NH9.9

Single natural hazards, multi-hazards, and anthropogenic processes all contribute to dynamic risk due to the changing nature of the hazard, exposure, and vulnerability over time. Here we discuss the development of dynamic risk scenarios for single and multi-hazards, including multi-hazard interrelationships, in the context of three urban areas, Istanbul, Kathmandu, and Nairobi, all foci of the UK GCRF funded “Tomorrow’s Cities” Research Hub. We first do systematic overviews of multiple sources of evidence (academic and grey literature, online media, social media) to produce a profile of single hazards and multi-hazard interrelationships for each urban area, from which we produce dynamic risk scenarios. Then, we further developed dynamic risk scenarios through co-production with relevant local hazard stakeholders in facilitated workshops and semi-structured interviews in Nairobi and Istanbul. The dynamic risk scenarios include multiple types of single hazards, three different hazard interrelationships (i.e., triggering, increased probability, and compound hazards) and anthropogenic processes. These dynamic risk scenarios are relevant for short-term considerations (e.g., days or weeks, such as an earthquake triggering landslides and blocking rivers) or longer-term (such as climate change influencing the hazard, or anthropogenic processes of urban growth influence the hazard, exposure, and vulnerability). Examples of challenges identified by stakeholders include governance-related issues, such as siloed approaches to hazards which are often single-hazard focused, lack of enforcement of regulations, translation of planning to implementation, centralised policy-making, needs beyond electoral cycles, lack of financial and human resources, and disconnect between scientific and policy-making communities. Other challenges stakeholders identified include a lack of existing data and research in their region on multi-hazard interrelationships, anthropogenic processes and risk, and other components that make up dynamic risk scenarios. Opportunities identified by stakeholders include increased awareness of the factors that might influence risk dynamically in their urban region and integration of these factors into existing urban regeneration project planning. As identified by local stakeholders, these scenarios have a vast array of potential benefits for disaster risk management in their cities, especially in terms of enhanced preparedness and risk-informed planning.

How to cite: Malamud, B. D., Šakić Trogrlić, R., Hussain, E., Thompson, H., Yahya Menteşe, E., Öner, E., Yolcu, A., Mwangi, E., and Gill, J.: Dynamic risk scenarios for single and multi-hazards in the Global South: Nairobi, Istanbul and Kathmandu, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10366, https://doi.org/10.5194/egusphere-egu22-10366, 2022.

Disasters related to hydrological hazards are frequent, occur worldwide, and regularly devastate many African cities. The victims are commonly among the population in precarious situations, without solid infrastructure and with incomes too low to recover from disasters.

Located in the western branch of the East African Rift, and squeezed between the shore of Lake Tanganyika and steep hillslopes, the city of Bujumbura hosts approximately 800,000 people. It is regularly affected by disasters related to lake and river floods, flash floods, riverbank collapses, and gullies. This research aims to assess people's vulnerability to these hydrological processes through the analysis of the territorial vulnerability of the city. To achieve this objective, we present here the first step which focuses on the evaluation of the exposure to past hydrological disasters.

We built a comprehensive dataset using information from different sources, such the Civil Protection, that we combined and complemented with field data collection obtained from qualitative and quantitative surveys. Given the limited information on the susceptibility to the various processes studied, the distribution of past disasters is used as an indicator of the exposure of different parts of the city to hydrological hazards. This phenomenological approach is a key step to map and understand risk due to hydrological hazards.

Between 1990 and 2021, the city recorded more than 210 catastrophic events. Flooding was the most frequent hazard. For example, with a rise of more than 2m above its normal level, the Lake Tanganyika flooding in April 2021 has induced the displacement of many people and the abandonment of many houses and recreation centers. Flash flooding and gullying have been reported mostly at the foot of the hillslopes. The collapse of river banks has also caused severe damages to infrastructures, along the major rivers crossing the city.

Like many African cities, Bujumbura is characterized by the non-compliance with the law, an inefficient drainage system, the anthropization of the hillslopes overlooking the city, the increasing demand for housing and a lack of structure in its urban expansion. The older neighborhoods of central Bujumbura seem adapted to cope with these types of events, while the peri-urban areas are not. The combination of these vulnerability factors makes Bujumbura more exposed to disasters of hydrological origin.

How to cite: Nsabimana, J., Henry, S., Ndayisenga, A., Kubwimana, D., Dewitte, O., Kervyn de Meerendré, F., and Michellier, C.: Exposure to past disasters related to hydrological hazards: the case of Bujumbura city, Burundi, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8091, https://doi.org/10.5194/egusphere-egu22-8091, 2022.

Uvira is a rapidly growing city of about 600,000 inhabitants in DR Congo. Squeezed between the shore of Lake Tanganyika and steep mountains hillslopes, and under the influence of a tropical climate, the city is familiar with flash floods. Nevertheless, the impacts of the flash flood event of April 2020 have been unprecedented in the last decades. Debris-rich flash floods led to at least 43 deaths, nearly 200 injuries, more than 5,500 houses destroyed and at least 70,000 people made homeless. Dozens of socio-economic infrastructures were damaged and nearly 280,000 people were left without hydroelectric power as a result of damage to water and electricity distribution networks in the city. In this work we explore the natural and anthropogenic causes of the exceptional impacts of these flash floods. To do so, we use satellite images, historical aerial photographs, social media reports, field observations, and details provided by local stakeholders and citizen observers. We show that a high-magnitude rainfall event, that occurred at the end of a wetter-than-usual rainy season, triggered, over an exceptionally large area for the region, hundreds of landslides in the upper parts of the watersheds. These landsides transported extra material to the flooded rivers, increasing their sediment content and lateral mobility. We also show that the landscapes of the watersheds where this compound event occurred remained rural in the last six decades and were not impacted by significant forest cover changes and road construction, hence eluding the role of key potential human activities on the magnitude of the flash floods. However, downstream, the city expanded with little consideration of the geomorphological context of the environment where the alluvial fans and flood plains of the rivers have been significantly urbanized in the last decades, often in an informal manner. The impacts of the April 2020 flash flood event are still present almost after two years  and are anticipated to remain at least a few more years; most remarkably, the disturbance of the river dynamics and the severe bank erosion caused by the large supply of sediment. Furthermore, often-uncontrolled sediment mining, seen here by the local people as an opportunity, exacerbates the unpredictable dynamics of the system. In the meantime, flooded areas where houses were destroyed are being resettled. Although authorities and inhabitants are aware of the danger, they face limited means to improve the management and planning of the city.

How to cite: Mugisho Bachinyaga, J., Deijns, A., Ilombe Mawe, G., Kervyn, F., Michellier, C., Mugaruka Bibentyo, T., Nkere Buliba, J., Nzolang, C., Smets, B., and Dewitte, O.: The flash floods of April 2020 in Uvira (DR Congo): story of an event with extreme impacts, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6223, https://doi.org/10.5194/egusphere-egu22-6223, 2022.

Landslides are widespread natural hazards that are responsible for substantial economic and societal damage globally each year. In New Zealand, landslides frequently occur on soil and rock, often triggered by high rainfall and/or seismic activity. This study focuses on the Gisborne district on New Zealand’s North Island. The area is particularly susceptible to landslide hazards due to (1) the region's location on an active plate boundary, (2) steep slopes, (3) relatively young, soft geology, (4) land use change, and (5) extreme rainfall events including landfall of extra-tropical cyclones. The interplay of several of these factors led to a particularly damaging rainfall-induced landsliding event after 4th November 2021, following >200 mm of rain falling in parts of the district over 24 hours. Effects across the region were widespread. Damage to, and evacuation of, residential properties occurred in Gisborne city itself, from shallow rotational slumping and earthflows. The vulnerability of the city’s water supply (via the Te Arai Pipeline) was highlighted by the reactivation of a large complex landslide, that extended to within a few meters of the pipeline. Destruction of the (mothballed) Gisborne-Wairoa railway line occurred near Beach Loop due to reactivation of the Whareongaonga Landslide. Across the Gisborne district, detecting ground deformation related to landslides is vital for identifying and managing areas at risk. Interferometric synthetic aperture radar (InSAR) revealed that many of the landslides that occurred following the November 2021 rainfall event were on slopes that had been actively deforming for several years. Thus, in future, InSAR should prove useful for detecting, mapping and monitoring landslides in the district, and assisting with planning decision-making.

How to cite: Brook, M., Cook, M., and Cave, M.: Infrastructure-damaging landslides from an extreme rainfall event: case study from Gisborne, New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7111, https://doi.org/10.5194/egusphere-egu22-7111, 2022.

The Himalayan State of Sikkim is prone to some of the world's largest landslides which have caused catastrophic damages to lives, properties and infrastructures in the region. The state capital, Gangtok, has experienced rapid population growth over the last decades. The rate of urban expansion has led to encroachment and development on unstable slopes and unplanned construction and frequent violation of building by-laws and regulations. Significant areas of the city experience constant displacement due to the presence of relatively weak rock formations comprising of schists and phyllites. While some urban areas have been completely abandoned due to the structural damages in residential housing, schools, and office buildings, often these buildings are simply repaired or replaced.

Gangtok is draped over several relatively steep hillsides. In this study, we have used synthetic aperture radar interferometry (InSAR) to understand the patterns of displacement better, highlighting areas prone to landslides. The rates of movement of these highly urbanized unstable areas have been measured using data collected by the Sentinel-1 satellites between 2015 and 2021. Field investigations have also confirmed the ongoing ground surface displacements shown in the InSAR results.

Discretely bounded areas in Gangtok are moving at rates sometimes exceeding 12 cm/year. In this study, we concentrate our analysis on three landslide areas where people are residing: Tathenchen, Chanmari and Upper- and Lower-Sichey. In each of these areas, movement is continuous throughout the year. However, distinct periods of acceleration and deceleration are clearly linked to seasonal monsoon rainfall. For example, the velocity of the Upper Sichey landslide varies from about 3 cm/year to 7 cm/year, with peak velocity being reached shortly after peak precipitation each year. In addition, less than half of households in the region are connected to a wastewater network, resulting in significant amounts of water seeping into the local ground.

The type of displacement information obtained by InSAR monitoring is helpful for developing effective mitigation strategies that can limit landslide damage. For example, while rainfall cannot be controlled, better drainage networks can mitigate the local effects. In a broader perspective, the data can be used within urban development planning to identify risk areas and monitor potential zones of catastrophic collapse.

How to cite: Dehls, J. F. and Bhasin, R. K.: Living on landslides: seasonal rainfall effects on rates of movement in highly urbanized unstable areas in Gangtok, Sikkim Himalaya, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1661, https://doi.org/10.5194/egusphere-egu22-1661, 2022.

Mountains socio-ecological system are both complex and vulnerable. Europe’s mountain socio-ecological system have evolved over millennia and continue to adapt to the pressure of a changing climate and to changing societal demands. Scientist and practitioners have now at disposal a number of datasets to better understand socio-ecological dynamics on Europe’s mountain, including the European Settlement Map (ESM), a 2x2  m resolution building map generated for 39 European countries including Turkey (Sabo et al 2021). The map is produced based on very high spatial resolution satellite imagery form a mix of sensors acquired through the European Coperncius program and a combination of ancillary datasets including land use. The 2 x 2 m² spatial resolution map is well suited to study and quantify the presence of buildings in small settlements typical of mountain areas. The settlement map distinguishes between residential and nonresidential buildings. It covers the epoch 2013 and 2018 and thus allows quantifying the change in the building stock between the two epochs. The datasets is particularly suited to assess exposure- and change in exposure - to natural hazards, to assess accessibility and cost of transport. It can be used as a spatial infrastructure to model societal impact on protected areas and on ecosystem services. The map will be combined with population data from censuses to provide insights on depopulation in the more marginal mountain areas of Europe as well as to assess the growth of buildings and infrastructure in the municipality with higher rate of development.  The datasets will be available as open source, and feedback from the mountain community of researcher and practitioners will be welcome to understand the interest for this information and the need for future map updates.

How to cite: Ehrlich, D., Kemper, T., and Sabo, F.: The European Settlement Map. A fine scale European wide building map suited to quantify human presence in mountain areas of Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13072, https://doi.org/10.5194/egusphere-egu22-13072, 2022.

The Urban Geo Footprint (UGF) is a project currently developed in the framework of the EuroGeoSurvey Urban Geology Expert Group (UGEG) and specifically focused on the geo-environmental pressures in urban areas.

The main goal of the study is to set up a classification tool (UGF) aimed to identify the main geological features that could influence and/or interfer with (ongoing) anthropic activities within urban catchments.

The following main drivers are defined in the «UGF framework»: Geology, Climate, Geohazards, Geomorphology, Subsoil anthropic pressure. Each driving factor is articulated in quantitative and indexed (using scores) parameters. At the present early stage all these parameters are going to be indexed and weighted based on two levels of investigation: “basic” and “advanced”. The final result for each city is the “UGF INDEX”  coming from the combination of all the drivers specific scores. The higher the index value, the higher the geotechnical and environmental complexity of the urbanized catchment.

The expected outcomes of the UGF urban areas indexing are:

• A classification of cities according to their geological setting and climatic features, eventually allowing their clustering and supporting sharing of knowledge and capabilities among urban areas.
• Better understanding of geo-environment processes possibly interacting with urban subsurface and ground infrastructures, thus also encouraging and support cities’ subsurface resilience for sustainable (future) growth.
• Help for better assessing the ‘economic’ and ‘social well-being’ benefits (i.e. in terms of ‘geological resilience’) that could derive from urban planning associated to subsoil knowledge.
• A fact-sheet referred to the subsoil of each city, to be progressively updated.

Other objectives of the project are:

• Contributing to develop a method for the comparison of data from different environmental urban contexts.
• Improving the European collaboration and, therefore, the exchange of ideas on good practices to increase urban areas’ resilience.
• Improving citizens' awareness of both the resources and the threats associated with geology.
• Produce a tool for decision makers support (e.g. urban planning, hazards prevention) in order to obtain economical and social well-being benefits.

How to cite: Lentini, A., Benjumea-Moreno, B., Bricker, S. H., Chiessi, V., Xavier, D., Galve, J. P., Giordano, G., Guarino, P. M., Kearsey, T., Leoni, G., Pizzino, L., Puzzilli, L. M., and La Vigna, F.: Clustering urban areas by a geological point of view: The Urban Geo Footprint tool, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12453, https://doi.org/10.5194/egusphere-egu22-12453, 2022.

Children (< 5 years) are highly vulnerable during hot weather, however the impacts of past and future warming on child mortality has never been estimated. Here, we use CMIP6 global climate models to quantify, for the first time, the heat-related child mortality that has already occurred (1995 – 2020) in Africa due to climate change, as well as estimate future burdens (2020 – 2050). By 2009, heat-related child mortality was already double what it would have been without climate change and outweighed any contributions from general improvements in development. Under a high emission scenario (SSP585) mortality will double by 2049 compared to 2005 - 2014. Mitigation will save lives; if 2050 temperature increases are kept to 1.5ºC, approx. 3900 – 6300 children could be saved annually in Africa compared to the SSP585 scenario. Our findings support the need for urgent mitigation and adaptation measures to save lives now and in the future.

How to cite: Chapman, S., Birch, C. E., Marsham, J. H., Part, C., Kovats, S., and Hajat, S.: Past and predicted climate change impacts on heat-related child mortality in Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1640, https://doi.org/10.5194/egusphere-egu22-1640, 2022.

While previous research on historical changes in heat-related mortality observed decreasing trends over the recent decades, future projections suggest increasing impact of heat on mortality in most regions of the world. This study aimed to analyse temporal changes in temperature-mortality relationships in Prague, Czech Republic in the warm season (May-September), using a daily mortality time series from 1982 to 2019. To investigate possible effect of adaptation to increasing temperature, we divided the study period into four decades (1980s–2010s). We used conditional Poisson regression models to identify decade-specific relative risk of heat-related mortality and to calculate the annual number of heat-attributable deaths and the heat-attributable fraction of total warm season deaths. We estimated their trends over the whole study period by a generalized additive model with non-parametric smoothing spline. Our results showed that the unprecedentedly hot 2010s was associated with approximately twice as large relative risk of heat-related mortality than in previous decades. This resulted in the reversal of the trend in heat-attributable mortality in the 1990s and its increase during the last two decades. Our findings highlight the importance of further improvement of adaptation measures such as heat-and-health warning systems to protect the heat-susceptible population.

How to cite: Urban, A., Fonseca-Rodríguez, O., Di Napoli, C., and Plavcová, E.: Temporal changes of heat-attributable mortality in Prague, Czech Republic, over 1982–2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2983, https://doi.org/10.5194/egusphere-egu22-2983, 2022.

The risk of extreme heat mortality is ever increasing with the rapidly changing climate. With the collision of several mega-trends – aging societies, urbanization, inequality – the need for a comprehensive heat mortality risk analysis is growing. Here, we present a probabilistic analysis of the impact of extreme heat on city-scale mortality, demonstrated for more than 750 locations around the world. First results show that heat-related excess mortality of a 100-year summer in the climate of 2000 must be expected roughly every ten to twenty years in today’s climate for most locations.

We produce the probabilistic risk assessment for heat mortality by building on the open-source natural catastrophe risk platform CLIMADA (CLIMate ADAptation). We combine state-of-the-art epidemiological time series analysis methods with single model initial condition large ensemble (SMILE) climate model output. The epidemiological analysis relies on quasi-Poisson regression time series analyses and requires daily city-level mortality data which we have for more than 750 locations through the MCC (Multi-Country Multi-City) Collaborative Research Network database. This analysis results in city-specific risk of exceedance mortality as a function of temperature. The SMILE approach takes a climate model and runs it multiple times with perturbed initial conditions but using the same climate scenario. It thus indicates multiple physically consistent and plausible pathways of the climate which can be used for a probabilistic risk assessment. This allows estimation of tail-risks and quantification of return-period-based mortality impacts. We used SMILE output of seven different climate models, totaling 270 model runs, to estimate impacts and uncertainties of tail risks.

Communicating risk using (shifts in) return periods is helpful to start dialogues with government authorities, city planners and decision makers, as such metrics are commonly used to prepare for natural catastrophes

How to cite: Lüthi, S., Fairless, C., Fischer, E. M., Vicedo-Cabrera, A. M., and Bresch, D. N.: Rapid changes in return periods of heat-related mortality extremes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5183, https://doi.org/10.5194/egusphere-egu22-5183, 2022.

Authors:

Smrati Gupta^1,2*, Yogesh K. Tiwari¹, J. V. Revadekar¹, Pramit Kumar Deb Burman¹, Supriyo Chakraborty¹, Palingamoorthy Gnanamoorthy^3,4

¹Indian Institute of Tropical Meteorology, Pune, Ministry of Earth Sciences, Govt. of India

²Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi, India

³Coastal Systems Research, M. S. Swaminathan Research Foundation, Chennai, India

⁴Key Laboratory of Tropical Forest Ecology, Chinese Academy of Sciences, Menglun, China

Abstract           

A significant amount of the major greenhouse gas, carbon dioxide (CO₂), released into the atmosphere is sequestered by the terrestrial biosphere. Climatic parameters such as temperature, precipitation, soil moisture, etc., modulate this sequestration capacity or sink in varied limits. A little information is available on the impact of extreme temperatures on the terrestrial biosphere sequestration of atmospheric CO₂. This study explores the modulation in the terrestrial sink of CO₂ caused by the frequently occurring extreme temperature phenomenon such as heatwaves over the Indian domain. Heatwaves are extreme temperature phenomena extending from the North-west Indian region towards the south-east region, occurring primarily in the pre-monsoon season of March-May (MAM), sometimes prolonged until June. The high intensity and duration of heatwaves during the season lead to the loss of human work capacity, health, economic losses, and even lives. The year 2015 witnessed one of the dreadful heatwave events in recent years, resulting in the loss of more than 2500 human lives within a season owing to heatwaves. The frequency and intensity of heatwaves are projected to increase further soon globally, including India, in the light of global climate change. It is not only of concern for human resources.

From the biosphere perspective, the terrestrial sink of CO₂ has also been studied to get affected by heatwaves. Temperature is one of the prime factors responsible for photosynthesis and ultimately for the available atmospheric CO₂ fixation by the plants. As such, the CO₂ fixation by the biosphere is affected during MAM season due to limited reduced soil moisture in this hot and dry season, leading to higher atmospheric CO₂ concentrations. In this study, we examine the sub-seasonal variability in the atmospheric CO₂ observed within MAM, driven by subdued fixation by ecosystems in the presence of extreme temperature phenomena like heatwaves. Here, available observations of CO₂ flux or Net Ecosystem Exchange (NEE) flux from MetFlux India Project funded by the Ministry of Earth Sciences, India, studied in conjunction with the retrieved atmospheric and columnar CO₂ concentrations from instruments aboard Atmospheric Infrared Sounder and Orbiting Carbon Observatory-2 satellites during the heatwave period of the year 2015. Our results suggest during a heatwave period, there is an initial increase in carbon uptake by the ecosystem with the temperature rise. But a further rise in temperature after some critical high temperature (~ 32 ͦ C) tends to reduce CO₂ uptake compared to the non-heatwave period of the same season. The satellite retrievals also noticed an increase in atmospheric CO₂ concentrations by 2-3 ppm during the heatwave period. The impact and feedback of heatwaves on the biospheric component of the carbon cycle is one of the significant outcomes of this study.

How to cite: Gupta, S.: A study on the linkage between extreme temperature and atmospheric Carbon dioxide variability over India, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8073, https://doi.org/10.5194/egusphere-egu22-8073, 2022.

Extreme hot-humid heat impacts both urban and rural livelihoods, reducing labor output and damaging health. As such, increasing exposure to hot-humid heat may be reducing food security for both rural and urban household in Africa. Yet, due to a lack of fine-resolution meteorological data, we have a poor understanding of where urban and rural exposure to hot-humid heat is impacting food security across the continent’s diverse geographies. To fill this gap, using more than 20,000 geo-located surveys from the Demographic and Health Survey Program, we map how the spatial relationship between household-level food security and heat exposure has varied among rural and urban populations since the 1980s. We document spatial and temporal heterogeneity, identifying areas of concern where dangerously hot-humid heat is increasingly co-impacting both urban and rural food security outcomes. Given that hot-humid heat waves will worsen across much of Africa as we warm our climate, our results add to growing calls for effective extreme heat warning systems, including seasonal forecasts, tailored to reduce the impacts of hot humid-heat for all people, regardless of where they live.

How to cite: Tuholske, C., Latka, C., Baylis, K., Blekking, J., Green, R., Kim, M., Anderson, P., Caylor, K., and Funk, C.: Extreme heat impacts on food security in Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13336, https://doi.org/10.5194/egusphere-egu22-13336, 2022.