Seismic damage assessment based on regional synthetic ground motion dataset: a case study for Erzincan,Turkey

Estimation of seismic losses is a fundamental step in risk mitigation in urban regions. Structural damage patterns depend on the regional seismic properties and the local building vulnerability. In this study, a framework for seismic damage estimation is proposed where the local building fragilities are modeled based on a set of simulated ground motions in the region of interest. For this purpose, first, ground motion records are simulated for a set of scenario events using stochastic finite-fault methodology. Then, existing building stock is classified into specific building types represented with equivalent single-degree-of-freedom models. The response statistics of these models are evaluated through nonlinear time history analysis with the simulated ground motions. Fragility curves for the classified structural types are derived and discussed. The study area is Erzincan (Turkey), which is located on a pull-apart basin underlain by soft sediments in the conjunction of three active faults as right-lateral North Anatolian Fault, left-lateral North East Anatolian Fault, and left-lateral Ovacik Fault. Erzincan city center experienced devastating earthquakes in the past including the December 27, 1939 (Ms = 8.0) and the March 13, 1992 (Mw?=?6.6) events. The application of the proposed method is performed to estimate the spatial distribution of the damage after the 1992 event. The estimated results are compared against the corresponding observed damage levels yielding a reasonable match in between. After the validation exercise, a potential scenario event of Mw?=?7.0 is simulated in the study region. The corresponding damage distribution indicates a significant risk within the urban area.     

A GIS-based tool for flood damage assessment and delineation of a methodology for future risk assessment: case study for Annotto Bay,Jamaica

Natural Hazards - Flood risk assessments and damage estimations form integral parts of the disaster risk management in Jamaica, owing its vulnerability to hydrometeorological hazards. Although...     

Spatial and temporal variability and risk assessment of regional climate change in northern China: a case study in Shandong Province

Natural Hazards - Based on meteorological data from 20 meteorological stations in Shandong Province from 1984 to 2019, this paper analyses the spatial and temporal variability of climate elements...     

Applicability of TRMM satellite precipitation in driving hydrological model for identifying flood events: a case study in the Xiangjiang River Basin,China

The spatial and temporal distribution of forest fires displays a complex pattern which strongly influences the forest landscape and the neighbouring anthropogenic development. Statistical methods developed for spatio-temporal stochastic point processes can be employed to find a structure, detect over-densities and trends in forest fire risk and address towards prevention and forecasting measures. The present study considers the Portuguese mapped burnt areas official geodatabase resulting from interpreted satellite measurements, covering the period 1990–2013. The main goal is to detect whether space and time act independently or whether, conversely, neighbouring events are also closer in time, interacting to generate clusters. To this purpose, the following statistical methods were applied: (1) the geographically weighted summary statistics, to explore how the average burned area vary locally through the investigated region; (2) the bivariate K-function, to test the space–time interaction and the spatial attraction/independency between fires of different size; and (3) the space–time kernel density, allowing elaborating smoothed density surfaces and representing over-densities of large versus medium versus small fires and on north versus south region. The proposed approach successfully allowed finding and mapping spatio-temporal patterns within this large data series. Specifically, medium fires tend to aggregate around small fires, while large fires aggregate at a larger distance and longer times, indicating that the return time following these events is longer than for small and medium fires. The density maps shows that hot spots are present almost each year in the northern region, with a higher concentration in the northern areas, while the southern half of the country counts lower surface densities of fires, which are mainly concentrated in the central period (2000–2007).     

An ensemble risk assessment model for urban rainstorm disasters based on random forest and deep belief nets: a case study of Nanjing,China

Natural Hazards - Effective management of rainstorm risk is essential for reducing regional rainstorm disaster risks and losses. In this paper, we discussed the influencing factors of urban...     

GIS-based flood risk assessment in suburban areas: a case study of the Fangshan District,Beijing

Suburban areas have become rapid development zones during China’s current urbanization. Generally, these areas are also regional precipitation centers that are prone to flood disasters. Therefore, it is important to assess the flood risk in suburban areas. In this study, flood risk was defined as the product of hazard and vulnerability based on disaster risk theory. A risk assessment index system was established, and the analytic hierarchy process method was used to determine the index weight. The Fangshan District in Beijing, China, which is an example of a typical suburban area undergoing rapid urbanization, was selected for this study. Six factors were considered in relation to hazard, and three factors were considered for vulnerability. Each indicator was discretized, standardized, weighted, and then combined to obtain the final flood risk map in a geographical information system environment. The results showed that the high and very high risk zones in the Fangshan District were primarily concentrated on Yingfeng Street, Xingcheng Street, Xincheng Street, and Chengguanzhen Street. The comparison to an actual flood disaster suggested that the method was effective and practical. The method can quantitatively reflect the relative magnitude and spatial distribution patterns of flood risk in a region. The method can be applied easily to most suburban areas in China for land use planning and flood risk management.     

Influence of coal mining on regional karst groundwater system: a case study in West Mountain area of Taiyuan City,northern China

Karstic limestone formations in the West Mountain area are important water resources for Taiyuan City in Shanxi Province, northern China, which is also known for its large-scale coal mining production. In this study area, groundwater is not only exploited for water supply purposes but also drained because of coal mining. The process of coal mining changes both the quantity of the karst springs and the quality of karst groundwater system because of overexploitation and overdrainage. In this paper, the influence of coal mining on the groundwater is analyzed from a qualitative and quantitative perspective. The hydrochemical analysis results reflect the relationship of the recharge, runoff, and drainage; the features of the medium; and water-rock interactions. Based on a qualitative understanding of the geological deposition and characteristics of the groundwater flow system, three-dimensional groundwater flow models are established and applied to several scenarios to explore the quantitative influence and allow better protection of the groundwater environment and better utilization of water resources.     

Fire danger assessment with remote sensing: a case study in Northern China

Every year several million hectares of forest and grassland in China are affected by wildfires. The majority of wildfires occur in the northern part of China, where grasslands and forests are ubiquitous. A critical step toward the protection of life, property, and natural resources from wildfires is the development of a fire danger rating system. This paper presents a new method to assess fire danger that capitalizes on the abundance of environmental data available via remote sensing and applies this new method to the northern part of China. Using an analytical hierarchy process, a fire danger index was developed based on five environmental factors that are known to affect fire frequency and severity, including land surface temperature, vegetation curing, equivalent water thickness, vegetation continuity degree, and fuel weight. Data for these five factors were derived from satellite imagery, instead of point data, allowing for predictions to be made over a large geographic area. Fire danger ratings were then mapped for the region based on the fire danger index. In addition, the accuracy of the fire danger index was evaluated by statistical analyses. The fire danger index was significantly correlated with air temperature and precipitation, suggesting that changes in these two environmental variables will affect the predictions of the index.     

Pollen distribution in large freshwater lake of arid region: a case study on the surface sediments from Bosten Lake,Xinjiang, China

The interpretation of the pollen records from lake sediments is always hampered by a lack of information relating to different pollen production, transportation, deposition, and preservation. It is important to understand the modern process of pollen sedimentation and its climatic implications. This paper presents results from a palynological study on 61 surface sediments samples from Bosten Lake, the largest inland freshwater lake in China. Our results suggest that Chenopodiaceae and Artemisia dominate the modern pollen assemblages and have stable percentages at most sites of the lake basin except for the estuary area. Pollen Artemisia/Chenopodiaceae ratio is about 0.5, indicating the dry climate of the region. Principle Components Analysis (PCA) of pollen data can identify the pollen samples as several ecological groups from different parts of the lake. Pollen transportation dynamics and the mixing effect of lake currents and waves on pollen deposition have affected the pollen assemblages. The distribution of Typha pollen seems to be affected by the location where the parent plants grow. Picea pollen has higher percentages at estuary area, suggesting fluvial transport. Pollen concentration has high values at the central part of the lake basin due to the sedimentation focusing process effect. Our results suggest that the pollen assemblages of the sediment core from the central part of the lake can potentially record the regional vegetation history.     

Use of flood chronology for detailed environmental analysis: a case study of Lake Kizaki in the northern Japanese Alps,central Japan

This paper presents a study of the usefulness of flood layers as a time marker in sediments and a report of a case study of Lake Kizaki in central Japan. A flood layer can be identified as a layer having a higher density, coarser grain size, lower TN content, and higher C/N ratio than those of the upper and lower horizons. It can also be characterized by a hyperpycnal sequence composed of a basal coarsening-upward unit and a top fining-upward unit. When flood layers can be correlated with heavy rains in meteorological records, detailed age markers are well established in the sediment. Five flood layers were identified in the surface sediment of Lake Kizaki, and they could be attributed to the historical heavy rainfalls that took place on July 12, 1995; September 28, 1983; August 25, 1974; September 26, 1959; and September 1, 1949 under the constraint of an age model. A precise age model is essential to clarify the environmental changes such as the pollutant history in detail.     

Hazard assessment of underwater landslide-generated tsunamis: a case study in the Padang region, Indonesia

Submarine landslides can generate local tsunamis with high run-ups, posing a hazard to human lives and coastal facilities. Both ancient (giant Storegga slide off Norwegian coast, 8200 B. P.) and recent (Papua New Guinea, 1998) events show high potential danger of tsunamigenic landslides and the importance of mitigation efforts. This contribution presents newly discovered landslides 70 km off Padang (Western Sumatra, Indonesia) based on recent bathymetry measurements. This highly populated city with over 750,000 inhabitants exhibits high tsunami vulnerability due to its very low elevation. We model tsunamis that might have been induced by the detected landslide events. Estimations of run-up heights extrapolated from offshore tsunami amplitudes for Padang and other locations in the northern Mentawai fore-arc basin yield maximum values of about 3 m. We also provide a systematic parametric study of landslide-induced tsunamis, which allows us to distinguish potentially dangerous scenarios for Padang. Inside the fore-arc basin, scenarios involving volumes of 0.5–25 km³ could endanger Padang. Apart from slide volume, the hazard distribution mainly depends on three landslide parameters: distance to Padang, water depth in the generation region, and slide direction.     

Physically based dynamic run-out modelling for quantitative debris flow risk assessment: a case study in Tresenda,northern Italy

Quantitative landslide risk assessment requires information about the temporal, spatial and intensity probability of hazardous processes both regarding their initiation as well as their run-out. This is followed by an estimation of the physical consequences inflicted by the hazard, preferentially quantified in monetary values. For that purpose, deterministic hazard modelling has to be coupled with information about the value of the elements at risk and their vulnerability. Dynamic run-out models for debris flows are able to determine physical outputs (extension, depths, velocities, impact pressures) and to determine the zones where the elements at risk can suffer an impact. These results can then be applied for vulnerability and risk calculations. Debris flow risk has been assessed in the area of Tresenda in the Valtellina Valley (Lombardy Region, northern Italy). Three quantitative hazard scenarios for different return periods were prepared using available rainfall and geotechnical data. The numerical model FLO-2D was applied for the simulation of the debris flow propagation. The modelled hazard scenarios were consequently overlaid with the elements at risk, represented as building footprints. The expected physical damage to the buildings was estimated using vulnerability functions based on flow depth and impact pressure. A qualitative correlation between physical vulnerability and human losses was also proposed. To assess the uncertainties inherent in the analysis, six risk curves were obtained based on the maximum, average and minimum values and direct economic losses to the buildings were estimated, in the range of 0.25–7.7 million €, depending on the hazard scenario and vulnerability curve used.     

Comparison of GA-BP and PSO-BP neural network models with initial BP model for rainfall-induced landslides risk assessment in regional scale: a case study in Sichuan,China

Communities everywhere are being subjected to a variety of natural hazard events that can result in significant disruption to critical functions. As a result, community resilience assessment in these locations is gaining popularity as a means to help better prepare for, respond to, and recover from potentially disruptive events. The objective of this study was to identify key vulnerabilities relevant to addressing rural community resilience through conducting an initial flood impact analysis, with a specific focus on emergency response and transportation network accessibility. It included a use case involving the flooding of a rural community along the US inland waterway system. Special consideration was given to impacts experienced by at-risk populations (e.g., low economic status, youth, and elderly), given their unique vulnerabilities. An important backdrop to this work is recognition that Federal Emergency Management Agency’s Hazus, a free, publicly available tool, is commonly recommended by the agency for counties, particularly those with limited resources (i.e., rural areas), to use in developing their hazard mitigation plans. The case study results, however, demonstrate that Hazus, as currently utilized, has some serious deficiencies in that it: (1) likely underestimates the flood extent boundaries for study regions in a Level 1 analysis (which solely relies upon filling digital elevation models with precipitation), (2) may be incorrectly predicting the number and location of damaged buildings due to its reliance on out-of-date census data and the assumption that buildings are evenly distributed within a census block, and (3) is incomplete in its reporting of the accessibility of socially vulnerable populations and response capabilities of essential facilities. Therefore, if counties base their flood emergency response plans solely on Hazus results, they are likely to be underprepared for future flood events of significant magnitude. An approach in which Hazus results can be augmented with additional data and analyses is proposed to provide a more risk-informed assessment of community-level flood resilience.

     

Application of the dynamic bounds method in the safety assessment of flood defences,a case study: 17th Street flood wall,New Orleans

In this paper we provide a computational framework for evaluation of reliability and safety assessment of infrastructures. It is based on the combined application of the dynamic bounds (DB) method and a probabilistic finite element model (FEM). The DB improves the computational efficiency of the FEM when calculating time-dependent failure analyses of coastal and offshore structures, and can speed up the simulation process by several orders of magnitude.

Our approach is demonstrated here for an example problem, and shown to be the most efficient method in applications with a limited number of influential variables, which is true for geotechnical and coastal flood defence systems. It is applied to the 17th Street flood wall, a failing component of the flood defence system in New Orleans during Hurricane Katrina. The variation in soil parameters is a critical input in the reliability estimation of this structure, and the calculated probability of failure depends on these assumed values.     

Permeability control and flood risk assessment of urban underlying surface: a case study of Runcheng south area,Kunming

Natural Hazards - Because of climate change and rapid urbanization, urban impervious underlying surfaces have expanded, causing Chinese cities to become strongly affected by flood disasters....