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1.	Beven, Keith, et al. (författare) Epistemic uncertainties and natural hazard risk assessment - Part 1 : A review of different natural hazard areas 2018 Ingår i: Natural hazards and earth system sciences. - : COPERNICUS GESELLSCHAFT MBH. - 1561-8633 .- 1684-9981. ; 18:10, s. 2741-2768 Forskningsöversikt (refereegranskat)abstract This paper discusses how epistemic uncertainties are currently considered in the most widely occurring natural hazard areas, including floods, landslides and debris flows, dam safety, droughts, earthquakes, tsunamis, volcanic ash clouds and pyroclastic flows, and wind storms. Our aim is to provide an overview of the types of epistemic uncertainty in the analysis of these natural hazards and to discuss how they have been treated so far to bring out some commonalities and differences. The breadth of our study makes it difficult to go into great detail on each aspect covered here; hence the focus lies on providing an overview and on citing key literature. We find that in current probabilistic approaches to the problem, uncertainties are all too often treated as if, at some fundamental level, they are aleatory in nature. This can be a tempting choice when knowledge of more complex structures is difficult to determine but not acknowledging the epistemic nature of many sources of uncertainty will compromise any risk analysis. We do not imply that probabilistic uncertainty estimation necessarily ignores the epistemic nature of uncertainties in natural hazards; expert elicitation for example can be set within a probabilistic framework to do just that. However, we suggest that the use of simple aleatory distributional models, common in current practice, will underestimate the potential variability in assessing hazards, consequences, and risks. A commonality across all approaches is that every analysis is necessarily conditional on the assumptions made about the nature of the sources of epistemic uncertainty. It is therefore important to record the assumptions made and to evaluate their impact on the uncertainty estimate. Additional guidelines for good practice based on this review are suggested in the companion paper (Part 2).
2.	Beven, Keith, et al. (författare) Epistemic uncertainties and natural hazard risk assessment - Part 2 : What should constitute good practice? 2018 Ingår i: Natural hazards and earth system sciences. - : COPERNICUS GESELLSCHAFT MBH. - 1561-8633 .- 1684-9981. ; 18:10, s. 2769-2783 Tidskriftsartikel (refereegranskat)abstract Part 1 of this paper has discussed the uncertainties arising from gaps in knowledge or limited understanding of the processes involved in different natural hazard areas. Such deficits may include uncertainties about frequencies, process representations, parameters, present and future boundary conditions, consequences and impacts, and the meaning of observations in evaluating simulation models. These are the epistemic uncertainties that can be difficult to constrain, especially in terms of event or scenario probabilities, even as elicited probabilities rationalized on the basis of expert judgements. This paper reviews the issues raised by trying to quantify the effects of epistemic uncertainties. Such scientific uncertainties might have significant influence on decisions made, say, for risk management, so it is important to examine the sensitivity of such decisions to different feasible sets of assumptions, to communicate the meaning of associated uncertainty estimates, and to provide an audit trail for the analysis. A conceptual framework for good practice in dealing with epistemic uncertainties is outlined and the implications of applying the principles to natural hazard assessments are discussed. Six stages are recognized, with recommendations at each stage as follows: (1) framing the analysis, preferably with input from potential users; (2) evaluating the available data for epistemic uncertainties, especially when they might lead to inconsistencies; (3) eliciting information on sources of uncertainty from experts; (4) defining a workflow that will give reliable and accurate results; (5) assessing robustness to uncertainty, including the impact on any decisions that are dependent on the analysis; and (6) communicating the findings and meaning of the analysis to potential users, stakeholders, and decision makers. Visualizations are helpful in conveying the nature of the uncertainty outputs, while recognizing that the deeper epistemic uncertainties might not be readily amenable to visualizations.
3.	Blauhut, Veit, et al. (författare) Lessons from the 2018-2019 European droughts : a collective need for unifying drought risk management 2022 Ingår i: Natural hazards and earth system sciences. - : Copernicus Publications. - 1561-8633 .- 1684-9981. ; 22:6, s. 2201-2217 Tidskriftsartikel (refereegranskat)abstract Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazard severity and frequency of past drought events have been studied in detail, little is known about the effect of drought management strategies on the actual impacts and how the hazard is perceived by relevant stakeholders. In a continental study, we characterised and assessed the impacts and the perceptions of two recent drought events (2018 and 2019) in Europe and examined the relationship between management strategies and drought perception, hazard, and impact. The study was based on a pan-European survey involving national representatives from 28 countries and relevant stakeholders responding to a standard questionnaire. The survey focused on collecting information on stakeholders' perceptions of drought, impacts on water resources and beyond, water availability, and current drought management strategies on national and regional scales. The survey results were compared with the actual drought hazard information registered by the European Drought Observatory (EDO) for 2018 and 2019. The results highlighted high diversity in drought perception across different countries and in values of the implemented drought management strategies to alleviate impacts by increasing national and sub-national awareness and resilience. The study identifies an urgent need to further reduce drought impacts by constructing and implementing a European macro-level drought governance approach, such as a directive, which would strengthen national drought management and mitigate damage to human and natural assets.
4.	Blauhut, Veit, et al. (författare) Lessons from the 2018–2019 European droughts: A collective need for unifying drought risk management 2021 Ingår i: Natural hazards and earth system sciences. - : Copernicus Publications. - 1561-8633 .- 1684-9981. Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract Drought events and their impacts vary spatially and temporally due to diverse pedo-climatic and hydrologic conditions, as well as variations in exposure and vulnerability, such as demographics and response actions. While hazardous severity and frequency of past drought events have been studied in detail, little is known about the effect of drought management strategies on the actual impacts, and how the hazard is perceived by relevant stakeholders for inducing action. In a continental study, we characterised and assessed the impacts and the perceptions of two recent drought events (2018 and 2019) in Europe and examined the relationship between management strategies and drought perception, hazard and impacts. The study was based on a pan-European survey involving national representatives from 28 countries and relevant stakeholders responding to a standard questionnaire. The survey focused on collecting information on stakeholders’ perceptions of drought, impacts on water resources and beyond, water availability and current drought management strategies at national and regional scales. The survey results were compared with the actual drought hazard information registered by the European Drought Observatory (EDO) for 2018 and 2019. The results highlighted high diversity in drought perceptions across different countries and in values of implemented drought management strategies to alleviate impacts by increasing national and sub-national awareness and resilience. The study concludes with an urgent need to further reduce drought impacts by constructing and implementing a European macro-level drought governance approach, such as a directive, which would strengthen national drought management and lessen harm to human and natural potentials.
5.	Buchecker, M., et al. (författare) The role of risk perception in making flood risk management more effective 2013 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 13, s. 3013-3030 Tidskriftsartikel (refereegranskat)abstract Over the last few decades, Europe has suffered from a number of severe flood events and, as a result, there has been a growing interest in probing alternative approaches to managing flood risk via prevention measures. A literature review reveals that, although in the last decades risk evaluation has been recognized as key element of risk management, and risk assessment methodologies (including risk analysis and evaluation) have been improved by including social, economic, cultural, historical and political conditions, the theoretical schemes are not yet applied in practice. One main reason for this shortcoming is that risk perception literature is mainly of universal and theoretical nature and cannot provide the necessary details to implement a comprehensive risk evaluation. This paper therefore aims to explore a procedure that allows the inclusion of stakeholders' perceptions of prevention measures in risk assessment. It proposes to adopt methods of risk communication (both one-way and two-way communication) in risk assessment with the final aim of making flood risk management more effective. The proposed procedure not only focuses on the effect of discursive risk communication on risk perception, and on achieving a shared assessment of the prevention alternatives, but also considers the effects of the communication process on perceived uncertainties, accepted risk levels, and trust in the managing institutions.The effectiveness of this combined procedure has been studied and illustrated using the example of the participatory flood prevention assessment process on the Sihl River in Zurich, Switzerland. The main findings of the case study suggest that the proposed procedure performed well, but that it needs some adaptations for it to be applicable in different contexts and to allow a (semi-) quantitative estimation of risk perception to be used as an indicator of adaptive capacity.
6.	Canedo-Rosso, Claudia, et al. (författare) Drought impact in the Bolivian Altiplano agriculture associated with the El Niño-Southern Oscillation using satellite imagery data 2021 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 21:3, s. 995-1010 Tidskriftsartikel (refereegranskat)abstract Drought is a major natural hazard in the Bolivian Altiplano that causes large agricultural losses. However, the drought effect on agriculture varies largely on a local scale due to diverse factors such as climatological and hydrological conditions, sensitivity of crop yield to water stress, and crop phenological stage among others. To improve the knowledge of drought impact on agriculture, this study aims to classify drought severity using vegetation and land surface temperature data, analyse the relationship between drought and climate anomalies, and examine the spatiooral variability of drought using vegetation and climate data. Empirical data for drought assessment purposes in this area are scarce and spatially unevenly distributed. Due to these limitations we used vegetation, land surface temperature (LST), precipitation derived from satellite imagery, and gridded air temperature data products. Initially, we tested the performance of satellite precipitation and gridded air temperature data on a local level. Then, the normalized difference vegetation index (NDVI) and LST were used to classify drought events associated with past El Niño-Southern Oscillation (ENSO) phases. It was found that the most severe drought events generally occur during a positive ENSO phase (El Niño years). In addition, we found that a decrease in vegetation is mainly driven by low precipitation and high temperature, and we identified areas where agricultural losses will be most pronounced under such conditions. The results show that droughts can be monitored using satellite imagery data when ground data are scarce or of poor data quality. The results can be especially beneficial for emergency response operations and for enabling a proactive approach to disaster risk management against droughts.
7.	Darmawan, Herlan, et al. (författare) Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption 2018 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 18:12, s. 3267-3281 Tidskriftsartikel (refereegranskat)abstract Lava domes are subjected to structural weakening that can lead to gravitational collapse and produce pyroclastic flows that may travel up to several kilometers from a volcano's summit. At Merapi volcano, Indonesia, pyroclastic flows are a major hazard, frequently causing high numbers of casualties. After the Volcanic Explosivity Index 4 eruption in 2010, a new lava dome developed on Merapi volcano and was structurally destabilized by six steam-driven explosions between 2012 and 2014. Previous studies revealed that the explosions produced elongated open fissures and a delineated block in the southern dome sector. Here, we investigated the geomorphology, structures, thermal fingerprint, alteration mapping and hazard potential of the Merapi lava dome by using drone-based geomorphologic data and forward-looking thermal infrared images The block on the southern dome of Merapi is delineated by a horseshoe-shaped structure with a maximum depth of 8 m and it is located on the unbuttressed southern steep flank. We identify intense thermal, fumarole and hydrothermal alteration activities along this horseshoe-shaped structure. We conjecture that hydrothermal alteration may weaken the horseshoe-shaped structure, which then may develop into a failure plane that can lead to gravitational collapse. To test this instability hypothesis, we calculated the factor of safety and ran a numerical model of block-and-ash flow using Titan2D. Results of the factor of safety analysis confirm that intense rainfall events may reduce the internal friction and thus gradually destabilize the dome. The titan2D model suggests that a hypothetical gravitational collapse of the delineated unstable dome sector may travel southward for up to 4 km. This study highlights the relevance of gradual structural weakening of lava domes, which can influence the development fumaroles and hydrothermal alteration activities of cooling lava domes for years after initial emplacement.
8.	Depietri, Yaella, et al. (författare) Multi-hazard risks in New York City 2018 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 18:12, s. 3363-3381 Tidskriftsartikel (refereegranskat)abstract Megacities are predominantly concentrated along coastlines, making them exposed to a diverse mix of natural hazards. The assessment of climatic hazard risk to cities rarely has captured the multiple interactions that occur in complex urban systems. We present an improved method for urban multi-hazard risk assessment. We then analyze the risk of New York City as a case study to apply enhanced methods for multi-hazard risk assessment given the history of exposure to multiple types of natural hazards which overlap spatially and, in some cases, temporally in this coastal megacity. Our aim is to identify hotspots of multi-hazard risk to support the prioritization of adaptation strategies that can address multiple sources of risk to urban residents. We used socioeconomic indicators to assess vulnerabilities and risks to three climate-related hazards (i.e., heat waves, inland flooding and coastal flooding) at high spatial resolution. The analysis incorporates local experts' opinions to identify sources of multi-hazard risk and to weight indicators used in the multi-hazard risk assessment. Results demonstrate the application of multi-hazard risk assessment to a coastal megacity and show that spatial hotspots of multi-hazard risk affect similar local residential communities along the coastlines. Analyses suggest that New York City should prioritize adaptation in coastal zones and consider possible synergies and/or trade-offs to maximize impacts of adaptation and resilience interventions in the spatially overlapping areas at risk of impacts from multiple hazards.
9.	Di Baldassarre, Giuliano, et al. (författare) Brief communication : Comparing hydrological and hydrogeomorphic paradigms for global flood hazard mapping 2020 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 20:5, s. 1415-1419 Tidskriftsartikel (refereegranskat)abstract Global floodplain mapping has rapidly progressed over the past few years. Different methods have been proposed to identify areas prone to river flooding, resulting in a plethora of available products. Here we assess the potential and limitations of two main paradigms and provide guidance on the use of these global products in assessing flood risk in data-poor regions.
10.	Di Baldassarre, Giuliano, et al. (författare) Multiple hazards and risk perceptions over time : the availability heuristic in Italy and Sweden under COVID-19 2021 Ingår i: Natural hazards and earth system sciences. - : Copernicus Publications. - 1561-8633 .- 1684-9981. ; 21:11, s. 3439-3447 Tidskriftsartikel (refereegranskat)abstract The severe impact of global crises, such as COVID-19 and climate change, is plausibly reshaping the way in which people perceive risks. In this paper, we examine and compare how global crises and local disasters influence public perceptions of multiple hazards in Italy and Sweden. To this end, we integrate information about the occurrence of hazardous events with the results of two nationwide surveys. These included more than 4000 participants and were conducted in two different phases of the COVID-19 pandemic corresponding to low (August 2020) and high (November 2020) levels of infection rates. We found that, in both countries, people are more worried about risks related to experienced events. This is in line with the cognitive process known as the availability heuristic: individuals assess the risk associated with a given hazard based on how easily it comes to their mind. Epidemics, for example, are perceived as less likely and more impactful in Italy compared to Sweden. This outcome can be explained by cross-country differences in the impact of, as well as governmental responses to, COVID-19. Notwithstanding the ongoing pandemic, people in both Italy and Sweden are highly concerned about climate change, and they rank it as the most likely threat.
11.	Drobyshev, Igor (författare) Attribution of the role of climate change in the forest fires in Sweden 2018 2021 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 21, s. 2169-2179 Tidskriftsartikel (refereegranskat)abstract In this study, we analyse the role of climate change in the forest fires that raged through large parts of Sweden in the summer of 2018 from a meteorological perspective. This is done by studying the Canadian Fire Weather Index (FWI) based on sub-daily data, both in reanalysis data sets (ERA-Interim, ERA5, the Japanese 55 year Reanalysis, JRA-55, and Modern-Era Retrospective analysis for Research and Applications version 2, MERRA-2) and three large-ensemble climate models (EC-Earth, weather@home, W@H, and Community Earth System Model, CESM) simulations. The FWI, based on reanalysis, correlates well with the observed burnt area in summer (r = 0.6 to 0.8). We find that the maximum FWI in July 2018 had return times of similar to 24 years (90% CI, confidence interval, > 10 years) for southern and northern Sweden. Furthermore, we find a negative trend of the FWI for southern Sweden over the 1979 to 2017 time period in the reanalyses, yielding a non-significant reduced probability of such an event. However, the short observational record, large uncertainty between the reanalysis products and large natural variability of the FWI give a large confidence interval around this number that easily includes no change, so we cannot draw robust conclusions from reanalysis data.The three large-ensembles with climate models point to a roughly 1.1 (0.9 to 1.4) times increased probability (non-significant) for such events in the current climate relative to preindustrial climate. For a future climate (2 degrees C warming), we find a roughly 2 (1.5 to 3) times increased probability for such events relative to the preindustrial climate. The increased fire weather risk is mainly attributed to the increase in temperature. The other main factor, i.e. precipitation during summer months, is projected to increase for northern Sweden and decrease for southern Sweden. We, however, do not find a clear change in prolonged dry periods in summer months that could explain the increased fire weather risk in the climate models.In summary, we find a (non-significant) reduced probability of such events based on reanalyses, a small (nonsignificant) increased probability due to global warming up to now and a more robust (significant) increase in the risk for such events in the future based on the climate models.
12.	Ebert, Karin, et al. (författare) GIS analysis of effects of future Baltic sea level rise on the island of Gotland, Sweden 2016 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 16:7, s. 1571-1582 Tidskriftsartikel (refereegranskat)abstract Future sea level rise as a consequence of global warming will affect the world's coastal regions. Even though the pace of sea level rise is not clear, the consequences will be severe and global. Commonly the effects of future sea level rise are investigated for relatively vulnerable development countries; however, a whole range of varying regions needs to be considered in order to improve the understanding of global consequences. In this paper we investigate consequences of future sea level rise along the coast of the Baltic Sea island of Gotland, Sweden, with the aim to fill knowledge gaps regarding comparatively well-suited areas in developed countries. We study both the quantity of the loss of features of infrastructure, cultural, and natural value in the case of a 2 m sea level rise of the Baltic Sea and the effects of climate change on seawater intrusion in coastal aquifers, which indirectly cause saltwater intrusion in wells. We conduct a multi-criteria risk analysis by using lidar data on land elevation and GIS-vulnerability mapping, which gives the application of distance and elevation parameters formerly unimaginable precision. We find that in case of a 2 m sea level rise, 3 % of the land area of Gotland, corresponding to 99 km(2), will be inundated. The features most strongly affected are items of touristic or nature value, including camping places, shore meadows, sea stack areas, and endangered plants and species habitats. In total, 231 out of 7354 wells will be directly inundated, and the number of wells in the high-risk zone for saltwater intrusion in wells will increase considerably. Some valuable features will be irreversibly lost due to, for example, inundation of sea stacks and the passing of tipping points for seawater intrusion into coastal aquifers; others might simply be moved further inland, but this requires considerable economic means and prioritization. With nature tourism being one of the main income sources of Gotland, monitoring and planning are required to meet the changes. Seeing Gotland in a global perspective, this island shows that holistic multi-feature studies of future consequences of sea level rise are required to identify overall consequences for individual regions.
13.	Gabrovšek, Franci, et al. (författare) Karst show caves – how DTN technology as used in space assists automatic environmental monitoring and tourist protection – experiment in Postojna Cave 2014 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 14:2, s. 443-457 Tidskriftsartikel (refereegranskat)abstract The paper presents an experiment demonstrating a novel and successful application of delay- and disruption-tolerant networking (DTN) technology for automatic data transfer in a karst cave early warning and measuring system. The experiment took place inside the Postojna Cave in Slovenia, which is open to tourists. Several automatic meteorological measuring stations are set up inside the cave, as an adjunct to the surveillance infrastructure; the regular data transfer provided by the DTN technology allows the surveillance system to take on the role of an early warning system (EWS). One of the stations is set up alongside the railway tracks, which allows the tourist to travel inside the cave by train. The experiment was carried out by placing a DTN "data mule" (a DTN-enabled computer with WiFi connection) on the train and by upgrading the meteorological station with a DTN-enabled WiFi transmission system. When the data mule is in the wireless drive-by mode, it collects measurement data from the station over a period of several seconds as the train without stopping passes the stationary equipment, and delivers data at the final train station by the cave entrance. This paper describes an overview of the experimental equipment and organization allowing the use of a DTN system for data collection and an EWS inside karst caves where there is regular traffic of tourists and researchers.
14.	Joshi, Niranjan, et al. (författare) Probabilistic Seismic Hazard Assessment of Sweden Ingår i: Natural hazards and earth system sciences. - 1561-8633 .- 1684-9981. Tidskriftsartikel (refereegranskat)abstract Assessing seismic hazard in stable continental regions (SCR) such as Sweden poses unique challenges compared to active seismic regions. With diffuse seismicity, low seismicity rate, few large magnitude earthquakes and little strong motion data, estimating recurrence parameters and determining appropriate attenuation relationships is challenging. This study presents a probabilistic seismic hazard assessment of Sweden based on a recent earthquake catalogue which includes a large number of events with magnitudes ranging from 5.9 to -1.4, enabling recurrence parameters to be calculated for more source areas than in previous studies, and with less uncertainty. Recent ground motion models developed specifically for stable continental regions, including Fennoscandia, are used in logic trees accounting for their uncertainty and the hazard is calculated using the OpenQuake engine.The results are presented in the form of mean peak ground acceleration (PGA) maps at 475 and 2500 year return periods and hazard curves for four seismically active areas in Sweden. We find the highest hazard in the northernmost part of the country, in the post-glacial fault province. This is in contrast to previous studies, which have not considered the high seismic activity on the post-glacial faults. We also find relatively high hazard along the northeast coast and in southwestern Sweden, whereas the southeast and the mountain region to the northwest have low hazard.For a 475 year return period we estimate the highest PGAs to be 0.04-0.05g, in the far north, and for a 2500 year return period it is 0.1-0.15g in the same area. Significant uncertainties remain to be addressed in regards to the SCR seismicity in Sweden, including the homogenization of small local magnitudes with large moment magnitudes, the occurrence of large events in areas with little prior seismicity and the uncertainties surrounding the potential for large earthquakes on the post-glacial faults in northern Fennoscandia.
15.	Lindersson, Sara, et al. (författare) Global riverine flood risk - how do hydrogeomorphic floodplain maps compare to flood hazard maps? 2021 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 21:10, s. 2921-2948 Tidskriftsartikel (refereegranskat)abstract Riverine flood risk studies often require the identification of areas prone to potential flooding. This modelling process can be based on either (hydrologically derived) flood hazard maps or (topography-based) hydrogeomorphic floodplain maps. In this paper, we derive and compare riverine flood exposure from three global products: a hydrogeomorphic floodplain map (GFPLAIN250m, hereinafter GFPLAIN) and two flood hazard maps (Flood Hazard Map of the World by the European Commission's Joint Research Centre, hereinafter JRC, and the flood hazard maps produced for the Global Assessment Report on Disaster Risk Reduction 2015, hereinafter GAR). We find an average spatial agreement between these maps of around 30 % at the river basin level on a global scale. This agreement is highly variable across model combinations and geographic conditions, influenced by climatic humidity, river volume, topography, and coastal proximity. Contrary to expectations, the agreement between the two flood hazard maps is lower compared to their agreement with the hydrogeomorphic floodplain map. We also map riverine flood exposure for 26 countries across the global south by intersecting these maps with three human population maps (Global Human Settlement population grid, hereinafter GHS; High Resolution Settlement Layer, hereinafter HRSL; and WorldPop). The findings of this study indicate that hydrogeomorphic floodplain maps can be a valuable way of producing high-resolution maps of flood-prone zones to support riverine flood risk studies, but caution should be taken in regions that are dry, steep, very flat, or near the coast.
16.	Melchiorre, Caterina, et al. (författare) Application of a fast and efficient algorithm to assess landslide-prone areas in sensitive clays in Sweden 2015 Ingår i: Natural hazards and earth system sciences. - : European Geosciences Union (EGU). - 1561-8633 .- 1684-9981. ; 15:12, s. 2703-2713 Tidskriftsartikel (refereegranskat)abstract We refine and test an algorithm for landslide susceptibility assessment in areas with sensitive clays. The algorithm uses soil data and digital elevation models to identify areas which may be prone to landslides and has been applied in Sweden for several years. The algorithm is very computationally efficient and includes an intelligent filtering procedure for identifying and removing small-scale artifacts in the hazard maps produced. Where information on bedrock depth is available, this can be included in the analysis, as can information on several soil-type-based cross-sectional angle thresholds for slip. We evaluate how processing choices such as of filtering parameters, local cross-sectional angle thresholds, and inclusion of bedrock depth information affect model performance. The specific cross-sectional angle thresholds used were derived by analyzing the relationship between landslide scarps and the quick-clay susceptibility index (QCSI). We tested the algorithm in the Göta River valley. Several different verification measures were used to compare results with observed landslides and thereby identify the optimal algorithm parameters. Our results show that even though a relationship between the cross-sectional angle threshold and the QCSI could be established, no significant improvement of the overall modeling performance could be achieved by using these geographically specific, soil-based thresholds. Our results indicate that lowering the cross-sectional angle threshold from 1 : 10 (the general value used in Sweden) to 1 : 13 improves results slightly. We also show that an application of the automatic filtering procedure that removes areas initially classified as prone to landslides not only removes artifacts and makes the maps visually more appealing, but it also improves the model performance.
17.	Mondino, Elena, et al. (författare) Longitudinal survey data for diversifying temporal dynamics in flood risk modelling 2021 Ingår i: Natural hazards and earth system sciences. - : Copernicus Publications. - 1561-8633 .- 1684-9981. ; 21:9, s. 2811-2828 Tidskriftsartikel (refereegranskat)abstract Scholars have unravelled the complexities and underlying uncertainties in coupled human and water systems in various fields and disciplines. These complexities, however, are not always reflected in the way in which the dynamics of human–water systems are modelled. One reason is the lack of social data time series, which may be provided by longitudinal surveys. Here, we show the value of collecting longitudinal survey data to enrich sociohydrological modelling of flood risk. To illustrate, we compare and contrast two different approaches (repeated cross-sectional and panel) for collecting longitudinal data and explore changes in flood risk awareness and preparedness in a municipality hit by a flash flood in 2018. We found that risk awareness has not changed significantly in the timeframe under study (1 year). Perceived preparedness increased only among those respondents who suffered low damage during the flood event. We also found gender differences across both approaches for most of the variables explored. Lastly, we argue that results that are consistent across the two approaches can be used for the parametrisation of sociohydrological models. We posit that there is a need to enhance the representation of socio-demographic heterogeneity in modelling human–water systems in order to better support risk management.
18.	Montesarchio, Valeria, et al. (författare) Rainfall threshold definition using an entropy decision approach and radar data 2012 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 7, s. 2061-2074 Tidskriftsartikel (refereegranskat)abstract Flash flood events are floods characterised by a very rapid response of basins to storms, often resulting in loss of life and property damage. Due to the specific space-time scale of this type of flood, the lead time available for triggering civil protection measures is typically short. Rainfall threshold values specify the amount of precipitation for a given duration that generates a critical discharge in a given river cross section. If the threshold values are exceeded, it can produce a critical situation in river sites exposed to alluvial risk. It is therefore possible to directly compare the observed or forecasted precipitation with critical reference values, without running online real-time forecasting systems. The focus of this study is the Mignone River basin, located in Central Italy. The critical rainfall threshold values are evaluated by minimising a utility function based on the informative entropy concept and by using a simulation approach based on radar data. The study concludes with a system performance analysis, in terms of correctly issued warnings, false alarms and missed alarms.
19.	Nam, C. C., et al. (författare) Dependency of tropical cyclone risk on track in South Korea 2018 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 18:12, s. 3225-3234 Tidskriftsartikel (refereegranskat)abstract Several previous studies on tropical cyclone (TC) risk assessment have attempted to quantify the relationship between TC damage and its elements (i.e. exposure, vulnerability, and hazard). For hazard parameters, TC intensity (e.g. central minimum pressure, maximum wind speed) and size information (e.g. 30 knot radius of the TC) have been widely utilized. Our risk analysis of 85 TCs that made landfall in South Korea from 1979 to 2010, however, suggests that a small deviation of the TC track in the west-east direction (<= 250 km, smaller than the average radius of TC) has a more dominant effect on the extent and distribution of TC damage than TC intensity or size. This significant track dependency of TC damage exists because the TC track is responsible for the realization of hazard change from potential to active. More specifically, although two TCs may have the same intensity and size, locally experienced rainfall and wind speed can vary according to their tracks due to topography. These results suggest that track information should be considered more carefully in assessments of future TC risk.
20.	Pelascini, Lucas, et al. (författare) Finite-hillslope analysis of landslides triggered by excess pore water pressure: the roles of atmospheric pressure and rainfall infiltration during typhoons 2022 Ingår i: Natural Hazards and Earth System Science. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 22:10, s. 3125-3141 Tidskriftsartikel (refereegranskat)abstract Landslides are often triggered by catastrophic events, among which earthquakes and rainfall are the most depicted. However, very few studies have focused on the effect of atmospheric pressure on slope stability, even though weather events such as typhoons are associated with significant atmospheric pressure changes. Indeed, both atmospheric pressure changes and rainfall-induced groundwater level changes can generate large pore pressure changes. In this paper, we assess the respective impacts of atmospheric effects and rainfall over the stability of a hillslope. An analytical model of transient groundwater dynamics is developed to compute slope stability for finite hillslopes. Slope stability is evaluated through a safety factor based on the Mohr-Coulomb failure criterion. Both rainfall infiltration and atmospheric pressure variations, which impact slope stability by modifying the pore pressure of the media, are described by diffusion equations. The models were then forced by weather data from different typhoons that were recorded over Taiwan. While rainfall infiltration can induce pore pressure change up to hundreds of kilopascal, its effects are delayed in time due to flow and diffusion. To the contrary, atmospheric pressure change induces pore pressure changes not exceeding a few kilopascal, which propagates instantaneously through the skeleton before diffusion leads to an effective decay of pore pressure. Moreover, the effect of rainfall infiltration on slope stability decreases towards the toe of the hillslope and is cancelled where the water table reaches the surface, leaving atmospheric pressure change as the main driver of slope instability. This study allows for a better insight of slope stability through pore pressure analysis, and shows that atmospheric effects should not always be neglected.
21.	Pelascini, Lucas, et al. (författare) Modelling the control of groundwater on landslides triggering: the respective role of atmosphere and rainfall during typhoons 2022 Ingår i: Natural Hazards and Earth System Science. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. Tidskriftsartikel (refereegranskat)abstract Landslides are often triggered by catastrophic events, among which earthquakes and rainfall are the most depicted. However, very few studies have focused on the effect of atmospheric pressure on slope stability, even though weather events such as typhoons are associated with significant atmospheric pressure changes. Indeed, both atmospheric pressure changes and rainfallinduced groundwater level change can generate pore pressure changes with similar amplitude. In this paper, we assess the respective impacts of atmospheric effects and rainfall over the stability of a hillslope. An analytical model of transient groundwater dynamics is developed to compute slope stability for finite hillslopes. Slope stability is evaluated through a safety factor based on the Mohr-Coulomb failure criterion. Both rainfall infiltration and atmospheric pressure variations, which impact slope stability by modifying the pore pressure of the media, are described by diffusion equations. The models have then been forced by weather data from different typhoons that were recorded over Taiwan. While rainfall infiltration can induce pore pressure change up to hundred kPa, its effects is delayed in time due to diffusion. To the contrary, atmospheric pressure change induces pore pressure changes not exceeding a few kPa, but its effect is instantaneous. Moreover, the effect of rainfall infiltration on slope stability decreases towards the toe of the hillslope and is cancelled where the water table reaches the surface, leaving atmospheric pressure change as the main driver of slope instability. This study allows for a better insight of slope stability through pore pressure analysis, and shows that atmospheric effects shouldn’t always be neglected.
22.	Qin, Xinsheng, et al. (författare) A comparison of a two-dimensional depth-averaged flow model and a three-dimensional RANS model for predicting tsunami inundation and fluid forces 2018 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 18:9, s. 2489-2506 Tidskriftsartikel (refereegranskat)abstract The numerical modeling of tsunami inundation that incorporates the built environment of coastal communities is challenging for both 2-D and 3-D depth-integrated models, not only in modeling the flow but also in predicting forces on coastal structures. For depth-integrated 2-D models, inundation and flooding in this region can be very complex with variation in the vertical direction caused by wave breaking on shore and interactions with the built environment, and the model may not be able to produce enough detail. For 3-D models, a very fine mesh is required to properly capture the physics, dramatically increasing the computational cost and rendering impractical the modeling of some problems. In this paper, comparisons are made between Geo-Claw, a depth-integrated 2-D model based on the nonlinear shallow-water equations (NSWEs), and OpenFOAM, a 3-D model based on Reynolds-averaged Navier-Stokes (RANS) equation for tsunami inundation modeling. The two models were first validated against existing experimental data of a bore impinging onto a single square column. Then they were used to simulate tsunami inundation of a physical model of Seaside, Oregon. The resulting flow parameters from the models are compared and discussed, and these results are used to extrapolate tsunami-induced force predictions. It was found that the 2-D model did not accurately capture the important details of the flow near initial impact due to the transiency and large vertical variation of the flow. Tuning the drag coefficient of the 2-D model worked well to predict tsunami forces on structures in simple cases, but this approach was not always reliable in complicated cases. The 3-D model was able to capture transient characteristic of the flow, but at a much higher computational cost; it was found this cost can be alleviated by subdividing the region into reasonably sized subdomains without loss of accuracy in critical regions.
23.	Ridolfi, Elena, et al. (författare) An entropy approach for evaluating the maximum information content achievable by an urban rainfall network 2011 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 11:7, s. 2075-2083 Tidskriftsartikel (refereegranskat)abstract Hydrological models are the basis of operational flood-forecasting systems. The accuracy of these models is strongly dependent on the quality and quantity of the input information represented by rainfall height. Finer space-time rainfall resolution results in more accurate hazard forecasting. In this framework, an optimum raingauge network is essential in predicting flood events.This paper develops an entropy-based approach to evaluate the maximum information content achievable by a rainfall network for different sampling time intervals. The procedure is based on the determination of the coefficients of transferred and nontransferred information and on the relative isoinformation contours.The nontransferred information value achieved by the whole network is strictly dependent on the sampling time intervals considered. An empirical curve is defined, to assess the objective of the research: the nontransferred information value is plotted versus the associated sampling time on a semi-log scale. The curve has a linear trend.In this paper, the methodology is applied to the high-density raingauge network of the urban area of Rome.
24.	Seibert, Jan (författare) Comprehensive space-time hydrometeorological simulations for estimating very rare floods at multiple sites in a large river basin 2022 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 22, s. 2891-2920 Tidskriftsartikel (refereegranskat)abstract Estimates for rare to very rare floods are limited by the relatively short streamflow records available. Often, pragmatic conversion factors are used to quantify such events based on extrapolated observations, or simplifying assumptions are made about extreme precipitation and resulting flood peaks. Continuous simulation (CS) is an alternative approach that better links flood estimation with physical processes and avoids assumptions about antecedent conditions. However, long-term CS has hardly been implemented to estimate rare floods (i.e. return periods considerably larger than 100 years) at multiple sites in a large river basin to date. Here we explore the feasibility and reliability of the CS approach for 19 sites in the Aare River basin in Switzerland (area: 17 700 km2) with exceedingly long simulations in a hydrometeorological model chain. The chain starts with a multi-site stochastic weather generator used to generate 30 realizations of hourly precipitation and temperature scenarios of 10 000 years each. These realizations were then run through a bucket-type hydrological model for 80 sub-catchments and finally routed downstream with a simplified representation of main river channels, major lakes and relevant floodplains in a hydrologic routing system. Comprehensive evaluation over different temporal and spatial scales showed that the main features of the meteorological and hydrological observations are well represented and that meaningful information on low-probability floods can be inferred. Although uncertainties are still considerable, the explicit consideration of important processes of flood generation and routing (snow accumulation, snowmelt, soil moisture storage, bank overflow, lake and floodplain retention) is a substantial advantage. The approach allows for comprehensively exploring possible but unobserved spatial and temporal patterns of hydrometeorological behaviour. This is of particular value in a large river basin where the complex interaction of flows from individual tributaries and lake regulations are typically not well represented in the streamflow observations. The framework is also suitable for estimating more frequent floods, as often required in engineering and hazard mapping.
25.	Seibert, Jan (författare) Downsizing parameter ensembles for simulations of rare floods 2020 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 20, s. 3521-3549 Tidskriftsartikel (refereegranskat)abstract For extreme-flood estimation, simulation-based approaches represent an interesting alternative to purely statistical approaches, particularly if hydrograph shapes are required. Such simulation-based methods are adapted within continuous simulation frameworks that rely on statistical analyses of continuous streamflow time series derived from a hydrological model fed with long precipitation time series. These frameworks are, however, affected by high computational demands, particularly if floods with return periods > 1000 years are of interest or if modelling uncertainty due to different sources (meteorological input or hydrological model) is to be quantified. Here, we propose three methods for reducing the computational requirements for the hydrological simulations for extreme-flood estimation so that long streamflow time series can be analysed at a reduced computational cost. These methods rely on simulation of annual maxima and on analysing their simulated range to downsize the hydrological parameter ensemble to a small number suitable for continuous simulation frameworks. The methods are tested in a Swiss catchment with 10 000 years of synthetic streamflow data simulated thanks to a weather generator. Our results demonstrate the reliability of the proposed downsizing methods for robust simulations of rare floods with uncertainty. The methods are readily transferable to other situations where ensemble simulations are needed.
26.	Smith, E. A., et al. (författare) Transitioning from CRD to CDRD in Bayesian retrieval of rainfall from satellite passive microwave measurements : Part 3 - Identification of optimal meteorological tags 2013 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 13:5, s. 1185-1208 Tidskriftsartikel (refereegranskat)abstract In the first two parts of this study we have presented a performance analysis of our new Cloud Dynamics and Radiation Database (CDRD) satellite precipitation retrieval algorithm on various convective and stratiform rainfall case studies verified with precision radar ground truth data, and an exposition of the algorithm's detailed design in conjunction with a proof-of-concept analysis vis-a-vis its theoretical underpinnings. In this third part of the study, we present the underlying analysis used to identify what we refer to as the optimal metrological and geophysical tags, which are the optimally effective atmospheric and geographic parameters that are used to refine the selection of candidate microphysical profiles used for the Bayesian retrieval. These tags enable extending beyond the conventional Cloud Radiation Database (CRD) algorithm by invoking meteorological-geophysical guidance, drawn from a simulated database, which affect and are in congruence with the observed precipitation states. This is guidance beyond the restrictive control provided by only simulated radiative transfer equation (RTE) model-derived database brightness temperature (TB) vector proximity information in seeking to relate physically consistent precipitation profile solutions to individual satellite-observed TB vectors. The first two parts of the study have rigorously demonstrated that the optimal tags effectively mitigate against solution ambiguity, where use of only a CRD framework (TB guidance only) leads to pervasive non-uniqueness problems in finding rainfall solutions. Alternatively, a CDRD framework (TB + tag guidance) mitigates against non-uniqueness problems through improved constraints. It remains to show how these optimal tags are identified. By use of three statistical analysis procedures applied to a database from 120 North American atmospheric simulations of precipitating storms (independent of the 60 simulations for the European-Mediterranean basin region used in the Parts 1 and 2 studies), we examine 25 separate dynamical-thermodynamical-hydrological (DST) and geophysical parameters for their relationships to rainfall variables - specifically, surface rain rate and columnar liquid/ice/total water paths of precipitating hydrometeors. The analysis identifies seven optimal parameter tags which exceed all others in the strengths of their correlations to the precipitation variables but also have observational counterparts in the operational global forecast model outputs. The seven optimal tags are (1 and 2) vertical velocities at 700 and 500 hPa; (3) equivalent potential temperature at surface; (4) convective available potential energy; (5) moisture flux 50 hPa above surface; (6) freezing level height; and (7) terrain height, i.e., surface height.
27.	Turkington, Thea, et al. (författare) Empirical atmospheric thresholds for debris flows and flash floodsin the southern French Alps 2014 Ingår i: Natural hazards and earth system sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 14, s. 1517-1530 Tidskriftsartikel (refereegranskat)abstract Debris flows and flash floods are often preceded by intense, convective rainfall. The establishment of reliable rainfall thresholds is an important component for quantitative hazard and risk assessment, and for the development of an early warning system. Traditional empirical thresholds based on peak intensity, duration and antecedent rainfall can be difficult to verify due to the localized character of the rainfall and the absence of weather radar or sufficiently dense rain gauge networks in mountainous regions. However, convective rainfall can be strongly linked to regional atmospheric patterns and profiles. There is potential to employ this in empirical threshold analysis. This work develops a methodology to determine robust thresholds for flash floods and debris flows utilizing regional atmospheric conditions derived from ECMWF ERA-Interim reanalysis data, comparing the results with rain-gauge-derived thresholds. The method includes selecting the appropriate atmospheric indicators, categorizing the potential thresholds, determining and testing the thresholds. The method is tested in the Ubaye Valley in the southern French Alps (548 km2), which is known to have localized convection triggered debris flows and flash floods. This paper shows that instability of the atmosphere and specific humidity at 700 hPa are the most important atmospheric indicators for debris flows and flash floods in the study area. Furthermore, this paper demonstrates that atmospheric reanalysis data are an important asset, and could replace rainfall measurements in empirical exceedance thresholds for debris flows and flash floods.
28.	Vicente-Serrano, S. M., et al. (författare) A high-resolution spatial assessment of the impacts of drought variability on vegetation activity in Spain from 1981 to 2015 2019 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1561-8633 .- 1684-9981. ; 19:6, s. 1189-1213 Tidskriftsartikel (refereegranskat)abstract Drought is a major driver of vegetation activity in Spain, with significant impacts on crop yield, forest growth, and the occurrence of forest fires. Nonetheless, the sensitivity of vegetation to drought conditions differs largely amongst vegetation types and climates. We used a high-resolution (1.1 km) spatial dataset of the normalized difference vegetation index (NDVI) for the whole of Spain spanning the period from 1981 to 2015, combined with a dataset of the standardized precipitation evapotranspiration index (SPEI) to assess the sensitivity of vegetation types to drought across Spain. Specifically, this study explores the drought timescales at which vegetation activity shows its highest response to drought severity at different moments of the year. Results demonstrate that - over large areas of Spain - vegetation activity is controlled largely by the interannual variability of drought. More than 90% of the land areas exhibited statistically significant positive correlations between the NDVI and the SPEI during dry summers (JJA). Nevertheless, there are some considerable spatio-temporal variations, which can be linked to differences in land cover and aridity conditions. In comparison to other climatic regions across Spain, results indicate that vegetation types located in arid-regions showed the strongest response to drought. Importantly, this study stresses that the timescale at which drought is assessed is a dominant factor in understanding the different responses of vegetation activity to drought. RAMS MD, 1990, FOREST SCIENCE, V36, P970
29.	Weyrich, Philippe, et al. (författare) A flood-risk-oriented, dynamic protection motivation framework to explain risk reduction behaviours 2020 Ingår i: Natural hazards and earth system sciences. - : Copernicus Gesellschaft mbH. - 1561-8633 .- 1684-9981. ; 20:1, s. 287-298 Tidskriftsartikel (refereegranskat)abstract Private risk reduction behaviours can significantly reduce the negative impacts of flooding and flash floods. Over the past decades, researchers have used various socio-cognitive models or threat and coping mechanisms to explain individual protective behaviours. However, these models ignore the fact that people are not equally ready to act upon a danger, and they (the models) give limited insights into the effectiveness of communication strategies to foster risk reduction behaviours. Therefore, we explored the current state of homeowners' readiness to undertake risk reduction behaviours in flood risk areas by applying a dynamic protection motivation framework. We conducted a survey in an Italian municipality that experienced severe flash flooding in September 2018. The results show that people are motivated by different factors in prompting risk reduction behaviour based on their chosen types of protective measures. For example, people that undertook structural or avoidance measures are more likely to be motivated to protect themselves by increased perceptions of vulnerability and response efficacy and are less worried about expected flood losses compared to people that undertook only basic emergency measures. In this paper, we argue how these new insights contribute to targeting flood risk communication strategies to groups of individuals characterized by different readiness stages and motivations to protect themselves.
30.	Bengtsson, Anders, et al. (författare) Extreme value modelling of storm damage in Swedish forests 2007 Ingår i: Natural Hazards and Earth System Sciences. - 1684-9981. ; 7:5, s. 515-521 Tidskriftsartikel (refereegranskat)abstract Forests cover about 56% of the land area in Sweden and forest damage due to strong winds has been a recurring problem. In this paper we analyse recorded storm damage in Swedish forests for the years 1965-2007. During the period 48 individual storm events with a total damage of 164 Mm(3) have been reported with the severe storm on 8 to 9 January 2005, as the worst with 70 Mm(3) damaged forest. For the analysis, storm damage data has been normalised to account for the increase in total forest volume over the period. We show that, within the framework of statistical extreme value theory, a Poisson point process model can be used to describe these storm damage events. Damage data supports a heavy-tailed distribution with great variability in damage for the worst storm events. According to the model, and in view of available data, the return period for a storm with damage in size of the severe storm of January 2005 is approximately 80 years, i.e. a storm with damage of this magnitude will happen, on average, once every eighty years. To investigate a possible temporal trend, models with time-dependent parameters have been analysed but give no conclusive evidence of an increasing trend in the normalised storm damage data for the period. Using a non-parametric approach with a kernel based local-likelihood method gives the same result.
31.	Iannacone, Leandro, et al. (författare) Simulating multi-hazard event sets for life cycle consequence analysis 2024 Ingår i: Natural Hazards and Earth System Sciences. - 1561-8633. ; 24:5, s. 1721-1740 Tidskriftsartikel (refereegranskat)abstract In the context of natural hazard risk quantification and modeling of hazard interactions, some literature separates “Level I” (or occurrence) interactions from “Level II” (or consequence) interactions. The Level I interactions occur inherently due to the nature of the hazards, independently of the presence of physical assets. In such cases, one hazard event triggers or modifies the occurrence of another (e.g., flooding due to heavy rain, liquefaction and landslides triggered by an earthquake), thus creating a dependency between the features characterizing such hazard events. They differ from Level II interactions, which instead occur through impacts/consequences on physical assets/components and systems (e.g., accumulation of physical damage or social impacts due to earthquake sequences, landslides due to the earthquake-induced collapse of a retaining structure). Multi-hazard life cycle consequence (LCCon) analysis aims to quantify the consequences (e.g., repair costs, downtime, casualty rates) throughout a system’s service life and should account for both Level I and II interactions. The available literature generally considers Level I interactions – the focus of this study – mainly defining relevant taxonomies, often qualitatively, without providing a computational framework to simulate a sequence of hazard events incorporating the identified interrelations among them. This paper addresses this gap, proposing modeling approaches associated with different types of Level I interactions. It describes a simulation-based method for generating multi-hazard event sets (i.e., a sequence of hazard events and associated features throughout the system’s life cycle) based on the theory of competing Poisson processes. The proposed approach incorporates the different types of interactions in a sequential Monte Carlo sampling method. The method outputs multi-hazard event sets that can be integrated into LCCon frameworks to quantify interacting hazard consequences. An application incorporating several hazard interactions is presented to illustrate the potential of the proposed method.
32.	Jönsson, Anna Maria, et al. (författare) Ensemble analysis of frost damage on vegetation caused by spring backlashes in a warmer Europe 2011 Ingår i: Natural Hazards and Earth System Sciences. - : Copernicus GmbH. - 1684-9981. ; 11:2, s. 401-418 Tidskriftsartikel (refereegranskat)abstract Tree dehardening and budburst will occur earlier in a warmer climate, and this could lead to an increased risk of frost damage caused by temperature backlashes. By using a spring backlash index and a cold hardiness model, we assessed different aspects of risk for frost damage in Norway spruce forests during the present climate and for one future emission scenario. Uncertainties associated with climate modelling were quantified by using temperature data from three climate data sets: (1) E-Obs gridded observed climate data, (2) an ensemble of data from eight regional climate models (RCM) forced by ERA-40 reanalysis data, (3) an ensemble of regional climate scenarios produced by the regional climate model RCA3 driven at the boundary conditions by seven global climate models (GCM), all representing the SRES A1B emission scenario. The frost risk was analysed for three periods, 1961-1990, 2011-2040 and 2070-2097. The RCA3 GCM ensemble indicated that the risk for spring frost damage may increase in the boreo-nemoral forest zone of southern Scandinavia and the Baltic states/Belarus. This is due to an increased frequency of backlashes, lower freezing temperatures after the onset of the vegetation period and the last spring frost occurring when the trees are closer to budburst. The changes could be transient due to the fine balance between an increased risk of frost damage caused by dehardening during a period when freezing temperatures are common and a decreased risk caused by warmer temperatures. In the nemoral zone, the zone with highest risk for spring backlashes during the reference period (1961-1990), the spring frost severity may increase due to frost events occurring when the trees are closer to budburst. However, the risk in terms of frequency of backlashes and freezing temperature were projected to become lower already in the beginning of this century.

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