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  • 1.
    Berg, Peter
    et al.
    SMHI, Research Department, Hydrology.
    Christensen, Ole B.
    Klehmet, Katharina
    SMHI, Research Department, Hydrology.
    Lenderink, Geert
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Teichmann, Claas
    Yang, Wei
    SMHI, Research Department, Hydrology.
    Summertime precipitation extremes in a EURO-CORDEX 0.11 degrees ensemble at an hourly resolution2019In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 19, no 4, p. 957-971Article in journal (Refereed)
  • 2.
    Beven, Keith
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lancaster Environment Centre, Lancaster University, Lancaster, UK.
    Almeida, Susana
    Univ Bristol, Dept Civil Engn, Bristol, Avon, England.
    Aspinall, Willy P.
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Bates, Paul D.
    Univ Bristol, Sch Geog Sci, Bristol, Avon, England.
    Blazkova, Sarka
    TG Masaryk Water Resource Inst, Prague, Czech Republic.
    Borgomeo, Edoardo
    Univ Oxford, Environm Change Inst, Oxford, England.
    Freer, Jim
    Univ Bristol, Sch Geog Sci, Bristol, Avon, England.
    Goda, Katsuichiro
    Univ Bristol, Dept Civil Engn, Bristol, Avon, England.
    Hall, Jimw.
    Univ Oxford, Environm Change Inst, Oxford, England.
    Phillips, Jeremy C.
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Simpson, Michael
    Univ Oxford, Environm Change Inst, Oxford, England.
    Smith, Paul J.
    Univ Lancaster, Lancaster Environm Ctr, Lancaster, England;Waternumbers Ltd, Halton Mill, Lancaster LA2 6DN, England.
    Stephenson, David B.
    Univ Exeter, Dept Math & Comp Sci, Exeter, Devon, England.
    Wagener, Thorsten
    Univ Bristol, Dept Civil Engn, Bristol, Avon, England;Univ Bristol, Cabot Inst, Bristol, Avon, England.
    Watson, Matt
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Wilkins, Kate L.
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Epistemic uncertainties and natural hazard risk assessment - Part 1: A review of different natural hazard areas2018In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 18, no 10, p. 2741-2768Article, review/survey (Refereed)
    Abstract [en]

    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).

  • 3.
    Beven, Keith
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Univ Lancaster, Lancaster Environm Ctr, Lancaster, England.
    Aspinall, Willy P.
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Bates, Paul D.
    Univ Bristol, Sch Geog Sci, Bristol, Avon, England.
    Borgomeo, Edoardo
    Univ Oxford, Environm Change Inst, Oxford, England.
    Goda, Katsuichiro
    Univ Bristol, Dept Civil Engn, Bristol, Avon, England.
    Hall, Jim W.
    Univ Oxford, Environm Change Inst, Oxford, England.
    Page, Trevor
    Univ Lancaster, Lancaster Environm Ctr, Lancaster, England.
    Phillips, Jeremy C.
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Simpson, Michael
    Univ Oxford, Environm Change Inst, Oxford, England.
    Smith, Paul J.
    Univ Lancaster, Lancaster Environm Ctr, Lancaster, England;European Ctr Medium Range Weather Forecasting, Reading, Berks, England.
    Wagener, Thorsten
    Univ Bristol, Dept Civil Engn, Bristol, Avon, England;Univ Bristol, Cabot Inst, Bristol, Avon, England.
    Watson, Matt
    Univ Bristol, Sch Earth Sci, Bristol, Avon, England.
    Epistemic uncertainties and natural hazard risk assessment - Part 2: What should constitute good practice?2018In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 18, no 10, p. 2769-2783Article in journal (Refereed)
    Abstract [en]

    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.

  • 4. Buchecker, M.
    et al.
    Salvini, G.
    Di Baldassarre, Giuliano
    UNESCO-IHE Institute for Water Education, Delft, the Netherlands.
    Semenzin, E.
    Maidl, E.
    Marcomini, A.
    The role of risk perception in making flood risk management more effective2013In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 13, p. 3013-3030Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Darmawan, Herlan
    et al.
    GFZ German Res Ctr Geosci, Dept Phys Earth, D-14473 Potsdam, Germany;Univ Gadjah Mada, Fac Math & Nat Sci, Dept Phys, Lab Geophys, Yogyakarta 55281, Indonesia.
    Walter, Thomas R.
    GFZ German Res Ctr Geosci, Dept Phys Earth, D-14473 Potsdam, Germany.
    Troll, Valentin R.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. Univ Padjajaran, Fac Geol Engn, Bandung 45363, Indonesia.
    Budi-Santoso, Agus
    BPPTKG, Jalan Cendana 15, Yogyakarta 55166, Indonesia.
    Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption2018In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 18, no 12, p. 3267-3281Article in journal (Refereed)
    Abstract [en]

    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.

  • 6. Depietri, Yaella
    et al.
    Dahal, Khila
    McPhearson, Timon
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. The New School, USA; Cary Institute of Ecosystem Studies, USA.
    Multi-hazard risks in New York City2018In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 18, no 12, p. 3363-3381Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Drozdzewski, Danielle
    et al.
    University of New South Wales.
    Shaw, W
    Dominey-Howes, Dale
    Brander, R
    Walton, T
    Gero, A
    Sherker, S
    Goff, J
    Edwick, B
    Surveying rip current survivors: preliminary insights into the experiences of being caught in rip currents2012In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 12, no 4, p. 1201-1211Article in journal (Refereed)
  • 8.
    Ebert, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ekstedt, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    GIS analysis of effects of future Baltic sea level rise on the island of Gotland, Sweden2016In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 16, no 7, p. 1571-1582Article in journal (Refereed)
    Abstract [en]

    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.

  • 9.
    Gabrovšek, Franci
    et al.
    Karst Research Institute, Research Centre of the Slovenian Academy of Sciences and Arts.
    Grašič, Bostjan
    MEIS d.o.o., Mali Vrh pri Šmarju, Slovenia.
    Božnar, Marija Zlata
    MEIS d.o.o., Mali Vrh pri Šmarju, Slovenia.
    Udén, Maria
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Human Work Science.
    Elwyn, Davies
    Folly Consulting Ltd.
    Karst show caves: How DTN technology as used in space assists automatic environmental monitoring and tourist protection - experiment in Postojna cave2014In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 14, no 2, p. 443-457Article in journal (Refereed)
    Abstract [en]

    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.

  • 10. Jonsson, A. M.
    et al.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Ensemble analysis of frost damage on vegetation caused by spring backlashes in a warmer Europe2011In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 11, no 2, p. 401-418Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Kållberg, Per
    et al.
    SMHI, Research Department, Meteorology.
    Montani, A.
    A case study carried out with two different NWP systems2006In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 6, no 5, p. 755-760Article in journal (Refereed)
    Abstract [en]

    A model intercomparison between two atmospheric models, the non-hydrostatic Lokal Modell (LM) and the hydrostatic HIgh Resolution Limited Area Model (HIRLAM) is carried out for a one-week period, including a case of cyclogeneis leading to heavy precipitation over Northern Italy. The two models, very different in terms of data-assimilation and numerics, provide different results in terms of forecasts of surface fields. Opposite diurnal biases for the two models are found in terms of screen level temperatures. HIRLAM wind speed forecasts are too strong, while LM precipitation forecasts have larger extremes. The intercomparison exercise identifies some systematic differences in the weather products generated by the two systems and sheds some light on the biases of the two numerical weather prediction systems.

  • 12.
    Melchiorre, Caterina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Tryggvason, Ari
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Application of a fast and efficient algorithm to assess landslide-prone areas in sensitive clays in Sweden2015In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 15, no 12, p. 2703-2713Article in journal (Refereed)
    Abstract [en]

    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.

  • 13.
    Montesarchio, Valeria
    et al.
    Sapienza University of Rome, Rome, Italy.
    Ridolfi, Elena
    Sapienza University of Rome, Rome, Italy.
    Russo, Fabio
    Sapienza University of Rome.
    Napolitano, Francesco
    Sapienza University of Rome.
    Rainfall threshold definition using an entropy decision approach and radar data2012In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 7, p. 2061-2074Article in journal (Refereed)
    Abstract [en]

    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.

  • 14.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Spatio-temporal precipitation error propagation in runoff modelling: a case study in central Sweden2006In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 6, no 4, p. 597-609Article in journal (Refereed)
    Abstract [en]

    The propagation of spatio-temporal errors in precipitation estimates to runoff errors in the output from the conceptual hydrological HBV model was investigated. The study region was the Giman catchment in central Sweden, and the period year 2002. Five precipitation sources were considered: NWP model (H22), weather radar (RAD), precipitation gauges (PTH), and two versions of a mesoscale analysis system (M11, M22). To define the baseline estimates of precipitation and runoff, used to define seasonal precipitation and runoff biases, the mesoscale climate analysis M11 was used. The main precipitation biases were a systematic overestimation of precipitation by H22, in particular during winter and early spring, and a pronounced local overestimation by RAD during autumn, in the western part of the catchment. These overestimations in some cases exceeded 50% in terms of seasonal subcatchment relative accumulated volume bias, but generally the bias was within +/- 20%. The precipitation data from the different sources were used to drive the HBV model, set up and calibrated for two stations in Giman, both for continuous simulation during 2002 and for forecasting of the spring flood peak. In summer, autumn and winter all sources agreed well. In spring H22 overestimated the accumulated runoff volume by similar to 50% and peak discharge by almost 100%, owing to both overestimated snow depth and precipitation during the spring flood. PTH overestimated spring runoff volumes by similar to 15% owing to overestimated winter precipitation. The results demonstrate how biases in precipitation estimates may exhibit a substantial space-time variability, and may further become either magnified or reduced when applied for hydrological purposes, depending on both temporal and spatial variations in the catchment. Thus, the uncertainty in precipitation estimates should preferably be specified as a function of both time and space.

  • 15.
    Qin, Xinsheng
    et al.
    Univ Washington, Dept Civil & Environm Engn, More Hall Box 352700, Seattle, WA 98195 USA..
    Motley, Michael
    Univ Washington, Dept Civil & Environm Engn, More Hall Box 352700, Seattle, WA 98195 USA..
    LeVeque, Randall
    Univ Washington, Dept Appl Math, Seattle, WA 98195 USA..
    Gonzalez, Frank
    Univ Washington, Dept Earth & Space Sci, Seattle, WA 98195 USA..
    Mueller, Kaspar
    KTH, School of Computer Science and Communication (CSC).
    A comparison of a two-dimensional depth-averaged flow model and a three-dimensional RANS model for predicting tsunami inundation and fluid forces2018In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 18, no 9, p. 2489-2506Article in journal (Refereed)
    Abstract [en]

    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.

  • 16.
    Ridolfi, Elena
    et al.
    Sapienza University of Rome, Rome, Italy.
    Montesarchio, Valeria
    Sapienza University of Rome, Rome, Italy.
    Russo, Fabio
    Sapienza University of Rome.
    Napolitano, Francesco
    Sapienza University of Rome.
    An entropy approach for evaluating the maximum information content achievable by an urban rainfall network2011In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 11, no 7, p. 2075-2083Article in journal (Refereed)
    Abstract [en]

    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.

  • 17. Smith, E. A.
    et al.
    Leung, Wing Y. H.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Sano, P.
    Transitioning from CRD to CDRD in Bayesian retrieval of rainfall from satellite passive microwave measurements: Part 3 - Identification of optimal meteorological tags2013In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 13, no 5, p. 1185-1208Article in journal (Refereed)
    Abstract [en]

    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.

  • 18. Turkington, Thea
    et al.
    Ettema, Janneke
    van Westen, Cees
    Breinl, Korbinian
    Empirical atmospheric thresholds for debris flows and flash floodsin the southern French Alps2014In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 14, p. 1517-1530Article in journal (Refereed)
    Abstract [en]

    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.

  • 19.
    Wetterhall, Fredrik
    et al.
    SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Andreasson, Johan
    SMHI, Professional Services.
    Rosberg, Jörgen
    SMHI, Research Department, Hydrology.
    Yang, Wei
    SMHI, Research Department, Hydrology.
    Using ensemble climate projections to assess probabilistic hydrological change in the Nordic region2011In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 11, no 8, p. 2295-2306Article in journal (Refereed)
    Abstract [en]

    Assessing hydrological effects of global climate change at local scales is important for evaluating future hazards to society. However, applying climate model projections to local impact models can be difficult as outcomes can vary considerably between different climate models, and including results from many models is demanding. This study combines multiple climate model outputs with hydrological impact modelling through the use of response surfaces. Response surfaces represent the sensitivity of the impact model to incremental changes in climate variables and show probabilies for reaching a priori determined thresholds. Response surfaces were calculated using the HBV hydrological model for three basins in Sweden. An ensemble of future climate projections was then superimposed onto each response surface, producing a probability estimate for exceeding the threshold being evaluated. Site specific impacts thresholds were used where applicable. Probabilistic trends for future change in hazards or potential can be shown and evaluated. It is particularly useful for visualising the range of probable outcomes from climate models and can easily be updated with new results as they are made available.

  • 20.
    Weyrich, Philippe
    et al.
    ETH Zürich.
    Mondino, Elena
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Borga, Marco
    University of Padova.
    Di Baldassarre, Giuliano
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Patt, Anthony
    ETH Zürich.
    Scolobig, Anna
    University of Geneva.
    A flood-risk-oriented, dynamic protection motivation framework to explain risk reduction behaviours2020In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 20, p. 287-298Article in journal (Refereed)
    Abstract [en]

    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.

  • 21.
    Yang, Wei
    et al.
    SMHI, Research Department, Hydrology.
    Gardelin, Marie
    SMHI, Professional Services.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Bosshard, Thomas
    SMHI, Research Department, Hydrology.
    Multi-variable bias correction: application of forest fire risk in present and future climate in Sweden2015In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 15, no 9, p. 2037-2057Article in journal (Refereed)
    Abstract [en]

    As the risk of a forest fire is largely influenced by weather, evaluating its tendency under a changing climate becomes important for management and decision making. Currently, biases in climate models make it difficult to realistically estimate the future climate and consequent impact on fire risk. A distribution-based scaling (DBS) approach was developed as a post-processing tool that intends to correct systematic biases in climate modelling outputs. In this study, we used two projections, one driven by historical reanalysis (ERA40) and one from a global climate model (ECHAM5) for future projection, both having been dynamically down-scaled by a regional climate model (RCA3). The effects of the post-processing tool on relative humidity and wind speed were studied in addition to the primary variables precipitation and temperature. Finally, the Canadian Fire Weather Index system was used to evaluate the influence of changing meteorological conditions on the moisture content in fuel layers and the fire-spread risk. The forest fire risk results using DBS are proven to better reflect risk using observations than that using raw climate outputs. For future periods, southern Sweden is likely to have a higher fire risk than today, whereas northern Sweden will have a lower risk of forest fire.

1 - 21 of 21
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