Natural Hazards Research最新文献

Following the 2018 Palu tsunami event in Central Sulawesi, Indonesia, the geological evidence of paleotsunami in Palu, was investigated to extend the historical record of past tsunamis in this area. A geological survey was conducted in Talise Beach, Palu City, at the southern end of Palu Bay. The stratigraphy sequence from the outcrop profile in Talise Beach showed three clear paleotsunamis. These paleotsunamis are distributed widely and can be traced along 1 ​km parallel to the beach, and each layer is characterized by poorly sorted sand deposited on the paleosoil. The boundary between the sand layers and paleosoils is sharp and erosional. The sedimentological and foraminifera analyses support the identification of paleotsunamis. Based on the radiocarbon dating, it was interpreted that these three paleotsunamis occurred in the 17th, 18th, and 19th century. This first paleotsunami study in Palu, not only provided geological evidence of paleotsunamis, and extended the tsunami record in Palu, but also served as an essential start for tsunami geology study in Palu as the tsunami sources in this area are complex.

This paper presents seismic hazard and risk assessment for the state of Mizoram based on a classical probabilistic seismic hazard analysis and event-based probabilistic seismic risk analysis. For the seismic hazard estimation, analysis has been performed considering the areal source model, fault zone polygon, and smoothed gridded seismicity model. The earthquake activity rates for these source zones and smoothed gridded seismicity sources are estimated from the homogenized and declustered earthquake catalogue. The logic tree framework is applied in the seismic source models and Ground Motion Prediction equations (GMPEs) to account for the epistemic uncertainties. Five Next-generation attenuation (NGA) GMPEs for the active shallow region and three GMPEs for the Indo-Burma subduction zone have been used to evaluate the hazard at the reference rock condition (Vs30 ​= ​760 ​m/s). Peak Ground Acceleration (PGA) and Spectral Acceleration (SA) at 0.2 s and 1s are estimated for each eight districts headquarters of Mizoram for a 2% and 10% probability of exceedance in 50 years. The hazard curves and Uniform Hazard Spectra (UHS) are also presented. For seismic risk analysis, building exposure data are based on digitized building footprint and 2011 Housing Census data of India. All the buildings are classified into three classes, and seismic vulnerability functions are assigned to each building class. The area per building class is assigned from the digitized footprint. Building replacement costs per square meter have been chosen based on expert input and values identified from past study. Lastly, the study conducted a seismic risk analysis using the Open Quake-engine's probabilistic event-based methodology to estimate risk metrics at the district level, such as average annual losses and probability curves for loss exceedance. The study's findings provide valuable insights into the most high-risk areas, the building construction types that are most vulnerable to seismic activity, and the anticipated economic losses in the state of Mizoram. These results can serve as a guide for local government authorities in developing future city plans and implementing earthquake risk mitigation strategies.

After the fall of Communism in the Czech Republic, the centralised flood management was entrusted to a municipality. The new approach to disaster management in 1997 emphasised on emergency preparedness at the local level. The changing paradigms of emergency management and the changing rules and regulations of insurance companies have increased the responsibility of the local government to reduce the loss of property and save lives in villages. A qualitative method was used to explore a phenomenon in a bounded system and to understand the role and responsibilities of the municipality and the villagers' expectations. In addition, policy papers were examined to help understand the emergency planning of the municipality. The study found that successful emergency leadership is associated with adequate planning, appropriate strategies and effective implementation. The leaders must encourage subordinates and other individuals to participate actively in emergency management. It has been observed that the mayor created a ‘sense of urgency’ after assessing the prevailing institutional situation so that the plans to manage the emergency may be implemented immediately. The municipality also improves its disaster management strategies by identifying the causes of failure in the past, rectifying existing gaps, building confidence among villagers and preventing migration. It is not expected that all the stakeholders, staffs and elected members at the grassroots level engage in emergency management activities equally. However, leadership of a mayor can bind all the stakeholders to achieve a successful emergency management. They may not have adequate emergency management knowledge, but the sharing of knowledge through workshops and training programmes enhance their skills. The effective emergency management at the grassroots level not only requires collaborative strategies and human resource management, but also needs adequate management of funds. Because the local government can not always depend on voluntary participation and contribution, in which the mayor plays an important role.

The present study focuses on developing a landslide susceptibility zonation (LSZ) using GIS-based bivariate statistical model in the Lunglei district of Mizoram. Initially, 17 factors were selected after calculating the multicollinearity test for LSZ. A landslide inventory map was created based on 234 historic landslide events, which were randomly divided into training (70%) and testing (30%) datasets. Using the Index of Entropy (IOE) model, nine causative factors were identified as having significant weightage for LSZ: elevation, slope, aspect, curvature, normalized difference vegetation index, geomorphology, distance to road, distance to lineament, and distance to river. On the other hand, factors such as land use land cover, stream power index, terrain ruggedness index, terrain roughness, topographic wetness index, annual rainfall, topographic position index, and geology had negligible weightage. Based on the relative importance of the causative factors, two models were developed: scenario 1, which considered nine factors, and scenario 2, which considered all 17 factors. The results revealed that 16% and 14% of the district area were identified as very highly landslide prone in scenario 1 and scenario 2, respectively. The high susceptibility zone accounted for 26% and 25% of the area in scenario 1 and scenario 2, respectively. To assess the accuracy of the models, a receiver operating characteristic (ROC) curve and quality sum ratio method was performed using 30% of the testing landslide data and an equal number of non-landslide data points. The area under the curve (AUC) for scenario 1 and scenario 2 were 0.947 and 0.922, respectively, indicating higher efficiency for scenario 1. The quality sum ratios were 0.435 and 0.43 for scenario 1 and scenario 2, respectively. Based on these results, the LSZ mapping from scenario 1 is considered suitable for policymakers to address development and risk reduction associated with landslides.

As tourism and its related sectors have flourished in Bali Province, Denpasar Municipality, as the capital, has attracted significant urbanization. As a result of this development tendency, the city has become the densest location in the Bali Area. Denpasar Municipality is suffering with urban issues such as waste, land-use changing, housing bubble, and cultural asset loss as a result of the negative effects of urbanization. Not only from the degradation of urban livelihood threat, but Denpasar is also at risk from multi-hazard disasters such as earthquakes, tsunami, floods, extreme weather, forest and land fire, extreme waves, and beach erosion. Currently, the outbreak of the COVID-19 pandemic, as well as the decline of the tourism business, have forced Denpasar Municipality's resilience to the edge. In addition, to address the threat of disaster and urban issues in Denpasar, this research was conducted to analyze the resilience in the city. Yet, the previous studies have not been addressed the resilience of the urban crisis and disaster in a holistic approach. First, the semi-qualitative research by CDRI (Climate Disaster Resilience Index) Framework was conducted to measure the urban resilience in Denpasar. The result of five parameters (physical, social, institutional, economic, and environment) reveals that West Denpasar has the highest resilience score, followed by South, North, and East Denpasar. In addition, to assess the supporting and restricting resilience factors in Denpasar, a qualitative approach using semi-structured interviews with different responsible institutions for disaster management in Denpasar was undertaken. The result shows that sufficient infrastructure and facilities, bonus demographic, collaboration with the private sector, sufficient information access, and control from the government are the supporting factors of resilience while urbanization challenge, budget shifting, the management of the problem, the ownership of the asset, collaboration with the community and focus on physical loss and damage are the restraining factors of resilience in Denpasar Municipality.

Monitoring drought characteristics is crucial for understanding drought behaviour and developing effective mitigation plans. In this study, we analyze the characteristics of meteorological droughts in the eastern Himalayan region by utilizing both the Standardized Precipitation Index (SPI) and Copula functions. In this study, we utilized monthly rainfall data spanning 35 years to estimate three critical characteristics of droughts: duration (D), severity (S), and Intensity (I). To determine the best fit marginal distribution of each univariate drought characteristic, we employed five commonly used probability distribution functions (PDFs). We conducted Kolmogorov-Smirnov (K–S) and Anderson-Darling (A-D) tests.

The bivariate modelling for the joint D-S, S–I, and I-D datasets involves fitting Archimedean families such as Frank, Clayton, Gumbel, and Joe copulas. To perform the trivariate modelling, two meta elliptical copulas, including Normal and Frank, and two Archimedean families, namely Clayton and Gumbel, are fitted using the test statistics BIC (Bayesian Information Criterion) and AIC (Akaike Information Criterion). The cross-validation process using Maximum Likelihood Estimation (MLE) is employed to identify the most appropriate Copula model based on its goodness of fit. This step is crucial for selecting the best model to accurately describe the joint behaviour of drought characteristics. Once the best-fit Copula model is determined, it is utilized to estimate the return period of various drought characteristics, thereby facilitating the investigation of their joint return period. Furthermore, the distribution of S, D, and I classes is categorized into different return periods (T) to facilitate drought management planning.

The findings revealed moderate drought conditions were recorded for SPI 1 and SPI 3 with a 2–5 years return period. For SPI 1, this drought class remains seasonal even for higher return periods. Further, the drought class transitions from seasonal to quarter for SPI 3 and a return period of 10–50 years. Regarding SPI 6 and SPI 12, the drought class is seasonal for a return period of 2 years, but it later progresses into the quarter to long-term drought class.

Tsunami is one of the deadliest natural disasters that mankind has ever experienced. Over the centuries, tsunami is known to have caused massive destruction owing to widespread loss and damage to property and human life. This report deals with the tsunami of 28th September 2018, which hit the Island nation of Indonesia, especially the Central Sulawesi Island. Indonesia's geographical location along the pacific ring of fire makes the nation exceptionally prone to strong tsunami. The tsunami under consideration in this study was triggered by a strong earthquake of magnitude (Mw) 7.5 scale. Usually, a strike-slip earthquake never leads to tsunami, but this tsunami was quite unexpected as the fault mechanism involved was strike-slip (strike slip along the Palu-Koro fault). The local geology, geography and tectonic configuration are crucial parameters in determining the tsunami hazard in an area. This report tries to examine the causative factors and mechanism behind the occurrence of tsunami. Secondary factors like funnelling and bay effect, submarine landslips, liquefaction and landslides which could have amplified the effects of the tsunami are also presented. The study provides a conclusive account of the related foreshocks and aftershocks associated to the event. A study of the losses incurred, causalities and other losses has also been attempted by comparing a timeline of satellite imageries. A statistical study was made from the datasets obtained from various catalogues from 1500 till date and the salient results are highlighted.

Introduction

Kodagu district in India had catastrophic landslides in 2018, the rarest occurrence known to people until 2018. It has become an annual affair radiated to other districts of the Western Ghats range.

Aim

To explore landslide survivors' experiences, conventional knowledge, and responses during the emergency relief response.

Methods

In the emergency relief response phase, a qualitative study was conducted using the purposive sampling technique of landslide survivors in the Kodagu District. Ninety-nine participants were interviewed in 10 Focus Group Discussions (FGD). The FGDs were audio-recorded, transcribed verbatim and thematically analysed.

Results

In this study, 35 males and 64 females participated. All have endured horrifying experiences, and fear of life and social triggers have played an essential role in self-evacuation. The effective group work among the survivors was perceptible. The issues include improper communication of situational information, disruption of road and cellular connectivity, physical and mental health problems, direct and indirect losses, and other cross-cutting themes. Themes have been recognised as Experiencing the Darkness in Life; Disputed Communication; community-managed Immediate Disaster Response; Health Concerns of the Landslide Survivors; and Cross-Cutting Themes.

Conclusion

The study concludes that community-driven community-managed evacuation minimised the causalities. The response from the government in the immediate disaster response phase was satisfactory; fear of life and social trigger played a vital role in the self-evacuation, subsequently reducing the casualties. With community participation, disaster planning at the village/ward level would be the way forward for the well-coordinated emergency relief response.

The concept of vulnerability overarches as a multidisciplinary subject. The umbrella term is widely used in several disciplines namely sociology, public health, geography, and disaster studies. Broadly, people at risk and having potential losses are vulnerable. However, the majority of the researchers in the field consider that vulnerability is mostly socially constructed. The present paper has aimed to trace the journey of the concept of socio-economic vulnerability through an unstructured but in-depth review of the literature. The literature with the highest citations was selected from several databases such as Scopus, JSTOR and Google Scholar with the keywords such as “socio-economic vulnerability” and “social vulnerability”. A systematic selection process delivered 87 articles for review. The review reveals that the concept emerged from the political-economic view of linking people's vulnerability as a result of larger socio-political conditions and lack of people's access to resources to cope with the devastating effects of disasters and climate change. The paper identifies the pioneers in the field, the theoretical development of the concept guided by empirical findings and the methodologies which are currently used. The paper finds that there has been heavy reliance on quantitative approach and index-based method. Conceptually the discussion is dominated by political economic and structural approach. Empirical studies in India identified eastern zone as the most vulnerable area in the country. The paper suggests methodological changes for future research.

Extreme precipitation events and associated hazards are becoming more frequent and intense due to climate change. On June 2021, a devastating flash flood occurred in the Melamchi River in Nepal causing immense destruction to lives and property. The flood event was cascading in nature and associated with multiple driving factors. This study evaluates the post-extreme flood conditions of the Melamchi Flood 2021 (MF21). Rainfall, streamflow (discharge), and gauge height (water level) data of the nearest stations were analyzed. Since there was a lack of reliable instantaneous river discharge during the disastrous MF21, this study developed the flow rating curves at hydrometric stations. Post-extreme flood was evaluated considering upstream catchment hydrology, glacial lake outbursts, landslide damming, and the hydrodynamic propagations using the Hydrologic Engineering Center's River Analysis System (HEC-RAS) model and gauge-to-gauge (G2G) correlation. The results were then compared to field observations. The HEC-RAS model was simulated for several flood frequency periods in different return periods (namely 2, 5, 10, 25, 50, 100, 200, 500, and 1000 years). Results showed that the average 24 ​h gauge height and discharge at Nakote station (a few km downstream of landslide damming) are 15.88 ​m and 169.18 ​m³/s, in which the model-based highest frequency of 1-h extreme flood and return period can reach 716 ​m³/s in 1000 years. During MF21, the discharge of the Nakote region at the 10 ​min intervals was estimated to be with a maximum of 7162.10 ​m³/s, an average of 2207.13 ​m³/s and a minimum of 237.44 ​m³/s.Additionally, the outburst discharge from glacial lake at high elevation was estimated to be 295.14 ​m³/s contributing to downstream flooding. The model-based discharge during the past flood period was also estimated in 9 cross-section points of the river in which discharge at the damming area was 63.81 ​m³/s and downstream Dumredovan was 1206.58 ​m³/s. This research provides valuable insights to post-extreme flood evaluation and the approach can be used for other watersheds in evaluating post flood conditions.