NH9.6

NH9 EDI

The adverse effects of droughts are felt all over the globe, especially in recent years. Droughts often lead to direct and indirect impacts on different sectors from local to global scales. The likelihood of such impacts, understood as drought risk, is caused by the combination of drought hazards, exposure and systems’ vulnerabilities. To support the identification and planning of drought risk reduction and adaptation options, information is needed on the root causes, patterns and dynamics of drought risk and its related impacts. Even though the effects of drought are widespread and well known, research focusing on the different drought risk dimensions lags behind other natural hazard research. Common standards for risk analysis and its components, as well as for impact assessment, are missing. Furthermore, there are no common criteria for assessing the impacts of past and potential future droughts. Whether this is due to the difficulty to grasp the hazard, the lack of standards for vulnerability, exposure and risk assessment, the myriad of different sectors involved, or the complex web of direct and indirect impacts remains unknown so far.
This session addresses drought research beyond the hazard. This includes techniques to collect drought impact information, methods to assess exposure, vulnerability and drought risk for different sectors (e.g. agriculture, forestry, energy production, public water supply, commercial shipping, tourism, wildfires, human health), at different spatial (local to global) and temporal (past trends, current patterns, future scenarios) scales. The session aims to gather examples from around the globe at different scales, discussing best practices, existing challenges and potential ways forward. We welcome the full variety of thematic foci (hazard, exposure, vulnerability, risk, and impact assessment) based on qualitative, quantitative and mixed-methods approaches. The session aims to bring together scientists and practitioners to evaluate the current state-of-the-art, foster drought risk research, establish a community of researchers and practitioners, and shape the future of drought vulnerability and risk research.
The session is closely linked to the NHESS special issue “Drought vulnerability, risk, and impact assessments: bridging the science-policy gap” https://nhess.copernicus.org/articles/special_issue1113.html of which we strongly encourage all session contributors to be part.

Convener: Veit BlauhutECSECS | Co-conveners: Lucia De Stefano, Michael HagenlocherECSECS, Gustavo Naumann, Marthe WensECSECS
Presentations
| Tue, 24 May, 15:55–18:30 (CEST)
 
Room 1.34

Presentations: Tue, 24 May | Room 1.34

15:55–15:58
15:58–16:05
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EGU22-8875
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Virtual presentation
Kelly Helm Smith

Drought has a strong subjective component, incorporating an expectation about how much water there “should” be. Impacts of drought are the downstream effects of a phenomenon that is difficult to bound in space and time, but that propagates through sectors and ecosystems. Data on drought losses with a monetary value, such as commodity crops or energy production, are most readily available. Data on changes to ecosystems and other less coordinated economic activities are harder to find. The Drought Impacts Toolkit (droughtimpacts.unl.edu) curates many sources of drought-impact information. Tools hosted on the site focus on gathering and mapping what people are saying about drought via news stories, social media, crowdsourcing and citizen science. These map layers are independently informative and collectively contribute to a convergence of evidence approach to assessing drought impacts. Each represents a channel of information that captures different sets of motivations and describes drought’s effects at different temporal and spatial resolutions. Quantifying the volume of information on each channel over time -- “chatter” -- provides insight into rising and falling levels of awareness or concern about drought. Analysis of and familiarity with the relationships between what is being said on different channels and at what rates, and how they do and don’t coincide with physical phenomena, is a useful diagnostic approach. It may provide early warning of emerging drought or drought impacts, insights into how people experience the effects of drought from one place to another, underlying vulnerabilities, and potential solutions.

How to cite: Smith, K. H.: Tuning in to drought chatter: Detecting deviation from expectation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8875, https://doi.org/10.5194/egusphere-egu22-8875, 2022.

16:05–16:12
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EGU22-12065
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Presentation form not yet defined
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Natalia Limones, Marthe Wens, Rhoda Odongo, Anne Van Loon, and Hans De Moel

Droughts cause major impacts on the Horn of Africa Drylands (HAD), but the factors that determine the magnitude of these impacts are not well understood. The focus is mostly on socio-economic impacts, but environmental and landscape impacts are often overlooked, in part because they are not always immediate, or their direct or indirect linkage to drought is not apparent. However, drought-induced natural resources and landscape degradation can hinder agricultural activities, livestock farming, tourism, etc., causing socio-economic problems as well. Therefore, it is important to study environmental drought risk and its drivers.

In this research, we adopt a machine learning approach to estimate the chance of experiencing environmental and landscape impacts, specifically: degradation or loss of vegetation cover, significant land-use changes, increased number and severity of fires and poor air quality events related to dust concentration, in Ethiopia, Kenya and Somalia. We will use fast and frugal trees to link accumulated water deficits, calculated using several meteorological and hydrological drought indices, with observational data on past drought impacts on the landscape and the environment. Impacts are detected with high-resolution remote sensing imagery products (Copernicus Global Land Cover Layers, WAPOR, Sentinel-5P NRTI AER AI and several MODIS products, among others), which have the advantage of providing continuous long-term information at large scales.

The applied supervised machine learning approach objectively selects drought hazard indices (including their time and severity thresholds) with the best predictability for observed impacts, capturing the relationships between hazard indices and impacts in the HAD administrative divisions. This modelling approach allows for the identification of region-specific issues while it guarantees comparability. This makes it particularly useful for this case study, as the studied environmental and landscape impacts may be context- or location-specific and could arise from a mixture of different drought types.

The method aims at understanding if, when and how environmental and landscape impacts occur simultaneously or successively and allows us to uncover their interlinkages with each other and with the different drought types.

How to cite: Limones, N., Wens, M., Odongo, R., Van Loon, A., and De Moel, H.: Understanding better the environmental and landscape impacts of drought on the Horn of Africa Drylands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12065, https://doi.org/10.5194/egusphere-egu22-12065, 2022.

16:12–16:19
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EGU22-5841
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ECS
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On-site presentation
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Heindriken Dahlmann, Ruth Stephan, and Kerstin Stahl

Despite their considerable water availability, the European Alps are increasingly affected by droughts. Especially in recent decades, drought impacts have illustrated the regions’ vulnerability, so improved knowledge on the spatial distribution of drought impacts from high elevation headwater regions down to plateau and foothill areas is of tremendous importance. The region has an exceptional data availability including archived drought impact information. It is therefore a good test bed for the often-assumed general hypothesis that drought impacts become more severe downstream. The aim of this study was to investigate whether upstream-downstream differences in the distribution of drought impacts exist in the four major river basins of the European Alps - Rhine, Rhone, Po and Danube. Two different classifications were developed to divide these basins in up- and downstream areas. We based the first classification on the distances to the main sink, and the second classification on human influence. The EDIIALPS database provided quantitative data to analyse the distribution patterns of reported drought impacts from 2000-2020. The results suggest a strong regional variability regarding the temporal and spatial distribution of drought impacts within the individual basins. But they support the general hypothesis: for both classifications the number of drought impacts per area is higher in downstream regions. For the classification based on distances differences are statistically significant for the Rhine and Danube basin. The study provides insight into the spatial distribution of drought impacts in the four major river basins of the European Alps and proves the existence of upstream-downstream asymmetries. The integration of drought indices indicating drought conditions might further explain these differences. Climate change and enhanced cascading effects likely increase these asymmetries and consequently future drought management strategies need to move from emergency actions to better preparedness.

How to cite: Dahlmann, H., Stephan, R., and Stahl, K.: Upstream-downstream asymmetries of drought impacts in major river basins of the European Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5841, https://doi.org/10.5194/egusphere-egu22-5841, 2022.

16:19–16:26
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EGU22-4218
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ECS
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On-site presentation
Anastasiya Shyrokaya, Giuliano Di Baldassarre, Gabriele Messori, Ilias Pechlivanidis, Florian Pappenberger, and Hannah Cloke

Despite the scientific progress in drought forecasting, it remains challenging to accurately predict the corresponding impact of a drought event. This is due to the unexplored relationships between (multiple) drought indicators and the impacts across spatiotemporal scales. In this study, we unravel these relationships by analysing the impacts of the severe 2018-2019 drought event in Central Europe. We calculated the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evaporation Index (SPEI) over various accumulation periods, and related the indicators to losses from the European Drought Impact Report Inventory (EDII)1 with a focus on agriculture and water supply. An initial assessment was performed by correlating monthly time series of the drought indicators and the impact data at the EU NUTS1 region level. We further used a Random Forest Model to measure the predictive power of the drought indicators for those impacts.

Our findings reveal significant relationships between the drought indicators and the impacts over different accumulation periods. The analysis also detects region-specific and time-variant differences during the 2018–2019 Central European drought event. As such, our work provides a new framework to unravel the drought indicators-impacts dependencies. In addition, it emphasizes the need to leverage available impact data to increase the capacity to forecast the drought impacts.


1 Last retrieved January 2022

How to cite: Shyrokaya, A., Di Baldassarre, G., Messori, G., Pechlivanidis, I., Pappenberger, F., and Cloke, H.: Comparing drought indicators and negative impacts for the 2018–19 Central European drought event, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4218, https://doi.org/10.5194/egusphere-egu22-4218, 2022.

16:26–16:33
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EGU22-11138
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ECS
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Highlight
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Presentation form not yet defined
David W. Walker, Noemi Vergopolan, Louise Cavalcante, André Almagro, Tushar Apurv, Daniel G. Kingston, Tirthankar Roy, Kelly Helm Smith, and Niko Wanders

The term ‘flash drought’ has become increasingly prevalent in scientific discourse and research on the topic is growing. The corresponding increase in flash drought publications typically presents definitions, mechanisms, detection and monitoring, and forecasting. However, many aspects of flash droughts are less well understood, such as flash drought impacts, especially the socioeconomic and environmental impacts.

Flash droughts tend to be defined from a hydrometeorological perspective as events of rapid onset, rapid intensification, low precipitation and soil moisture, and high temperature. Yet there are similar, often locally named, phenomena around the world with their own specific characteristics and impacts that could be considered flash droughts. Such events may not match literature or index-specific definitions of flash drought, for example due to their very short duration or anthropogenic drivers. Consequently, they may go undetected or unpredicted in the increasingly common global flash drought products and may not be considered in flash drought research.

We, the co-authors (a sub-section of the Panta Rhei ‘Drought in the Anthropocene’ working group), conducted a survey among peers to collect cases from around the world of alternative names, characteristics and impacts of flash droughts. Many regions were represented in the responses and local nomenclature for flash drought-like events were identified, in particular from Brazil, South Asia, Sub-Saharan Africa and Central America.

Maps of flash drought hotspots based on hydrometeorological indices often do not indicate whether anything adverse was experienced on the ground, or overemphasise occurrence where events are unlikely. Therefore, we utilised the survey findings and subsequent investigations to ‘ground truth’ a flash drought hotspots map. We related hotspots to published case studies of drought impacts or existence of local terms for flash droughts. However, mismatches occurred suggesting there are regions potentially experiencing flash droughts that are either not represented in our survey nor in the literature or there are inaccuracies in flash drought hotspot identification.

How to cite: Walker, D. W., Vergopolan, N., Cavalcante, L., Almagro, A., Apurv, T., Kingston, D. G., Roy, T., Smith, K. H., and Wanders, N.: Flash droughts: bridging the understanding between physical definitions and societal impacts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11138, https://doi.org/10.5194/egusphere-egu22-11138, 2022.

16:33–16:40
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EGU22-511
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ECS
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On-site presentation
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Jan Sodoge, Mariana Madruga de Brito, and Christian Kuhlicke

Droughts are expected to increase both in terms of frequency and magnitude across Europe. While they impose diverse impacts on social-ecological systems, most impact assessments focus on particular sectors or economic aspects. Existing multi-sectoral datasets are limited in spatio-temporal homogeneity and scope due to the manual extraction of impacts from text-based sources. To address this, we developed a novel method for the automatized detection of drought impacts based on newspaper articles. By employing natural language processing and machine learning models, our method is able to extract different classes of drought impacts (e.g. agriculture, forestry, livestock) and their geographic and temporal scope from text data. We applied this method to generate a multi-sectoral dataset of drought impacts in Germany between 2000 and 2021. About 41121 articles from different journals were considered. Accuracy levels of 92-96% per impact class were obtained for the automatic classification of the impacts when evaluated on a human-annotated dataset. For validation against independent data, first results show that our method can replicate both temporal and spatial trends. Our approach advances existing techniques because it (1) requires a significantly lower workload, (2) allows addressing large amounts of data, (2) reduces subjectivity and human bias, and (4) is generalizable to other hazard types as well as text corpora while achieving sufficient levels of accuracy. The findings highlight the applicability of natural language processing and machine learning to create comprehensive impact datasets. Furthermore, the generated information can be used for validating drought risk assessments and impact models.

How to cite: Sodoge, J., de Brito, M. M., and Kuhlicke, C.: Automatized drought impact detection from newspaper articles using natural language processing and machine learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-511, https://doi.org/10.5194/egusphere-egu22-511, 2022.

Coffee break
17:00–17:07
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EGU22-10959
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ECS
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Virtual presentation
Chang-Kyun Park and Jonghun Kam

Effective Drought Index (EDI) was proposed to monitor daily propagations of an emerging drought. The EDI, like other drought indices, uses the last 30 years of the daily precipitation record for the reference period for effective precipitation (EP) climatology, resulting that the drought characteristics can be solely estimated by a recent climatology. To overcome this weakness, this study proposes a self-calibrating EDI, a modified EDI with time-varying EP climatology via the 30-year moving time windows. In this study, the scEDI is calculated from the 240-year daily precipitation records (1777–2020) in Seoul, the south Korean Peninsula, and is compared with and the EDIs with different reference periods. The scEDI successfully adapts multi-decadal variability of precipitation, leading to robust (temporally consistent) estimates of drought severity while the EDIs, particularly with the 1885–1915 (dry) and 1990–2020 (wet) reference periods, over- and under-estimate drought severity, respectively. Furthermore, the droughts estimated by the scEDI are compared with the drought damage records in the Annals of the Joseon Dynasty (1778–1907) and the recent search frequency about droughts in Google and NAVER portals (2016–18) to investigate scEDI threshold values that is linked to actual socioeconomic impacts or favorable drought stages for a high level of drought awareness. Results confirmed that -1.0  and -2.0 of the scEDI can be good threshold values to detect severe droughts that cause socioeconomic impacts for agrarian and industrial societies, respectively. It is also found that the persistent and recovery stage of recent droughts surged the Internet search activities while public interest in drought was low during the onset stage. The findings of this study suggest that the importance of self-calibrating on improving the EDI-based drought assessment.

How to cite: Park, C.-K. and Kam, J.: Impact of Self-Calibrating on the Effective Drought Index: A Case Study of the south Korean Peninsula, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10959, https://doi.org/10.5194/egusphere-egu22-10959, 2022.

17:07–17:14
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EGU22-11185
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ECS
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Presentation form not yet defined
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Silvia Cocuccioni, Ruth Stephan, Stefano Terzi, Mathilde Erfurt, Kerstin Stahl, and Marc Zebisch

Recent drought events highlighted the vulnerability of the European Alps to unexpected conditions of reduced water availability. The drought conditions led to a wide range of impacts especially affecting agriculture. Impacts were not only triggered by the natural hazard itself but also by the level of regional exposure and vulnerability. Nevertheless, the characterization of the exposure and vulnerability in risk assessments still represents a challenging task due to the specific knowledge needed to depict regional conditions and its sparse quantitative high resolution data.

Our study aims to identify the main indicators affecting vulnerability and explore their contribution to the final drought risk in agriculture. We selected the Podravska region in Slovenia and the Thurgau canton in Switzerland. Both are case studies of the Alpine Drought Observatory Interreg project due to recent drought impacts in agriculture. 

Overall, a total of 31 indicators describing vulnerability to agricultural drought impacts was identified by local experts with 12 common indicators for both study areas. The majority of the indicators was solely identified for either Thurgau or Podravska demonstrating each region's specific characteristics. The indicators covered a broad range of aspects, such as geographic conditions (e.g. elevation, south facing), hydrological aspects (e.g. distance to large water bodies), soil characteristics (e.g. water holding capacity), agricultural practices (e.g. intensive farming), agricultural infrastructure (e.g. irrigation infrastructure), farmers' education, and policies (e.g. compensations). For each indicator we collected quantitative spatial data, removing those for which no information was available. Moreover, we normalized the selected indicators and combined them into final regional maps following two weighting scenarios: the equal weighting scenario, with all indicators having the same weight and the expert weighting scenario, where weights were assigned by the involved experts. In the Thurgau case the experts assigned more weights to the indicators related to the soil characteristics (e.g. “water holding capacity” and “humus content”) while for the Podravska case indicators related to farms position and type (e.g. “accessibility to local food market” and “farm diversification”). Final vulnerability maps for the two weighting scenarios and case studies will provide insights into the main vulnerability hotspot to drought, highlighting the main contributing indicators as well as those indicators initially identified by the experts for which no regional data is available.

Overall, this study highlighted the need of integrating the widely used equal weighting scenarios with qualitative knowledge and narratives from key experts. This approach can improve the understanding of agricultural vulnerability assessments to drought events supporting the implementation of adaptation strategies and plans in the Alpine region.

How to cite: Cocuccioni, S., Stephan, R., Terzi, S., Erfurt, M., Stahl, K., and Zebisch, M.: An agricultural vulnerability assessment to droughts in the Alps: exploring indicators’ contributions at regional level, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11185, https://doi.org/10.5194/egusphere-egu22-11185, 2022.

17:14–17:21
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EGU22-11237
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Virtual presentation
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Hossein Aghighi, Abdolreza Ansari Amoli, and Ernesto Lopez-Baeza

A drought risk map has been prepared at the national scale using remote sensing satellite data in Iran by combining output layers resulted from three main components of a risk evaluation procedure including Hazard Quantification (HQ), Vulnerability Assessment (VA) and Identification of Elements at Risk (IER). In this respect, Drought Severity (DS) using the Normalized Difference Vegetation Index (NDVI), Iran land-cover classification map, Iran slope map, population density and irrigated farm percentage in each province are the layers that have been utilised within a Drought Risk Evaluation (DRE) process. The final risk map demonstrates that the north west of the country with a climate corresponding to central European weather conditions has the maximum quantity of drought risk, and the areas with the arid climate mainly located in the middle of Iran have the least amount of drought risk value. The outputs of this research assimilated with the results of a Drought Risk Analysis (DRA) prepared by other disciplines will provide a list of advices to help decision makers to reduce drought risk consequences. Adding other significant satellite data such as precipitation, temperature, soil moisture, drainage density and ground water table will enable researchers to evaluate and map drought risk more accurately.

How to cite: Aghighi, H., Ansari Amoli, A., and Lopez-Baeza, E.: Drought Risk Mapping in Iran Using Remote Sensing Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11237, https://doi.org/10.5194/egusphere-egu22-11237, 2022.

17:21–17:28
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EGU22-249
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ECS
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Virtual presentation
Sahana Venkataswamy and Arpita Mondal

Changes in climate and socio-economic conditions can induce water stress and threaten water security. India is an agriculture-dependent, densely-populated country undergoing rapid societal developments. For proper mitigation and adaptation planning in India, it is, therefore, important to assess how drought hazard, vulnerability and risk would evolve in future. Earlier studies present projected drought risk over India based on frequency analysis and/or hazard assessment alone. This study investigates future evolution of drought risk integrating vulnerability and hazard information at a country-wide scale under the mitigation (RCP2.6) and medium stabilization (RCP6.0) climate scenarios in combination with Shared Socio-economic Pathway middle-of-the-road (SSP2) socio-economic condition. A multivariate standardized drought index (MSDI) based on joint deficits of precipitation and soil moisture is chosen to characterize droughts. Drought vulnerability is assessed by the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method, a robust multi-criteria decision-making technique, considering indicators that represent exposure, adaptive capacity and sensitivity.  Though there is a reduction in areal extent of high or very high drought hazard classes in the country by approximately 7% in future, possibly due to projected rise in precipitation, the area under high or very high drought vulnerability classes increases by 33% in the worst-case scenario. Parts of West Rajasthan, Odisha, Haryana and West Uttar Pradesh are found to be high risk under all scenarios. Bivariate choropleth plots show that future drought risk is more significantly driven by changes in vulnerability resulting from societal developments rather than climate-induced changes in drought hazard. The present study can aid the administrators, policy makers and drought managers in formulating decision support systems for effective drought management.

How to cite: Venkataswamy, S. and Mondal, A.: Evolution of multivariate drought hazard, vulnerability and risk in India under climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-249, https://doi.org/10.5194/egusphere-egu22-249, 2022.

17:28–17:35
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EGU22-5136
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Virtual presentation
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Raphael Neukom, Veruska Muccione, Nadine Salzmann, Christian Huggel, Vincent Roth, and Roland Hohmann

Cumulative extreme events pose substantial risk to society and nature, as they can propagate through various socio-economic systems via process cascades. Adaptation to future climates requires estimations of the likelihood and possible combined impacts of cumulating meteorological/climatic extremes events. Due to the very rare occurrence of low probability events, such estimations remain challenging.

In response to this knowledge gap, a collaborative effort of academic and government institutions at different administrative levels is undertaken. It aims at analysing the potential of such cumulative, complex risks and to suggest actions needed to manage them in Switzerland. The project is based on two case studies, which were developed in collaboration with stakeholders from science, policy making and practice at the national and sub-national level. The case studies assess rare but plausible combined risks of extreme drought events and other meteorological extremes, e.g. heat, as projected by the recently published Swiss Climate Scenarios CH2018. One case study is conducted in the alpine region of southern Grisons, the second one in the urban area of Basel.

Currently, there are only limited approaches available to quantitatively model the manifold cascading effects that may propagate through natural and human systems after the occurrence of combined drought-related extremes. We therefore adapt methods from the field of civil protection and use expert knowledge to develop impact storylines and estimate probabilities and magnitudes of adverse effects on societies and ecosystems.

To estimate the feasibility of a combined drought event leading to the loss of the protective function of forests in the southern Swiss Alps (case study 1), we developed an extensive expert survey. 29 experts from science, administration and practice provided quantitative estimates of drought thresholds and damage probabilities. The survey was split into a top-down and a bottom-up approach, allowing to characterize the possible impacts from two different angles and thereby also assess the robustness of the results.

In contrast, urban areas consist of diverse interlinked systems with very different characteristics, which does not allow to assess impact cascades with a single expert survey. Instead, we used a three-step approach based on semi-quantitative storylines informed by literature and expert interviews. In a first step, experts for individual systems, such as water, transport or health were interviewed about possible weaknesses and blind-spots with regard to the trigger-event. Second, we characterized possible storylines of impact cascades using process diagrams along with quantitative estimates of drought related variables such as river discharge, air and water temperature. In a third step, the plausibility of these storylines was discussed once more with the experts. We report on the advantages and challenges of our approach compared to traditional modelling-based methods in light of transformative adaptation measures to future climates.

How to cite: Neukom, R., Muccione, V., Salzmann, N., Huggel, C., Roth, V., and Hohmann, R.: Tailored approaches to analyse cumulative drought-related climate risks and associated impact cascades in Switzerland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5136, https://doi.org/10.5194/egusphere-egu22-5136, 2022.

17:35–17:42
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EGU22-141
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ECS
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Highlight
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On-site presentation
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Tristian Stolte, Hans de Moel, Marthe Wens, Elco Koks, Felix van Veldhoven, Snigdha Garg, Neuni Farhad, and Philip Ward

This study aims to assess current and future global hydrological drought risk for 263 cities around the globe. Preliminary results among 98 cities show that around 73% of them will likely experience an increase in drought costs in the coming decades. Furthermore, they show that current drought costs are on average between USD 8,000 – 32,000 per 1000 citizens per year, which could increase to approximately USD 9,000 – 40,000 by 2050.  Not many studies have focussed on drought risk at the global scale before, and even fewer explicitly consider cities. However, drought events can have profound impacts on urban areas, as is illustrated by past events like those in Cape Town (2015-2018) and São Paolo (2014-2015). Although research has been done on such specific events, their individual results are often difficult to compare. Therefore, we try to enable that comparison by performing a global urban drought risk assessment, which reveals hotspots of urban drought risk and potentially even puts drought risk on the agenda for cities that are not yet aware of the risks they face. In our approach, we focus on hydrological drought, which is the drought type that most directly affects urban water resources. We link surface-water availability with urban-water withdrawals in the water-source locations of the cities, while taking into account water stress and environmental flow requirements. The hazard is dynamic in time, and future scenarios are based on a selection of RCPs. Exposure is represented as the total population in each city, and evolves over time as well, based on several SSPs. From the hazard and exposure, we use global estimates of freshwater replacement costs to calculate drought cost ranges for each city. We also qualitatively add vulnerability by overlaying the cost ranges with several vulnerability indicators to provide bivariate maps of risk for each city. In addition, attempts are made to verify the results with city practitioners as well as to identify several transformative adaptation options for cities.

How to cite: Stolte, T., de Moel, H., Wens, M., Koks, E., van Veldhoven, F., Garg, S., Farhad, N., and Ward, P.: Global urban drought risk, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-141, https://doi.org/10.5194/egusphere-egu22-141, 2022.

17:42–17:49
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EGU22-2675
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ECS
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On-site presentation
Lorenzo Villani, Giulio Castelli, Luigi Piemontese, Daniele Penna, and Elena Bresci

Droughts have huge negative impacts on livelihoods and economies throughout the world, and climate change is expected to increase their future frequency and severity. For an effective drought management, drought risk assessment is considered of major importance. However, despite the high number of studies, shared and clear guidelines to perform drought risk assessments are missing, undermining the overall reliability of this procedure. A significant limitation common to most drought risk assessments is the lack of any form of validation. Moreover, checking the robustness of the assessment tools is of paramount importance, but appropriate data are usually not available for external validation; hence, internal validations are in many cases the only option. For this scope, we propose a simple but robust uncertainty analysis, using the methodology presented in the “Handbook on constructing composite indicators” of OECD (2008). An additional deficiency of most drought risk assessments is the missing link between the results and possible adaptation strategies. To address this limitation, we propose to use archetype analysis, which is an emerging approach for identifying recurrent patterns within cases and supporting a context-specific generalization of insights.  

The innovations introduced were applied to a drought risk assessment performed for the agricultural systems of five coastal watersheds of central and southern Tuscany, Italy. These watersheds are particularly prone to drought impacts because of the high concurrent water demand for domestic and agricultural uses during the summer months. To allow a better discretization, municipalities were selected as units of analysis. A total of 42 indicators were used to represent drought hazard, exposure, and vulnerability. Multiple drought hazard indicators were selected to estimate both past and future drought hazards, using ready-to-use data from public institutions. Overall, the southern part of Tuscany showed to be the most at risk, in particular the Grosseto province. For the robustness evaluation, we (1) excluded individual exposure and vulnerability indicators, (2) included the excluded indicators with the multicollinearity analysis, (3) assigned different weights, and (4) used an alternative aggregation method to calculate the composite risk indicator. Results in terms of average shifts in rankings and new rankings assigned revealed that the most uncertain parts were the selection of exposure indicators and the assignment of weights, but overall, the rankings were confirmed. The archetype analysis yielded as result seven clusters of municipalities; their characteristics were analysed and tailored adaptation strategies were proposed according to their specific drought risk profiles.

How to cite: Villani, L., Castelli, G., Piemontese, L., Penna, D., and Bresci, E.: Introducing robustness evaluation and archetype analysis in drought risk assessments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2675, https://doi.org/10.5194/egusphere-egu22-2675, 2022.

17:49–17:56
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EGU22-12922
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ECS
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Virtual presentation
Sarra Kchouk, Germano Ribeiro Neto, Louise Cavalcante, Lieke Melsen, David Walker, Rubens Sonsol Gondim, and Pieter van Oel

The different existing frameworks of Water Accounting (WA) techniques have proven to be useful tools for managing water in situations of water scarcity. The indices derived from WA procedures typically focus at informing decisions related to two different targets. A first group focuses on estimating water availability in different parts of a river basin. A second group focuses on the effects of human activities (interventions) on the water balance. Both are precious tools for decision making when the water is even scarcer, like in drought situations. However, their frameworks remain limited for an application to drought and drought impacts as it eludes many specificities proper to droughts. The aim of our study is to explore how WA techniques and indices can thus be adapted for integrated drought management. We based our approach on the water-balance data from the Banabuiú River Basin located in the semi-arid and drought-prone Northeast of Brazil. This area is the place of varied agricultural activities, rainfed or irrigated from a dense network of reservoirs. Droughts, from flash droughts to sometimes pluriannual, can affect the water balance of those reservoirs and the basin, and pose a challenge to meet all the agricultural needs. We direct our results towards the investigation of spatiotemporal scale issues. Indeed, water balance assessments often do not consider spatial variations in a river basin area and only report average annual situations. However, the duration of droughts or their impacts can extend beyond this reference period until sometimes becoming persistent to the system. The same applies for spatial-scale issues. Actions and processes happening at different physical scales and levels, inside and outside the basin, can modify the water balance. By addressing these spatiotemporal complexities, we aim to develop indices that will account for the human activities and enable to better inform decisions for integrated drought management.

How to cite: Kchouk, S., Ribeiro Neto, G., Cavalcante, L., Melsen, L., Walker, D., Sonsol Gondim, R., and van Oel, P.: Accounting for spatiotemporal complexities of drought in water accounting to inform integrated drought management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12922, https://doi.org/10.5194/egusphere-egu22-12922, 2022.

17:56–18:03
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EGU22-3438
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ECS
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On-site presentation
Niko Wanders, Jannis Hoch, Sophie de Bruin, Rens van Beek, Halvard Buhaug, and Nina von Uexkull

In the past decade, several efforts have been made to project armed conflict risk into the future. However all of these approaches neglected the impact of hydrological extremes, specifically drought, on potential conflicts. This study broadens current approaches by presenting a first-of-its-kind application of machine learning (ML) methods to project sub-national armed conflict risk over the African continent along three Shared Socioeconomic Pathway (SSP) scenarios and three Representative Concentration Pathways towards 2050 including hydrological feedbacks.

We specifically assessed the role of hydro-climatic indicators as drivers of armed conflict. Overall, their importance is limited compared to main conflict predictors but results suggest that changing climatic conditions may both increase and decrease conflict risk, depending on the location: in Northern Africa and large parts of Eastern Africa climate change increases projected conflict risk whereas for areas in the West and northern part of the Sahel shifting climatic conditions may reduce conflict risk.

With our study being at the forefront of ML applications for conflict risk projections, we identify various challenges for this arising scientific field. A major concern is the limited selection of relevant quantified indicators for the SSPs at present. Specifically, the links between drought and conflicts are mostly region specific and not necessarily well reflected in the available data. Nevertheless, ML models such as the one presented here are a viable and scalable way forward in the field of armed conflict risk projections, and can help to inform the policy-making process with respect to climate security under changing hydroclimatic conditions.

How to cite: Wanders, N., Hoch, J., de Bruin, S., van Beek, R., Buhaug, H., and von Uexkull, N.: Unravelling the complex interplay between drought and conflict, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3438, https://doi.org/10.5194/egusphere-egu22-3438, 2022.

18:03–18:10
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EGU22-1958
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Presentation form not yet defined
Ying Yao

Drought is one of the most complex hydrological and climate disasters, causing damage to ecosystem structure and function. Ecosystem resilience is considered a key concept for understanding and describing the response of ecosystems to drought. Recovery time, as an important measure of resilience, has been widely used to assess ecosystem resilience to drought, but there is a deficiency in distinguishing the difference in recovery time under various drought intensities. On the basis of the existing assessment of drought resilience based on recovery time, we defined a new resilience indicator using an exponentially fitted curve to characterize the relationship between drought intensity and the corresponding recovery time, and the resilience was quantified by the curve area. Resistance represents the capacity of ecosystems to remain stable during droughts, and we quantified the resistance indicator by the ratio of the frequency of no vegetation loss during drought to drought frequencies. Our results showed that the ecosystem resilience to drought increased from arid to sub-humid regions in China’s dryland, and resistance was the lowest in the semiarid region. There was a trade-off between resilience and resistance: grassland had higher resilience and lower resistance than forestland. Drought memory contributed to the high resilience in the case of high drought frequency. These findings enriched the identification of the resilience of ecosystems to drought and the relationship between resilience and resistance and drought frequency in drylands.

How to cite: Yao, Y.: Evaluation of ecosystem resilience to drought based on drought intensity and recovery time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1958, https://doi.org/10.5194/egusphere-egu22-1958, 2022.

18:10–18:17
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EGU22-11831
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ECS
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Virtual presentation
Miao Zhang and Xing Yuan

The increasing drought with rapid onset in a warming climate arouses wide concerns due to its enormous impacts on the terrestrial ecosystem. Despite the duration of flash drought is relatively short ranging from several weeks to months, its legacy effects on the terrestrial ecosystem may remain even after flash drought. Here we use remote sensing observations of Solar-Induced chlorophyll Fluorescence (SIF) and Gross Primary Productivity (GPP) and a land surface model to investigate the negative impacts and legacy effects of flash drought on terrestrial ecosystem productivity. The decline and recovery in observed and modeled terrestrial ecosystem productivity caused by flash drought are more rapid over drier regions, showing lower drought resistance and higher drought recovery. For wetter regions, GPP and SIF over wetter regions show higher drought resistance, whereas they are still lower within 15 days after flash drought compared with their pre-drought level. The resistance of terrestrial ecosystem productivity shows a significant increasing trend during recent decades, which is possibly related to the increased vegetation growth. The legacy effects of flash drought over wetter regions highlight the importance of drought monitoring and forecasting over humid or semi-humid regions

How to cite: Zhang, M. and Yuan, X.: Response and recovery of terrestrial ecosystem productivity to flash drought over China under climate change, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11831, https://doi.org/10.5194/egusphere-egu22-11831, 2022.

18:17–18:24
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EGU22-12278
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Highlight
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On-site presentation
Lucy Barker, Nathan Rickards, Sunita Sarkar, Jamie Hannaford, Eugene Magee, and Gwyn Rees

Droughts are known to be one of the most damaging and costly natural hazards as a result of their large spatial scale, creeping nature and long duration. They have widespread primary and secondary impacts, and as such, proactive drought management is crucial to mitigate those impacts. In order to do so, it is crucial to understand the drought risk in terms of the characteristics of the drought hazard, who or what is exposed to the drought hazard, and who (or what) is vulnerable to the effects of drought. Drought mitigation, adaptation and management was adopted as one of five strategic objectives under the United Nations Convention to Combat Desertification (UNNCD) 2018-2030 Strategic Framework. Country Parties to the UNCCD agreed a monitoring framework and a range of indicators in order to track progress towards this objective.

Here we present new guidance created to help Parties to the UNCCD report on their progress towards Strategic Objective 3 ‘To mitigate, adapt to, and manage the effects of drought in order to enhance resilience of vulnerable populations and ecosystems’. Progress is monitored using three indicators, characterising the three fundamental components of risk: drought hazard, exposure to drought and vulnerability to drought. The three indicators, as agreed by Parties to the UNCCD, are:

  • Trends in the proportion of land under drought over the total land area,
  • Trends in the proportion of the total population exposed to drought, and
  • Trends in the degree of drought vulnerability.

Acknowledging the need for global applicability, the methods recommended to calculate these three indicators balance state-of-the-art science with relative simplicity, whilst also meeting the requirements set out in official UNCCD Decisions, guidelines of the World Meteorological Organization, and where possible utilising datasets used for other reporting activities (e.g. the Sustainable Development Goals).

The recommended methods for each indicator are illustrated using contrasting case studies from the UK and Thailand, utilising the recommended globally available datasets to calculate the three indicators listed above. In-country data are also used, where available, to calculate the indicators, highlighting the benefits of increased spatial resolution, and/or sensitivity to assessing changes in drought hazard, exposure or vulnerability over time. Finally, opportunities for the future of national reporting on drought risk are discussed.

How to cite: Barker, L., Rickards, N., Sarkar, S., Hannaford, J., Magee, E., and Rees, G.: Supporting national reporting of drought hazard, exposure and vulnerability to track progress in drought adaptation, mitigation and management, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12278, https://doi.org/10.5194/egusphere-egu22-12278, 2022.

18:24–18:30