution in the Mediterranean region in a context of climate and environmental change

Floods are the most important risk in the Mediterranean region, both due to their frequency and impact. Studies of historical floods show flood-rich periods that could be associated with climate causes, but there is also a certain growing trend as a result of changes in land use and increased vulnerability. If climate scenarios point to an increase in the torrentiality of precipitation, with longer dry periods and more intense rainfall, there is still a high level of uncertainty in their impact in floods. This paper addresses this issue, also considering the complex role of changes to hazards, vulnerability, exposure and capacity. It presents a synthesis of the state of the art, with particular incidence in the first results of MedECC and the most recent bibliography on floods trend. Conclusions show that floods in this region are mainly consequence of flash-flood events. A common positive trend of flash floods in the past probably due to land use changes and the occupation of flood-prone areas has been found (high confidence). The increase of convective precipitation could also justify this positive trend in the most recent period, in some regions (low confidence). Vulnerabilities to water related hazards are expected to be influenced by the future socio-economic conditions at the regional scale (medium confidence). Although expected changes in flood risks are not univocal, nor evenly distributed, flood impacts will increase in the entire Mediterranean region, mainly as a consequence of global changes in the catchments (land use, vulnerability, exposure), joined in the Northern part of the basin to the increase of heavy rainfalls (medium confidence).

The 2019/2020 floods in the UK: a hydrological appraisal

The 2019/2020 floods in the <scp>UK</scp>: a hydrological appraisal

Chinese Built-up Land in Floodplains Moving Closer to Freshwaters

Human proximity to water and its dynamics are important to understanding the socio-hydrological dilemma between using floodplains and avoiding flood risk. However, previous studies have not distinguished between the water proximity of built-up land in floodplains (BLF) and the water proximity of built-up land outside floodplains (BLOF). This article provides a new and spatiotemporal perspective of the BLF water proximities for understanding the changing flood risk in China. The results show that China’s BLFs had an average water proximity of 5.41 km in 2014. Most of the BLFs (62%, 25.88×103 km2) were located within 3 km of waterbodies. From 1990 to 2014, China’s BLFs increased rapidly by 81% from 23.06×103 km2 to 41.74×103 km2, of which a large portion (57%) was concentrated in water surroundings (≤3 km), shortening the distance between BLFs and waterbodies by 169 m. The BLF growth concentrated in water surroundings even in areas where BLFs have an overall increasing distance from waterbodies. Both the increases in the BLFs and their proximity to waterbodies can increase flood exposure and exacerbate flood risk. The scientific community and policymakers should pay attention not only to the volume of BLF growth, but also its spatial relationship with waterbodies.

WebFRIS: An efficient web-based decision support tool to disseminate end-to-end risk information for flood management

The present study describes the development of a web-based flood risk information system ‘WebFRIS’ for Jagatsinghpur district, a severely flood-prone region in Eastern India. The WebFRIS is designed by using various readily available open-source web tools and packages such as Google Map, PHP, MySQL, and JSON. Special emphasis is directed towards designing the layout and architecture, to be easily accessible by any end-user irrespective of any technical know-how. The WebFRIS illustrates spatial maps of flood hazard, socio-economic vulnerability, and flood risk at the village level for two-time scenarios. While analyzing a set of graphical statistics depicting the changes in flood risk components, a significant increase in high and very-high categories of both flood hazard (~140%) and socio-economically vulnerable villages (~68%) is noticed during Scenario-I. The number of villages facing compound risk (contributed equally by flood hazard and socio-economic vulnerability) nearly doubled in Scenario-I. A spatial analysis of diametric changes in flood risk shows that a large proportion of villages in Balikuda, Ersama, and Tirtol tehsils have undergone radical changes. Following these observations, a set of possible engineering, social, and policy measures are proposed, whose implementation in the near future is expected to reinforce flood management in the study area. The WebFRIS architecture is flexible, easy-to-use; it is expected to provide crucial lessons to the local bodies, town-planners, water professionals, flood experts, and also the citizens, a precious knowledge on flood risk management. The WebFRIS may be considered as a precious cartographic product for environmental management. The proposed web platform is generic, as it can be applied to study other inter-related systems such as environmental protection, land-use planning, coastal habitat restoration, and community resilience building.Software and data availabilityName: Web Flood Risk Information System -WebFRISDeveloper: Indian Institute of Technology Bombay, MumbaiContact Information: (1) Mohit P. Mohanty: mohit2012.env@gmail.com; Environmental Science and Engineering Department, Indian Institute of Technology Bombay, India, and (2) Subhankar Karmakar: skarmakar@iitb.ac.in; Environmental Science and Engineering Department (http://www.esed.iitb.ac.in/), Indian Institute of Technology Bombay, India.Software(s) required: Internet browser (latest versions are recommended), and MIKE FLOOD 2018 or higher (https://www.mikepoweredbydhi.com/products/mike-flood).Programming languages: HTML, PhP, MySQL, JSONAvailability and cost: Any user can access WebFRIS for no cost at https://webfrisiitb.com/. The login credentials for entering WebFRIS are available with reasonable requests to the authors. The flood model set-up and input data are not available freely due to data confidentiality.

Tidal-flat reclamation aggravates potential risk from storm impacts

A better understanding of how tidal-flat reclamation changes the flood hazard is critical for climate-proofing coastal flood defense design of heavily urbanized areas. Since the 1950s, large-scale reclamation has been performed along the Shanghai coast, China, to fulfill the land demands of city expansion. We now show that the loss of tidal flats may have resulted in harmful impacts of coastal storm flooding. Using the foreshore profiles measured before and after reclamation (i.e., wide vs. narrow tidal flat), we determined the long-term changes in flood risk using a numerical model that combines extreme tidal level and wave overtopping analysis. Results show that wide tidal flats in front of a seawall provide efficient wave damping even during extreme water levels. Reclamation of these tidal flats substantially increased wave heights and correspondingly reduced the return period of a specific storm. As a result, estimates of overtopping are aggravated by more than 80% for the varying return periods examined. It is concluded that the disasters of coastal flooding after the 1997 tidal-flat reclamation in Hangzhou Bay, China are a consequence of both anthropogenic and natural activities. Moreover, our model calculations provide an equation describing the equivalent dike height needed to compensate for the loss of every km tidal flat of a certain elevation, and vice versa. For example, for every km of tidal flat ranging from high marsh to bare tidal flat that is being regained, the dike can be lowered by 0.84 m–0.67 m, when designing for a 1 in 200 years storm event. Overall, we suggest that wide tidal flats are ideally restored in front of dikes, and that when tidal areas are reclaimed, the seawall height is raised as part of the intertidal reclamation procedure. Using such an equivalent protection standard is relevant to designing hybrid flood defense system worldwide.

Spatial Planning for Urban Resilience in the Face of the Flood Risk: Institutional Actions, Opportunities and Challenges

The research was inspired by the increasing impact of extreme weather events and changing climate patterns on flood-prone regions and cities, and the consequent human and economic costs. Despite global efforts for flood resilience and climate adaptation involving climate analysts, economists, social scientists, politicians, hydrological engineers, spatial planners, and policymakers, it is only partially clear how best to construct resilience measures and implement concrete initiatives. The complexity of institutions is a key factor that is often neglected, and which needs further investigation. The thesis examines the institutional arrangements that determine the role of spatial planning in managing flood risk, through an in-depth case study of Guangzhou, one of the most vulnerable cities in China and globally. The thesis employs theories of historical institutionalism, planning procedure and planning tools, policy framing and collaborative governance, to explore the mechanisms and factors that influence the creative planning and design process. Content analysis, GIS-based mapping, stakeholder analysis and TOWS analysis are used to investigate data from official policy documents, grey literature, geo-information data and interview scripts. The findings indicate that institutional arrangements, such as long-established planning traditions, formal planning procedures and tools, policy framing patterns and contextual organisational factors, determine spatial planning’s role in managing flood risk. They do this through (1) the extent of the changeability of an established planning system towards expanded flood resilience measures; (2) the performance of cross-level communication and boundary-spanning work between planning and water management; (3) the legal framework that planners and hydrological engineers follow; and (4) the capacities of planning and water management institutions to work on flood issues. This research shows how to apply knowledge from policy science, political science, institutional science and administration, to analyse the nature of the planning process in tackling the urgent challenge of flood risk and climate change.

Impact of compound flood event on coastal critical infrastructures considering current and future climate

Abstract. The changing climate and anthropogenic activities raise the likelihood of damage due to compound flood hazards, triggered by the combined occurrence of extreme precipitation and storm surge during high tides and exacerbated by sea-level rise (SLR). Risk estimates associated with these extreme event scenarios are expected to be significantly higher than estimates derived from a standard evaluation of individual hazards. In this study, we present case studies of compound flood hazards affecting critical infrastructure (CI) in coastal Connecticut (USA). We based the analysis on actual and synthetic (considering future climate conditions for atmospheric forcing, sea-level rise, and forecasted hurricane tracks) hurricane events, represented by heavy precipitation and surge combined with tides and SLR conditions. We used the Hydrologic Engineering Center's River Analysis System (HEC-RAS), a two-dimensional hydrodynamic model, to simulate the combined coastal and riverine flooding of selected CI sites. We forced a distributed hydrological model (CREST-SVAS) with weather analysis data from the Weather Research and Forecasting (WRF) model for the synthetic events and from the National Land Data Assimilation System (NLDAS) for the actual events, to derive the upstream boundary condition (flood wave) of HEC-RAS. We extracted coastal tide and surge time series for each event from the National Oceanic and Atmospheric Administration (NOAA) to use as the downstream boundary condition of HEC-RAS. The significant outcome of this study represents the evaluation of changes in flood risk for the CI sites for the various compound scenarios (under current and future climate conditions). This approach offers an estimate of the potential impact of compound hazards relative to the 100-year flood maps produced by the Federal Emergency Management Agency (FEMA), which is vital to developing mitigation strategies. In a broader sense, this study provides a framework for assessing the risk factors of our modern infrastructure located in vulnerable coastal areas throughout the world.

Urbanization impacts on flood risks based on urban growth data and coupled flood models

Urbanization increases regional impervious surface area, which generally reduces hydrologic response time and therefore increases flood risk. The objective of this work is to investigate the sensitivities of urban flooding to urban land growth through simulation of flood flows under different urbanization conditions and during different flooding stages. A sub-watershed in Toronto, Canada, with urban land conversion was selected as a test site for this study. In order to investigate the effects of urbanization on changes in urban flood risk, land use maps from six different years (1966, 1971, 1976, 1981, 1986, and 2000) and of six simulated land use scenarios (0%, 20%, 40%, 60, 80%, and 100% impervious surface area percentages) were input into coupled hydrologic and hydraulic models. The results show that urbanization creates higher surface runoff and river discharge rates and shortened times to achieve the peak runoff and discharge. Areas influenced by flash flood and floodplain increases due to urbanization are related not only to overall impervious surface area percentage but also to the spatial distribution of impervious surface coverage. With similar average impervious surface area percentage, land use with spatial variation may aggravate flash flood conditions more intensely compared to spatially uniform land use distribution.

Extreme sea level variability dominates coastal flood risk changes at decadal time scales

Coastal flood risk assessments typically ignore interannual to multidecadal variability stemming from mean sea level, storm surges, and long period tides (i.e. 4.4 year perigean and 18.6 year nodal cycles), although combined these can lead to significant variations in extreme sea levels (ESL). Here, we examine the effects of ESL variability on the amplification of flood frequencies and risks for 17 major U.S. coastal cities. We also quantify the relative importance of ESL variability compared to long-term relative sea level rise (RSLR). Results show that, depending on the region, observed ESL variability can lead to amplification factors of up to 79, indicating that the 100 year return period event can become a 1.26 year event during certain time periods when ESL variability peaks high. Additionally, depending on the RSLR scenario considered, the observed range of ESL variability is equivalent to the RSLR projected to occur over the next few years in some locations and several decades (up to 2100) in others. These ESL fluctuations also modulate flood risk estimates, with the aggregated 100 year flood losses for the 17 major U.S. coastal cities changing by up to US$ 141 979 million (or 28%). This study demonstrates the importance of including ESL variability in regional coastal flood risk assessments; it highlights the importance of being aware and vigilant of these variations when observed and projected ESL situations are quantified assuming that certain sea level components are stationary.

Spatial Planning for Urban Resilience in the Face of the Flood Risk

The research was inspired by the increasing impact of extreme weather events and changing climate patterns on flood-prone regions and cities, and the consequent human and economic costs. Despite global efforts for flood resilience and climate adaptation involving climate analysts, economists, social scientists, politicians, hydrological engineers, spatial planners, and policymakers, it is only partially clear how best to construct resilience measures and implement concrete initiatives. The complexity of institutions is a key factor that is often neglected, and which needs further investigation. The thesis examines the institutional arrangements that determine the role of spatial planning in managing flood risk, through an in-depth case study of Guangzhou, one of the most vulnerable cities in China and globally. The thesis employs theories of historical institutionalism, planning procedure and planning tools, policy framing and collaborative governance, to explore the mechanisms and factors that influence the creative planning and design process. Content analysis, GIS-based mapping, stakeholder analysis and TOWS analysis are used to investigate data from official policy documents, grey literature, geo-information data and interview scripts. The findings indicate that institutional arrangements, such as long-established planning traditions, formal planning procedures and tools, policy framing patterns and contextual organisational factors, determine spatial planning’s role in managing flood risk. They do this through (1) the extent of the changeability of an established planning system towards expanded flood resilience measures; (2) the performance of cross-level communication and boundary-spanning work between planning and water management; (3) the legal framework that planners and hydrological engineers follow; and (4) the capacities of planning and water management institutions to work on flood issues. This research shows how to apply knowledge from policy science, political science, institutional science and administration, to analyse the nature of the planning process in tackling the urgent challenge of flood risk and climate change.

Spatial Planning for Urban Resilience in the Face of the Flood Risk

The research was inspired by the increasing impact of extreme weather events and changing climate patterns on flood-prone regions and cities, and the consequent human and economic costs. Despite global efforts for flood resilience and climate adaptation involving climate analysts, economists, social scientists, politicians, hydrological engineers, spatial planners, and policymakers, it is only partially clear how best to construct resilience measures and implement concrete initiatives. The complexity of institutions is a key factor that is often neglected, and which needs further investigation. The thesis examines the institutional arrangements that determine the role of spatial planning in managing flood risk, through an in-depth case study of Guangzhou, one of the most vulnerable cities in China and globally. The thesis employs theories of historical institutionalism, planning procedure and planning tools, policy framing and collaborative governance, to explore the mechanisms and factors that influence the creative planning and design process. Content analysis, GIS-based mapping, stakeholder analysis and TOWS analysis are used to investigate data from official policy documents, grey literature, geo-information data and interview scripts. The findings indicate that institutional arrangements, such as long-established planning traditions, formal planning procedures and tools, policy framing patterns and contextual organisational factors, determine spatial planning’s role in managing flood risk. They do this through (1) the extent of the changeability of an established planning system towards expanded flood resilience measures; (2) the performance of cross-level communication and boundary-spanning work between planning and water management; (3) the legal framework that planners and hydrological engineers follow; and (4) the capacities of planning and water management institutions to work on flood issues. This research shows how to apply knowledge from policy science, political science, institutional science and administration, to analyse the nature of the planning process in tackling the urgent challenge of flood risk and climate change.

Impact of Historical Channel Deepening on Tidal Hydraulics in the Delaware Estuary

AbstractAnthropogenic modifications of estuarine morphology such as navigational channels have changed tidal dynamics in many estuaries. The implications of deepening may include shifts in tidal range, sediment transport, pollutant dispersal, and changes in flood risk, among others. Here, we use a numerical model to study how channel deepening has altered tidal elevation, currents, and energy fluxes in the Delaware, a convergent estuary on the east coast of the United States. Historical (1848) and modern (2014) depth soundings were digitized and gridded for a numerical model of the estuary. Numerical experiments indicate a doubling in tidal range, shifts in the arrival time of high water, and changes in elevation‐velocity phase. A historical increase in the upstream conveyance and transmission of energy is consistent with bigger amplitudes, swifter currents, and more progressive wave dynamics in the navigational channel. Changes in local topography were key in the modulation of tidal energy transmission upstream, especially in the tidal river.

Probabilistic Quantification in the Analysis of Flood Risks in Cross-Border Areas of Poland and Germany

Measuring the probability of flood risk is a key issue in the economics of natural disasters. This discipline studies actual and potential effects of natural disasters on the functioning of economic systems. In traditional economic understanding, it is assumed that both the decision making processes and market processes operate within a certain level of access to information. It is also assumed that the effects of certain phenomena are predictable. However, a natural disaster is difficult to predict. It is hard to predict the time of its occurrence, its impact, direct exposure to its effects and finally, its social and economic results. Exposure to a random hazard, combined with the amount of damage resulting from its potential materialization, is called risk. In this study, the authors focus on presenting a method for quantification of the random element of flood risk. We are using measurement data for cross-border areas between Poland and Germany who witnessed a flood of the century in the 1990s. The empirical data illustrate the usefulness and universality of probabilistic quantification methods for flood risk analysis. The analysis of water level is interesting in a much broader context than the hydrological-economic one. In Central Europe, river water level is immediately connected with two other disaster-like phenomena: drought and heavy rainfall. Also, the course of the Oder river is typical for North European Plain. Therefore, the conclusions presented by the authors are universal by nature and describe certain broader phenomena. Employment of methods of probabilistic quantification using extreme values yields very interesting results: flood risk changes dynamically. Five-year period measurements themselves indicate that there are periods of relatively low exposure of the areas to the disaster (with negligible probability 0.02) and periods of disproportionately high risk increase. The risk of exceeding alarm levels and warning levels changes rapidly, reaching as much as 30% in some locations.

The flood risk changes effective factors in Tehran Metropolis

The flood risk changes effective factors in Tehran Metropolis

Regional Inequalities in Flood Insurance Affordability and Uptake under Climate Change

Flood insurance coverage can enhance financial resilience of households to changing flood risk caused by climate change. However, income inequalities imply that not all households can afford flood insurance. The uptake of flood insurance in voluntary markets may decline when flood risk increases as a result of climate change. This increase in flood risk may cause substantially higher risk-based insurance premiums, reduce the willingness to purchase flood insurance, and worsen problems with the unaffordability of coverage for low-income households. A socio-economic tipping-point can occur when the functioning of a formal flood insurance system is hampered by diminishing demand for coverage. In this study, we examine whether such a tipping-point can occur in Europe for current flood insurance systems under different trends in future flood risk caused by climate and socio-economic change. This analysis gives insights into regional inequalities concerning the ability to continue to use flood insurance as an instrument to adapt to changing flood risk. For this study, we adapt the “Dynamic Integrated Flood and Insurance” (DIFI) model by integrating new flood risk simulations in the model that enable examining impacts from various scenarios of climate and socio-economic change on flood insurance premiums and consumer demand. Our results show rising unaffordability and declining demand for flood insurance across scenarios towards 2080. Under a high climate change scenario, simulations show the occurrence of a socio-economic tipping-point in several regions, where insurance uptake almost disappears. A tipping-point and related inequalities in the ability to use flood insurance as an adaptation instrument can be mitigated by introducing reforms of flood insurance arrangements.