Pub Date : 2023-08-01DOI: 10.5194/nhess-23-2697-2023
Haixia Zhang, Cheng Meng, W. Fang
Abstract. The impact of natural hazards such as storm surges and waves on coastal areas during extreme tropical cyclone (TC) events can be amplified by the cascading effects of multiple hazards. Quantitative estimation of the marginal distribution and joint probability distribution of storm surges and waves is essential to understanding and managing tropical cyclone disaster risks. In this study, the dependence between storm surges and waves is quantitatively assessed using the extreme value theory (EVT) and the copula function for the Leizhou Peninsula and the island of Hainan of China, based on numerically simulated surge heights (SHs) and significant wave heights (SWHs) for every 30 min from 1949 to 2013. The steps for determining coastal protection standards in scalar values are also demonstrated. It is found that the generalized extreme value (GEV) function and Gumbel copula function are suitable for fitting the marginal and joint distribution characteristics of the SHs and SWHs, respectively, in this study area. Secondly, the SHs show higher values as locations get closer to the coastline, and the SWHs become higher further from the coastline. Lastly, the optimal design values of SHs and SWHs under different joint return periods can be estimated using the nonlinear programming method. This study shows the effectiveness of the bivariate copula function in evaluating the probability for different scenarios, providing a valuable reference for optimizing the design of engineering protection standards.
{"title":"Joint probability analysis of storm surges and waves caused by tropical cyclones for the estimation of protection standard: a case study on the eastern coast of the Leizhou Peninsula and the island of Hainan in China","authors":"Haixia Zhang, Cheng Meng, W. Fang","doi":"10.5194/nhess-23-2697-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2697-2023","url":null,"abstract":"Abstract. The impact of natural hazards such as storm surges and\u0000waves on coastal areas during extreme tropical cyclone (TC) events can be\u0000amplified by the cascading effects of multiple hazards. Quantitative\u0000estimation of the marginal distribution and joint probability distribution\u0000of storm surges and waves is essential to understanding and managing\u0000tropical cyclone disaster risks. In this study, the dependence between storm\u0000surges and waves is quantitatively assessed using the extreme value theory\u0000(EVT) and the copula function for the Leizhou Peninsula and the island of Hainan of\u0000China, based on numerically simulated surge heights (SHs) and\u0000significant wave heights (SWHs) for every 30 min from 1949 to 2013. The\u0000steps for determining coastal protection standards in scalar values are also\u0000demonstrated. It is found that the generalized extreme value (GEV) function\u0000and Gumbel copula function are suitable for fitting the marginal and joint\u0000distribution characteristics of the SHs and SWHs, respectively, in this\u0000study area. Secondly, the SHs show higher values as locations get closer to\u0000the coastline, and the SWHs become higher further from the coastline.\u0000Lastly, the optimal design values of SHs and SWHs under different joint\u0000return periods can be estimated using the nonlinear programming method.\u0000This study shows the effectiveness of the bivariate copula function in\u0000evaluating the probability for different scenarios, providing a valuable\u0000reference for optimizing the design of engineering protection standards.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42265111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-31DOI: 10.5194/nhess-23-2683-2023
Asim M. Khawaja, Behnam Maleki Asayesh, S. Hainzl, D. Schorlemmer
Abstract. Aftershock forecast models are usually provided on a uniform spatial grid, and the receiver operating characteristic (ROC) curve is often employed for evaluation, drawing a binary comparison of earthquake occurrences or non-occurrence for each grid cell. However, synthetic tests show flaws in using the ROC for aftershock forecast ranking. We suggest a twofold improvement in the testing strategy. First, we propose to replace ROC with the Matthews correlation coefficient (MCC) and the F1 curve. We also suggest using a multi-resolution test grid adapted to the earthquake density. We conduct a synthetic experiment where we analyse aftershock distributions stemming from a Coulomb failure (ΔCFS) model, including stress activation and shadow regions. Using these aftershock distributions, we test the true ΔCFS model as well as a simple distance-based forecast (R), only predicting activation. The standard test cannot clearly distinguish between both forecasts, particularly in the case of some outliers. However, using both MCC-F1 instead of ROC curves and a simple radial multi-resolution grid improves the test capabilities significantly. The novel findings of this study suggest that we should have at least 8 % and 5 % cells with observed earthquakes to differentiate between a near-perfect forecast model and an informationless forecast using ROC and MCC-F1, respectively. While we cannot change the observed data, we can adjust the spatial grid using a data-driven approach to reduce the disparity between the number of earthquakes and the total number of cells. Using the recently introduced Quadtree approach to generate multi-resolution grids, we test real aftershock forecast models for Chi-Chi and Landers aftershocks following the suggested guideline. Despite the improved tests, we find that the simple R model still outperforms the ΔCFS model in both cases, indicating that the latter should not be applied without further model adjustments.
{"title":"Towards improving the spatial testability of aftershock forecast models","authors":"Asim M. Khawaja, Behnam Maleki Asayesh, S. Hainzl, D. Schorlemmer","doi":"10.5194/nhess-23-2683-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2683-2023","url":null,"abstract":"Abstract. Aftershock forecast models are usually provided on a uniform spatial grid, and the receiver operating characteristic (ROC) curve is often employed for evaluation, drawing a binary comparison of earthquake occurrences or non-occurrence for each grid cell. However, synthetic tests show flaws in using the ROC for aftershock forecast ranking. We suggest a twofold improvement in the testing strategy. First, we propose to replace ROC with the Matthews correlation coefficient (MCC) and the F1 curve. We also suggest using a multi-resolution test grid adapted to the earthquake density. We conduct a synthetic experiment where we analyse aftershock distributions stemming from a Coulomb failure (ΔCFS) model, including stress activation and shadow regions. Using these aftershock distributions, we test the true ΔCFS model as well as a simple distance-based forecast (R), only predicting activation. The standard test cannot clearly distinguish between both forecasts, particularly in the case of some outliers. However, using both MCC-F1 instead of ROC curves and a simple radial multi-resolution grid improves the test capabilities significantly. The novel findings of this study suggest that we should have at least 8 % and 5 % cells with observed earthquakes to differentiate between a near-perfect forecast model and an informationless forecast using ROC and MCC-F1, respectively. While we cannot change the observed data, we can adjust the spatial grid using a data-driven approach to reduce the disparity between the number of earthquakes and the total number of cells. Using the recently introduced Quadtree approach to generate multi-resolution grids, we test real aftershock forecast models for Chi-Chi and Landers aftershocks following the suggested guideline. Despite the improved tests, we find that the simple R model still outperforms the ΔCFS model in both cases, indicating that the latter should not be applied without further model adjustments.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46683343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-28DOI: 10.5194/nhess-23-2663-2023
Betina I. Guido, I. Popescu, V. Samadi, B. Bhattacharya
Abstract. Floods are among the most destructive natural hazards in the world, posing numerous risks to societies and economies globally. Accurately understanding and modeling floods driven by extreme rainfall events has long been a challenging task in the domains of hydrologic science and engineering. Unusual catchment responses to flooding cause great difficulty in predicting the variability and magnitude of floods, as well as proposing solutions to manage large volumes of overland flow. The usage of nature-based solutions (NBSs) has proved to be effective in the mitigation of flood peak rate and volume in urban or coastal areas, yet it is still not widely implemented due to limited knowledge and testing compared to traditional engineering solutions. This research examined an integrated hydrological and hydraulic modeling system to understand the response of an at-risk watershed system to flooding and evaluate the efficacy of NBS measures. Using the Hydrologic Engineering Center Hydrologic Modeling System and River Analysis System (HEC-HMS and HEC-RAS) software, an integrated hydrologic–hydraulic model was developed for Hurricane Matthew- (2016) and Florence-driven (2018) floods across the Little Pee Dee–Lumber River watershed, North and South Carolina (the Carolinas), US. The focus was on Nichols, a small town that has disproportionately been impacted by flooding during these two hurricane events. The present article proposes a methodology for selecting, modeling, and evaluating the performance of NBS measures within a catchment, which can be extended to other case studies. Different NBS measures, including flood storage ponds, riparian reforestation, and afforestation in croplands, were designed, modeled, and evaluated. Hurricane Matthew's flooding event was used for evaluating the NBS scenarios given its high simulation accuracy in flood inundation compared to the less accurate results obtained for Hurricane Florence. The scenario comparison evidenced that large-scale natural interventions, such as afforestation in croplands, can reduce the inundated area in Nichols by 8 % to 18 %. On the contrary, the smaller-scale interventions such as riparian reforestation and flood storage ponds showed a negligible effect of only 1 % on flood mitigation.
{"title":"An integrated modeling approach to evaluate the impacts of nature-based solutions of flood mitigation across a small watershed in the southeast United States","authors":"Betina I. Guido, I. Popescu, V. Samadi, B. Bhattacharya","doi":"10.5194/nhess-23-2663-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2663-2023","url":null,"abstract":"Abstract. Floods are among the most destructive natural hazards in\u0000the world, posing numerous risks to societies and economies globally.\u0000Accurately understanding and modeling floods driven by extreme rainfall\u0000events has long been a challenging task in the domains of hydrologic science and engineering. Unusual catchment responses to flooding cause great difficulty in predicting the variability and magnitude of floods, as well as proposing solutions to manage large volumes of overland flow. The usage of nature-based solutions (NBSs) has proved to be effective in the mitigation of\u0000flood peak rate and volume in urban or coastal areas, yet it is still not\u0000widely implemented due to limited knowledge and testing compared to\u0000traditional engineering solutions. This research examined an integrated\u0000hydrological and hydraulic modeling system to understand the response of an\u0000at-risk watershed system to flooding and evaluate the efficacy of NBS\u0000measures. Using the Hydrologic Engineering Center Hydrologic Modeling System\u0000and River Analysis System (HEC-HMS and HEC-RAS) software, an integrated\u0000hydrologic–hydraulic model was developed for Hurricane Matthew- (2016) and\u0000Florence-driven (2018) floods across the Little Pee Dee–Lumber River\u0000watershed, North and South Carolina (the Carolinas), US. The focus was on\u0000Nichols, a small town that has disproportionately been impacted by\u0000flooding during these two hurricane events. The present article proposes a methodology for selecting, modeling, and\u0000evaluating the performance of NBS measures within a catchment, which can be\u0000extended to other case studies. Different NBS measures, including flood\u0000storage ponds, riparian reforestation, and afforestation in croplands, were\u0000designed, modeled, and evaluated. Hurricane Matthew's flooding event was\u0000used for evaluating the NBS scenarios given its high simulation accuracy in\u0000flood inundation compared to the less accurate results obtained for\u0000Hurricane Florence. The scenario comparison evidenced that large-scale\u0000natural interventions, such as afforestation in croplands, can reduce the\u0000inundated area in Nichols by 8 % to 18 %. On the contrary, the\u0000smaller-scale interventions such as riparian reforestation and flood storage ponds showed a negligible effect of only 1 % on flood mitigation.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42646069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.5194/nhess-23-2607-2023
Harry Podschwit, W. Jolly, E. Alvarado, A. Markos, S. Verma, Sebastian Barreto-Rivera, Catherine Tobón-Cruz, Blanca Ponce-Vigo
Abstract. Statistical analyses of wildfire growth are rarely undertaken, particularly in South America. In this study, we describe a simple and intuitive difference equation model of wildfire growth that uses a spread parameter to control the radial speed of the modeled fire and an extinguish parameter to control the rate at which the burning perimeter becomes inactive. Using data from the GlobFire project, we estimate these two parameters for 1003 large, multi-day fires in Peru between 2001 and 2020. For four fire-prone ecoregions within Peru, a set of 24 generalized linear models are fit for each parameter that use fire danger indexes and land cover covariates. Akaike weights are used to identify the best-approximating model and quantify model uncertainty. We find that, in most cases, increased spread rates and extinguish rates are positively associated with fire danger indexes. When fire danger indexes are included in the models, the spread component is usually the best choice, but we also find instances when the fire weather index and burning index are selected. We also find that grassland cover is positively associated with spread rates and extinguish rates in tropical forests, and that anthropogenic cover is negatively associated with spread rates in xeric ecoregions. We explore potential applications of this model to wildfire risk assessment and burned area forecasting.
{"title":"Estimating the effects of meteorology and land cover on fire growth in Peru using a novel difference equation model","authors":"Harry Podschwit, W. Jolly, E. Alvarado, A. Markos, S. Verma, Sebastian Barreto-Rivera, Catherine Tobón-Cruz, Blanca Ponce-Vigo","doi":"10.5194/nhess-23-2607-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2607-2023","url":null,"abstract":"Abstract. Statistical analyses of wildfire growth are rarely undertaken, particularly in South America. In this study, we describe a simple and intuitive difference equation model of wildfire growth that uses a spread parameter to control the radial speed of the modeled fire and an extinguish parameter to control the rate at which the burning perimeter becomes inactive. Using data from the GlobFire project, we estimate these two parameters for 1003 large, multi-day fires in Peru between 2001 and 2020. For four fire-prone ecoregions within Peru, a set of 24 generalized linear models are fit for each parameter that use fire danger indexes and land cover covariates. Akaike weights are used to identify the best-approximating model and quantify model uncertainty. We find that, in most cases, increased spread rates and extinguish rates are positively associated with fire danger indexes. When fire danger indexes are included in the models, the spread component is usually the best choice, but we also find instances when the fire weather index and burning index are selected. We also find that grassland cover is positively associated with spread rates and extinguish rates in tropical forests, and that anthropogenic cover is negatively associated with spread rates in xeric ecoregions. We explore potential applications of this model to wildfire risk assessment and burned area forecasting.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48787916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-24DOI: 10.5194/nhess-23-2625-2023
D. Notti, M. Cignetti, D. Godone, D. Giordan
Abstract. The global availability of Sentinel-2 data and the widespread coverage of cost-free and high-resolution images nowadays give opportunities to map, at a low cost, shallow landslides triggered by extreme events (e.g. rainfall, earthquakes). Rapid and low-cost shallow landslide mapping could improve damage estimations, susceptibility models and land management. This work presents a two-phase procedure to detect and map shallow landslides. The first is a semi-automatic methodology allowing for mapping potential shallow landslides (PLs) using Sentinel-2 images. The PL aims to detect the most affected areas and to focus on them an high-resolution mapping and further investigations. We create a GIS-based and user-friendly methodology to extract PL based on pre- and post-event normalised difference vegetation index (NDVI) variation and geomorphological filtering. In the second phase, the semi-automatic inventory was compared with a benchmark landslide inventory drawn on high-resolution images. We also used Google Earth Engine scripts to extract the NDVI time series and to make a multi-temporal analysis. We apply this procedure to two study areas in NW Italy, hit in 2016 and 2019 by extreme rainfall events. The results show that the semi-automatic mapping based on Sentinel-2 allows for detecting the majority of shallow landslides larger than satellite ground pixel (100 m2). PL density and distribution match well with the benchmark. However, the false positives (30 % to 50 % of cases) are challenging to filter, especially when they correspond to riverbank erosions or cultivated land.
{"title":"Semi-automatic mapping of shallow landslides using free Sentinel-2 images and Google Earth Engine","authors":"D. Notti, M. Cignetti, D. Godone, D. Giordan","doi":"10.5194/nhess-23-2625-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2625-2023","url":null,"abstract":"Abstract. The global availability of Sentinel-2 data and the widespread coverage of cost-free and high-resolution images nowadays give opportunities to map, at a low cost, shallow landslides triggered by extreme events (e.g. rainfall, earthquakes). Rapid and low-cost shallow landslide mapping could improve damage estimations, susceptibility models and land management. This work presents a two-phase procedure to detect and map shallow\u0000landslides. The first is a semi-automatic methodology allowing for mapping\u0000potential shallow landslides (PLs) using Sentinel-2 images. The PL aims to\u0000detect the most affected areas and to focus on them an high-resolution mapping and further investigations. We create a GIS-based and user-friendly methodology to extract PL based on pre- and post-event normalised difference vegetation index (NDVI) variation and\u0000geomorphological filtering. In the second phase, the semi-automatic\u0000inventory was compared with a benchmark landslide inventory drawn on\u0000high-resolution images. We also used Google Earth Engine scripts to\u0000extract the NDVI time series and to make a multi-temporal analysis. We apply this procedure to two study areas in NW Italy, hit in 2016 and 2019 by extreme rainfall events. The results show that the semi-automatic mapping based on Sentinel-2 allows for detecting the majority of shallow landslides larger than satellite ground pixel (100 m2). PL density and distribution match well with the benchmark. However, the false positives (30 % to 50 % of cases) are challenging to filter, especially when they\u0000correspond to riverbank erosions or cultivated land.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49126009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-21DOI: 10.5194/nhess-23-2593-2023
M. Morlot, S. Russo, L. Feyen, G. Formetta
Abstract. Heat waves (HWs) and cold waves (CWs) can have considerable impact on people. Mapping risks of extreme temperature at local scale, accounting for the interactions between hazard, exposure, and vulnerability, remains a challenging task. In this study, we quantify risks from HWs and CWs for the Trentino-Alto Adige region of Italy from 1980 to 2018 at high spatial resolution. We use the Heat Wave Magnitude Index daily (HWMId) and the Cold Wave Magnitude Index daily (CWMId) as the hazard indicators. To obtain HWs and CW risk maps we combined the following: (i) occurrence probability maps of the hazard obtained using the zero-inflated Tweedie distribution (accounting directly for the absence of events for certain years), (ii) normalized population density maps, and (iii) normalized vulnerability maps based on eight socioeconomic indicators. The methodology allowed us to disentangle the contributions of each component of the risk relative to total change in risk. We find a statistically significant increase in HW hazard and exposure, while CW hazard remained stagnant in the analyzed area over the study period. A decrease in vulnerability to extreme temperature spells is observed through the region except in the larger cities where vulnerability increased. HW risk increased in 40 % of the region, with the increase being greatest in highly populated areas. Stagnant CW hazard and declining vulnerability result in reduced CW risk levels overall, except for the four main cities where increased vulnerability and exposure increased risk levels. These findings can help to steer investments in local risk mitigation, and this method can potentially be applied to other regions where there are sufficient detailed data.
{"title":"Trends in heat and cold wave risks for the Italian Trentino-Alto Adige region from 1980 to 2018","authors":"M. Morlot, S. Russo, L. Feyen, G. Formetta","doi":"10.5194/nhess-23-2593-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2593-2023","url":null,"abstract":"Abstract. Heat waves (HWs) and cold waves (CWs) can have considerable impact on\u0000people. Mapping risks of extreme temperature at local scale, accounting for\u0000the interactions between hazard, exposure, and vulnerability, remains a\u0000challenging task. In this study, we quantify risks from HWs and CWs for the\u0000Trentino-Alto Adige region of Italy from 1980 to 2018 at high spatial\u0000resolution. We use the Heat Wave Magnitude Index daily (HWMId) and the Cold\u0000Wave Magnitude Index daily (CWMId) as the hazard indicators. To obtain HWs\u0000and CW risk maps we combined the following: (i) occurrence probability maps of the hazard\u0000obtained using the zero-inflated Tweedie distribution (accounting directly\u0000for the absence of events for certain years), (ii) normalized population\u0000density maps, and (iii) normalized vulnerability maps based on eight\u0000socioeconomic indicators. The methodology allowed us to disentangle the\u0000contributions of each component of the risk relative to total change in\u0000risk. We find a statistically significant increase in HW hazard and\u0000exposure, while CW hazard remained stagnant in the analyzed area over the\u0000study period. A decrease in vulnerability to extreme temperature spells is\u0000observed through the region except in the larger cities where vulnerability\u0000increased. HW risk increased in 40 % of the region, with the increase\u0000being greatest in highly populated areas. Stagnant CW hazard and declining\u0000vulnerability result in reduced CW risk levels overall, except for the four\u0000main cities where increased vulnerability and exposure increased risk\u0000levels. These findings can help to steer investments in local risk\u0000mitigation, and this method can potentially be applied to other regions\u0000where there are sufficient detailed data.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42088730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-20DOI: 10.5194/nhess-23-2547-2023
Simon Seelig, T. Wagner, K. Krainer, M. Avian, M. Olefs, K. Haslinger, G. Winkler
Abstract. A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost degradation and drainage network development within the rock glacier initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120 000 m3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. We present a systematic analysis of destabilizing factors to deduce the failure mechanism. The identification and evaluation of individual factors reveals a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of a thermokarst drainage network. Progressively changing groundwater flow and storage patterns within the frozen sediment accumulation governed the slope stability of the rock glacier front. Our results demonstrate the hazard potential of active rock glaciers due to their large amount of mobilizable sediment, dynamically changing internal structure, thermokarst lake development, and substantial water flow along a rapidly evolving channel network.
{"title":"The role of thermokarst evolution in debris flow initiation (Hüttekar Rock Glacier, Austrian Alps)","authors":"Simon Seelig, T. Wagner, K. Krainer, M. Avian, M. Olefs, K. Haslinger, G. Winkler","doi":"10.5194/nhess-23-2547-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2547-2023","url":null,"abstract":"Abstract. A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost degradation and drainage network development within the rock glacier initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120 000 m3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. We present a systematic analysis of destabilizing factors to deduce the failure mechanism. The identification and evaluation of individual factors reveals a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of a thermokarst drainage network. Progressively changing groundwater flow and storage patterns within the frozen sediment accumulation governed the slope stability of the rock glacier front. Our results demonstrate the hazard potential of active rock glaciers due to their large amount of mobilizable sediment, dynamically changing internal structure, thermokarst lake development, and substantial water flow along a rapidly evolving channel network.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41859731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-20DOI: 10.5194/nhess-23-2569-2023
A. Acharya, J. Steiner, K. M. Walizada, Salarpouri Ali, Z. Zakir, A. Caiserman, Teiji Watanabe
Abstract. The cryosphere in high mountain Asia (HMA) not only sustains the livelihoods of people residing downstream through its capacity to store water but also holds the potential for hazards. One of these hazards, avalanches, so far remains inadequately studied, as the complex relationship between climate and potential triggers is poorly understood due to lack of long-term observations, inaccessibility, severe weather conditions, and financial and logistical constraints. In this study, the available literature was reviewed covering the period from the late 20th century to June 2022 to identify research and societal gaps and propose future directions of research and mitigation strategies. Beyond scientific literature, technical reports, newspapers, social media and other local sources were consulted to compile a comprehensive, open-access and version-controlled database of avalanche events and their associated impacts. Over 681 avalanches with more than 3131 human fatalities were identified in eight countries of the region. Afghanistan has the highest recorded avalanche fatalities (1057), followed by India (952) and Nepal (508). Additionally, 564 people lost their lives while climbing peaks above 4500 m a.s.l., one-third of which were staff employed as guides or porters. This makes it a less deadly hazard than in the less populated European Alps, for example, but with a considerably larger number of people affected who did not voluntarily expose themselves to avalanche risk. Although fatalities are significant, and local long-term impacts of avalanches may be considerable, so far, limited holistic adaptation or mitigation measures exist in the region. These measures generally rely on local and indigenous knowledge adapted to modern technologies. Considering the high impact avalanches have in the region, we suggest to further develop adaptation measures including hazard zonation maps based on datasets of historic events and modelling efforts. This should, however, happen acknowledging the already existing knowledge in the region and in close coordination with communities, local government and civil society stakeholders. More research studies should also be attempted to understand the trends and drivers of avalanches in the region.
{"title":"Review article: Snow and ice avalanches in high mountain Asia – scientific, local and indigenous knowledge","authors":"A. Acharya, J. Steiner, K. M. Walizada, Salarpouri Ali, Z. Zakir, A. Caiserman, Teiji Watanabe","doi":"10.5194/nhess-23-2569-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2569-2023","url":null,"abstract":"Abstract. The cryosphere in high mountain Asia (HMA) not only sustains the livelihoods of people residing downstream through its capacity to store water but also holds the potential for hazards. One of these hazards, avalanches, so far remains inadequately studied, as the complex relationship between climate and potential triggers is poorly understood due to lack of long-term observations, inaccessibility, severe weather conditions, and financial and logistical constraints. In this study, the available literature was reviewed covering the period from the late 20th century to June 2022 to identify research and societal gaps and propose future directions of research and mitigation strategies. Beyond scientific literature, technical reports, newspapers, social media and other local sources were consulted to compile a comprehensive, open-access and version-controlled database of avalanche events and their associated impacts. Over 681 avalanches with more than 3131 human fatalities were identified in eight countries of the region. Afghanistan has the highest recorded avalanche fatalities (1057), followed by India (952) and Nepal (508). Additionally, 564 people lost their lives while climbing peaks above 4500 m a.s.l., one-third of which were staff employed as guides or porters. This makes it a less deadly hazard than in the less populated European Alps, for example, but with a considerably larger number of people affected who did not voluntarily expose themselves to avalanche risk. Although fatalities are significant, and local long-term impacts of\u0000avalanches may be considerable, so far, limited holistic adaptation or\u0000mitigation measures exist in the region. These measures generally rely on\u0000local and indigenous knowledge adapted to modern technologies. Considering\u0000the high impact avalanches have in the region, we suggest to further develop adaptation measures including hazard zonation maps based on datasets of historic events and modelling efforts. This should, however, happen acknowledging the already existing knowledge in the region and in close coordination with communities, local government and civil society stakeholders. More research studies should also be attempted to understand the trends and drivers of avalanches in the region.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42505313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-17DOI: 10.5194/nhess-23-2531-2023
Clare Lewis, Tim Smyth, David Williams, Jess Neumann, H. Cloke
Abstract. This paper examines the occurrence and seasonality of meteotsunami in the United Kingdom (UK) to present a revised and updated catalogue of events that have occurred since 1750. Previous case studies have alluded to a summer prevalence and rarity of this hazard in the UK. We have verified and classified 98 events using a developed set of identification criteria. The results have revealed a prominent seasonal pattern of winter events which are related to mid-latitude depressions with precipitating convective weather systems. A geographical pattern has also emerged, highlighting three “hotspot” areas at the highest risk from meteotsunami. The evidence reviewed and new data presented here show that the hazard posed by meteotsunami has been underestimated in the UK.
{"title":"Meteotsunami in the United Kingdom: the hidden hazard","authors":"Clare Lewis, Tim Smyth, David Williams, Jess Neumann, H. Cloke","doi":"10.5194/nhess-23-2531-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2531-2023","url":null,"abstract":"Abstract. This paper examines the occurrence and seasonality of meteotsunami in the\u0000United Kingdom (UK) to present a revised and updated catalogue of events\u0000that have occurred since 1750. Previous case studies have alluded to a summer\u0000prevalence and rarity of this hazard in the UK. We have verified and\u0000classified 98 events using a developed set of identification criteria. The\u0000results have revealed a prominent seasonal pattern of winter events which\u0000are related to mid-latitude depressions with precipitating convective\u0000weather systems. A geographical pattern has also emerged, highlighting three\u0000“hotspot” areas at the highest risk from meteotsunami. The evidence\u0000reviewed and new data presented here show that the hazard posed by\u0000meteotsunami has been underestimated in the UK.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48694563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-14DOI: 10.5194/nhess-23-2505-2023
Max Schneider, F. Cotton, P. Schweizer
Abstract. Probabilistic seismic hazard estimates are a key ingredient of earthquake risk mitigation strategies and are often communicated through seismic hazard maps. Though the literature suggests that visual design properties are key for effective communication using such maps, guidelines on how to optimally design hazard maps are missing from the literature. Current maps use color palettes and data classification schemes which have well-documented limitations that may inadvertently miscommunicate seismic hazard. We surveyed the literature on color and classification schemes to identify design criteria that have empirical support for communicating hazard information. These criteria were then applied to redesign the seismic hazard map for Germany. We established several communication goals for this map, including essential properties about moderate-hazard seismic regions and a critical hazard threshold related to the German seismic building codes. We elucidate our redesign process and the selection of new colors and classification schemes that satisfy the evidence-based criteria. In a mixed-methods survey, we evaluate the original and redesigned seismic hazard maps, finding that the redesign satisfies all the communication goals and improves users’ awareness about the spatial spread of seismic hazard relative to the original. We consider practical implications for the design of hazard maps across the natural hazards.
{"title":"Criteria-based visualization design for hazard maps","authors":"Max Schneider, F. Cotton, P. Schweizer","doi":"10.5194/nhess-23-2505-2023","DOIUrl":"https://doi.org/10.5194/nhess-23-2505-2023","url":null,"abstract":"Abstract. Probabilistic seismic hazard estimates are a key ingredient of earthquake risk mitigation strategies and are often communicated through seismic hazard maps. Though the literature suggests that visual design properties are key for effective communication using such maps, guidelines on how to optimally design hazard maps are missing from the literature. Current maps use color palettes and data classification schemes which have well-documented limitations that may inadvertently miscommunicate seismic hazard. We surveyed the literature on color and classification schemes to identify design criteria that have empirical support for communicating hazard information. These criteria were then applied to redesign the seismic hazard map for Germany. We established several communication goals for this map, including essential properties about moderate-hazard seismic regions and a critical hazard threshold related to the German seismic building codes. We elucidate our redesign process and the selection of new colors and classification schemes that satisfy the evidence-based criteria. In a mixed-methods survey, we evaluate the original and redesigned seismic hazard maps, finding that the redesign satisfies all the communication goals and improves users’ awareness about the spatial spread of seismic hazard relative to the original. We consider practical implications for the design of hazard maps across the natural hazards.\u0000","PeriodicalId":18922,"journal":{"name":"Natural Hazards and Earth System Sciences","volume":" ","pages":""},"PeriodicalIF":4.6,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46764263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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