GeoHazards, Volume 5, Issue 2 (June 2024) – 10 articles

Sentinel-2 data are crucial in mapping flooded areas as they provide high spatial and spectral resolution but under cloud-free weather conditions. In the present study, we aimed to devise a method for mapping a flooded area using multispectral Sentinel-2 data from optical sensors and Geographical Information Systems (GISs). As a case study, we selected a site located in Northern Italy that was heavily affected by flooding events on 3 October 2020, when the Sesia River in the Piedmont region was hit by severe weather disturbance, heavy rainfall, and strong winds. The method developed for mapping the flooded area was a thresholding technique through spectral water indices. More specifically, the Normalized Difference Water Index (NDWI) and the Modified Normalized Difference Water Index (MNDWI) were chosen as they are among the most widely used methods with applications across various environments, including urban, agricultural, and natural landscapes. The corresponding flooded area product from the Copernicus Emergency Management Service (EMS) was used to evaluate the flooded area predicted by our method. The results showed that both indices captured the flooded area with a satisfactory level of detail. The NDWI demonstrated a slightly higher accuracy, where it also appeared to be more sensitive to the separation of water from soil and areas with vegetation cover. The study findings may be useful in disaster management linked to flooded-area mapping and area rehabilitation mapping following a flood event, and they can also valuably assist decision and policy making towards a more sustainable environment. Full article

This study focuses on slope stability and geological hazard analyses at the Italian Paleolithic site of Grotta Paglicci. The site is characterized by a cave that contains rich archaeological and anthropological finds, spanning various Paleolithic periods, and includes faunal remains, lithic artifacts, human burials, ornaments, mobiliary art objects, and unique Paleolithic wall paintings. The study employs a multi-technique approach that includes topographic surveys carried out by the robotic total station and GNSS receivers, photogrammetric acquisitions with an unmanned aerial system, 3D SLAM-based LiDAR mapping, and an engineering geological survey. The collected data allowed for the creation of georeferenced 3D models that were utilized in rock slope stability analysis and modeling. The results of this comprehensive survey highlighted how the bedding and joint discontinuities influence rock stability in both the external and internal areas of the cave. The integrated use of SLAM-based LiDAR and photogrammetry has been proven to be an efficient and essential tool in the evaluation of the structural interactions between the external morphology and the cave, thus allowing the proposal of safety measures that will keep the site accessible for future activities. Full article

This research examines the significance of restoring efficient water management systems in India’s semiarid environment, with special emphasis on the role of traditional irrigation structures, such as tanks, in collecting and storing limited water resources. Assessing the benefits of any restoration program, especially when socioeconomic and environmental benefits are involved, is challenging. In the context of tank rehabilitation, a cost-benefit analysis will be conducted regarding economic and ecological returns in the post-desiltation phase. Since the restoration process requires a significant investment, assessing the project’s viability during the planning stage is better. The present study proposes a novel method to indirectly analyse the cost-benefit of the tank restoration process by correlating run-off and storage capacity of tanks before the planning phase. The Ambuliyar sub-basin, which covers an area of 930 square kilometres in Tamil Nadu, India, comprising 181 tanks (water bodies) of varying sizes and shapes, was taken for this study. This study employed the Soil Conservation Service Curve Number (SCS-CN) method, incorporating factors such as soil type, land cover, land use practices, and advanced remote sensing and Geographic Information System (GIS) tools to simulate surface run-off. Run-off volume and tank capacity were compared for all seasons at the micro-watershed level. The results demonstrated that the run-off volume in each micro-watershed significantly exceeded the tank capacity across all seasons. Even during the summer, the run-off volumes in the micro-watershed were considerably higher than the tank capacity. The findings suggest tank restoration can effectively store run-off and significantly fulfil agricultural and other essential needs throughout the year, thereby improving the local rural economy. This study also highlights the need for periodic maintenance and rehabilitation of these tank systems to retain their functionality. Full article

Desertification processes in arid, semi-arid, and dry sub-humid conditions have been enhanced in recent decades. The geospatial database and associated satellite data can be effectively employed for regional planning to address desertification and land degradation. In this study, the Mediterranean Desertification and Land Use (MEDALUS) model has been used to map environmentally sensitive areas due to desertification in the Satara and Sangli districts of Maharashtra, India. This was achieved by combining Landsat-8 multispectral data, Census data, soil data, and climatic variables like temperature, rainfall, and evapotranspiration. The algorithm of MEDALUS is the geometric mean of four indicators, namely soil quality index (SQI), climate quality index (CQI), vegetation quality index (VQI), and socio-economic quality index (SEQI). The findings indicated that the majority of the study area comes under the potential category of desertification (60.32%) followed by fragile (27.87%) and critical (11.81%). Areas with a high propensity for desertification were found over the low to very low climatic quality and moderate to high soil quality including lower socio-economic quality. The lower socio-economic quality is mainly due to high to very high population density (>100 people/km²), low to moderate illiteracy rate (<16%), and low to moderate work participation rate (<50%) that incentivize unsustainable land use practices. The study provides a valuable tool for understanding and managing natural resources. It offers a detailed analysis of the environmental sensitivity of the study area, taking into account various factors like land use, vegetation cover, slope, and soil erosion potential. The developed comprehensive map of the area helps in identifying the most sensitive regions and developing appropriate conservation strategies. The information obtained from the study can be utilized to develop and implement successful measures to prevent or alleviate desertification, which is crucial for sustaining the health of ecosystems and the welfare of local residents. Full article

Marine geohazards in the Bay of Naples, an eruptive region during the late Quaternary, have been assessed based on both morpho-bathymetric and seismic data. Previously identified areas of high marine hazard with slide potential (northern Ischia slope, Naples canyons, and Sorrento Peninsula–Capri slope) have been confirmed and integrated through the seismo-stratigraphic analysis of selected seismic sections. We evaluated the occurrence of important fossil submarine landslides in the stratigraphic record. Several kinds of submarine landslides have been individuated through morpho-bathymetric and seismic interpretation, including creeping, debris avalanches, and debris flows, among others, often controlled by volcanic eruptions. Submarine landslides of Naples Bay are primary geohazards in the marine and coastal areas, which has been ascertained with significant volcanic and tsunami hazards involving the gulf. Despite previous studies on these topics, much work is still needed to compile a systematic database of the submarine landslides of the Bay of Naples, representing a future step of this research. Full article

The Environmentally Sensitive Areas Index (ESAI) is a comprehensive tool for assessing the susceptibility of areas to desertification. This index analyzes various parameters that are vital for environmental health. Through this index, factors such as human activities, geology, soil quality, vegetation and climate patterns are scrutinized. The analysis assigns weights to each participating factor. Thus, the index is derived from the aggregation of four categories (vegetation, climate, soil quality and management practices), and each of them is independently assessed to understand ecological health. In this way, the level of vulnerability to desertification is effectively measured. The application of the index in Greece (for a period of 20 years, 1984–2004) showed signs of environmental degradation and identified many areas with a high risk of desertification. Notably, there was a substantial increase in cultivated land within rural areas, contributing to shifts in the environmental landscape. Furthermore, this period is distinguished as the driest in the last century, with a peak between 1988 and 1993. The consequential rise in irrigation demand, driven by the simultaneous growth of crops and the intensification of agricultural practices, underscores the intricate interplay between human activities and environmental vulnerability. Full article

A landslide is the movement of rocks, debris, and/or soils down a slope, which often includes falls, topples, slides, flows, and spreads. Landslides, a serious natural hazard to human and human activity, often occur in the coastal and mountainous areas in the United States. Although there are some studies that have explored the landslide probability, which is typically directly modeled by inputting potential environmental variables into statistical regression models, this study designed an alternative geospatial analysis and modeling approach. We first conducted statistical diagnostic tests to examine the significance of potential driving factors including landform, land use/land cover, landscape, and climate. In eastern Tennessee, USA, we first applied the t-test and chi-squared test to select the significant factors driving landslides, including slope, clay percentage in the soil, tree canopy density, and distance to roads, having a p-value of less than 0.05. We then incorporated the four identified significant factors as covariates into logistic regression to model the relationship between these factors and landslides. The fitted logistic model, with a high area under the ROC (AUC) score of 0.94, was then applied to predict landslides and make a regional landslide susceptibility map for eastern Tennessee. The landslide’s potential impacts on eastern Tennessee were also discussed, and implications for local governments and communities for current physical infrastructure protection and new infrastructure development were summarized. Full article

The work detailed here is part of an international initiative on the evaluation of dam safety simulation software for internal erosion performance and best practices. The primary experiments involve simulating uncertainty in the failure events of two dams with two different models: DLBreach and WinDAM C. DLBreach is a physically-based dam/levee breach model developed by Wu. WinDAM C is also a physically based dam breach model capable of analyzing both dam overtopping and internal erosion. The dams selected for the analysis include a 1.3 m high dam tested in the lab and a larger 15.56 m high dam, which suffered a failure in the field. The findings from these experiments are extended with a further analysis on variance, sensitivity, and optimization. Finally, a regression model is trained using the results of these simulators as an inquiry into how well such a system can be captured using machine learning techniques. The results of these experiments, together with the results of the other members of the initiative, improve our understanding of the influences that users bring to using these tools. Full article

During the last 10 kyr, significant subsidence and uplift occurred on Mayotte Island in the Comoros archipelago (Indian Ocean), but the role of volcanic processes in Holocene vertical movements has been neglected in the research so far. Here, we show that an abrupt subsidence of 6–10 m occurred between 9.4 and 10 kyr ago, followed by an uplift of the same amplitude at a rate of 9 mm/yr from 8.1 to 7 kyr ago. A comparison of the relative sea level of Mayotte and a reference sea level curve for the global ocean has been conducted using a modeling approach. This shows that an increasing and decreasing pressure at depth, equivalent to the process caused by a deep magma reservoir (50–70 km), was responsible for ~6–10 m subsidence and 6–10 m uplift, whereas loading by new volcanic edifices caused subsidence during the last few thousand years. Surface movements and deep pressure variations may be caused by pulses from the deep mantle, related to superplume activity, but uncertainties and unknowns about these phenomena are still present and further studies are needed. A better understanding of the volcano-tectonic cycle may improve assessments of volcanic hazards. Full article

This paper delves into the potential advantages of integrating gamification into seismic risk management education, with a specific emphasis on the efficacy of serious games in augmenting the learning process. It offers an illustration of gamification within the framework of a seismic risk preparedness project involving multiple countries, languages, and cultures and across the time of the COVID-19 pandemic. The innovation of this approach largely lies in shifting the focus from competition, which is typical in most games, to collaboration. Three digital serious games were implemented to tackle facets of seismic risk management that are particularly favourable for empowering communities at risk. These games were first used in a hybrid event where students from Algeria, Morocco, and Italy engaged in gameplay both in person within their respective classrooms and remotely with classes in each country. The evaluation study showed the positive impact of gamification in captivating young participants and thereby instilling best practices in seismic risk management. Full article