High Hazard Areas Research Articles

Multi-geospatial flood hazard modelling for a large and complex river basin with data sparsity: a case study of the Lam River Basin, Vietnam

Mapping flood hazard becomes a basic and crucial requirement to cope with and to mitigate flood risks. However, it is a big challenge to accurately construct a flood hazard map in the large and sparsity data basin. Here, we present a new approach to make a flood hazard map in a large and complex river basin with data sparsity based on a comprehensive analysis of the relationship between previous flood records and hydrometeorological and geographical features coupled with holistic knowledge. The results show that the AHP-GIS approach (an integrated GIS-based Analytic Hierarchy Process method) can produce more accurate and reliable flood hazard map in basins with complex geological and hydrometeorological features such as the Lam River Basin (LRB). The LRB was a high vulnerability to flooding with approximately more than 90% of the total area in this river basin was classified into moderate, high, and very high hazard of flooding. More specifically, high, and very high flood hazard area occupied nearly 30% of the total area and affected nearly 45% of households living in the basin. More noticeable, these high flood hazard areas were in small valleys along the rivers and streams running from high mountains in the southwest to the coastal region. Moreover, the study indicated that rainfall and slope were the main factors that influence mapping flood hazard and assessing flood risk in the steep slope areas.

Creating a quantitative, ecosystem-service-based index of nature in the highly urbanized and arid Los Angeles County

Before evaluating the abundance and quality of nature in a city, one must define the concept of nature according to resident experience and climatological conditions. For Los Angeles (L.A.) County, home to a sociologically diverse and highly developed city in a Mediterranean climate that experienced drought conditions for the last decade, this represents a formidable theoretical and empirical challenge. In support of an Integrated Vulnerability Assessment, we developed an index of natural resources with the aid of local partnerships. This effort required local expert participation and resulted in the creation of a large database of available regional data. This index was created to investigate the spatial footprint of natural resources in relation to predicted high risk natural hazard areas. This paper demonstrates analytical applications of this index, which consists of six component indicators: greenness, biodiversity, habitat fragmentation, significant ecological areas, tree canopy cover, and wetland cover. Data for each component were compiled into a geodatabase, scaled, aggregated to Census block group areas, and combined to create the natural resources index (the Index). The Index can then be compared with natural hazard spatial data to determine relative vulnerability to these hazards, interactions with other types of vulnerabilities, and where adaptive capacity may be lacking. Results highlight areas of opportunity for multifaceted risk mitigation and adaptation efforts.

Pemetaan Bahaya Longsor Dengan Metode Analitycal Hierarchy Process di Arjuno Welirang, Jawa Timur

Indonesia has enormous geothermal potential because most of Indonesia's territory is located in an active volcano route. One of the challenges in developing geothermal energy is that its location is located on the slopes of a Quaternary Volcanoes which is suceptible to landslides. The purpose of the research that has been carried out is to determine the distribution of landslide-hazard areas on the western slopes of the Arjuno-Welerang Volcano. The analysis was performed using the Analytical Hierarchy Process method based on morphological, geological and structural geological parameters. Geomorphological mapping was carried out by contour map analysis, then classified based on morphometry and morphogenesis. Geological mapping uses the principle of volcanostratigraphy, while mapping of geological structures is done by analyzing contour maps made by Digital Evalation Model and field checking. The high and very high landslide hazard zones are scattered along the fault zone, while the very high landslide hazard areas are located in the ancient crater valleys.

Distribution of Groundwater Arsenic in Uruguay Using Hybrid Machine Learning and Expert System Approaches

Groundwater arsenic in Uruguay is an important environmental hazard, hence, predicting its distribution is important to inform stakeholders. Furthermore, occurrences in Uruguay are known to variably show dependence on depth and geology, arguably reflecting different processes controlling groundwater arsenic concentrations. Here, we present the distribution of groundwater arsenic in Uruguay modelled by a variety of machine learning, basic expert systems, and hybrid approaches. A pure random forest approach, using 26 potential predictor variables, gave rise to a groundwater arsenic distribution model with a very high degree of accuracy (AUC = 0.92), which is consistent with known high groundwater arsenic hazard areas. These areas are mainly in southwest Uruguay, including the Paysandú, Río Negro, Soriano, Colonia, Flores, San José, Florida, Montevideo, and Canelones departments, where the Mercedes, Cuaternario Oeste, Raigón, and Cretácico main aquifers occur. A hybrid approach separating the country into sedimentary and crystalline aquifer domains resulted in slight material improvement in a high arsenic hazard distribution. However, a further hybrid approach separately modelling shallow (<50 m) and deep aquifers (>50 m) resulted in the identification of more high hazard areas in Flores, Durazno, and the northwest corner of Florida departments in shallow aquifers than the pure model. Both hybrid models considering depth (AUC = 0.95) and geology (AUC = 0.97) produced improved accuracy. Hybrid machine learning models with expert selection of important environmental parameters may sometimes be a better choice than pure machine learning models, particularly where there are incomplete datasets, but perhaps, counterintuitively, this is not always the case.

Sentinel‐1 remote sensing data and Hydrologic Engineering Centres River Analysis System two‐dimensional integration for flash flood detection and modelling in New Cairo City, Egypt

AbstractDigital surface models, land use and rainfall data were used to simulate water areas using Hydrologic Engineering Centres River Analysis System (HEC‐RAS) software. Multi‐temporal synthetic aperture radar (SAR) was used for the detection of flood prone area to calibrate HEC‐RAS, due to the lack of data validation in the New Cairo City, Egypt. The thresholding water detection method was applied to two Sentinel‐1 images, one pre‐ and one post‐flash flood event from April 24 to 27, 2018. The threshold method was used to detect water areas from SAR Sentinel‐1 images. Feature statistical agreement F1 and F2 values ranged from 73.4 to 77.7% between water areas extracted based on backscattering values between 19.97 and 16.53 in decibels (dB) and reference water areas obtained using an optical image of the Sentinel‐2 satellite. The similarity between simulated HEC‐RAS two‐dimensional (2D) of water areas and reference water areas based on SAR data ranged between 74.2 and 89.7% using feature statistical agreement values F1 and F2. It provides a clear suggestion that, in the absence of field observations, SAR data can be used to calibrate the model. Two flood hazard maps created based on water velocity and depth were obtained from HEC‐RAS 2D simulation. The obtained maps indicated that 11% of the roads and 50% of the buildings in New Cairo City are exposed to high hazard areas. Furthermore, 28% of the bare land is situated in a very high vulnerability area. We recommend the use of obtained hazard map in supporting emergency response, and designing effective emergency plans.

Out-of-plane mechanism in the seismic risk of masonry façades

A framework for evaluating the risk of the out-of-plane mechanism of masonry facades subjected to earthquake excitations is presented. The effect of seismic events on masonry facades is investigated and results are presented in terms of fragility curves and seismic risk for several masonry supporting restrictions. The restrictions considered are (1) masonry facade unrestricted to rock on a firm base, (2) masonry facade restricted to rock in one direction, and (3) restrained rocking masonry facade in one-sided motion. Because the available empirical information is insufficient to obtain fragility functions for masonry facades, the study is based on numerical analysis and recent studies on seismic risk. The conceptual framework is illustrated with information from masonry facades characteristic of Mexican religious structures and within the seismic hazard areas of Mexico. Since the frequency characteristics of ground motions strongly depend on the distance from the epicenter to the site, which is of cardinal importance to the vulnerability of these structures, the impact of this distance for hard-soil sites is thoroughly investigated. The probability of failure for the three types of masonry facades was calculated. It was found that the probability of failure decreases with an increased width-to-height relation; conversely, the probability of failure (reported in terms of the reliability index) increases with increased block size dimensions. Results in this study show that restraining conditions of the facades inconsequentially affect the probability of failure. Although the reliability of freestanding masonry facades are marginally greater, this finding holds true regardless of whether or not one considers far-field ground motions. The results in this study can be useful for evaluation and reinforcement tasks of masonry facades located in areas of high seismic hazard.

Flood susceptibility mapping using a geomorphometric approach in South Australian basins

Watershed characteristics and their hydrological responses can have severe effects on the occurrence and extent of floods. Therefore, this study focuses on the integration of geospatial techniques and remote sensing data to identify watershed terrain characteristics and evaluate the influence of these characteristics on flood susceptibility in South Australia. Data from the Shuttle Radar Topography Mission (SRTM) and geologic and topographic maps and a geographic information system (GIS) were used to delineate drainage basins, measure morphometric parameters and link different parameters to evaluate the degree of flood vulnerability. Depending on their relations to the flood hazards, the morphometric parameters were categorized into two groups; then, a rank score was assigned to each group. Finally, the flood susceptibility of the basins was visualized, and the basins were classified into low, intermediate and high flood hazard areas. The results show that approximately 45.7, 44.7 and 9.7% of the study area is at risk of high, medium and low degrees of flooding, respectively. The results were validated through secondary data relating to historic floods. The causes of flooding were analysed using rainfall and road density data, while the consequences of flooding were verified by the population distribution across the study area. The findings of this study can be used to support decision-makers in planning and investing in mitigation measures, especially in highly susceptible areas of South Australian basins.

Zonasi kawasan perkotaan berbasis mitigasi bencana banjir (Studi kasus Kota Denpasar)

Urban zoning based of flood disaster mitigation (case study in Denpasar City). Denpasar City has been experienced a calamitous event such as flooding or inundating caused by development activities and topographical conditions of urban areas which prone to risk to flood disasters. Therefore, urban planning inDenpasar City needs to be handled by developing the concept of flood mitigation approach by considering the level of risk and the characteristics of the city of Denpasar. The purpose of this research was to developzoning concept in urban areas based on flood mitigation approach. The method used in this study wasoverlaying analysis and descriptive analysis. The results showed that the level of flood vulnerability in Denpasar city was increased from 59.62% in 2015 and reached to 61.24% in 2016. The trends caused by a high rainfall during 2016 and was influenced by the hydrogeological characteristics, slope and land use change. Based on spatial analysis, the concept of flooding mitigation formed as follows: 1) high hazard zone(refers to the concept of disaster mitigation in a high hazard area); 2) Medium hazard zone (referring to the concept of disaster mitigation in medium hazard area); 3) Low hazard zone (referring to the concept ofdisaster mitigation in low hazard area). In conclusion it recommended that the government and thecommunity need to work together while maintaining the environment and monitoring the use of space in the urban area. Further research is needed related to hydraulic conditions so that results are more valid.

Groundwater vulnerability mapping using the Susceptibility Index (SI) method: Case study of Takelsa aquifer, Northeastern Tunisia

The Takelsa phreatic aquifer currently shows stress signs and the contamination risk of groundwater by different chemical elements and pesticides is a likely concern. Here we assessed the aquifer vulnerability using the Susceptibility Index (SI) method, considered as a specific vulnerability method that takes into consideration the impact of land uses chemical fertilizers, anthropogenic activities and natural factors as a source of contaminants in groundwater. WetSpass and MODFLOW models were applied to quantify groundwater recharge and water table depth, the two of the most important parameters in groundwater vulnerability mapping.The obtained recharge map for 2015 showed values ranging between 0 and 342 mm/year with an average value of 111 mm/yr, corresponding to about 16% of the annual average rainfall. Regarding the groundwater flow model and for a steady and transient state, a reasonable correlation between the observed and simulated values was obtained confirming that results can be used to establish the vulnerability map.The Susceptibility Index (SI) results showed that the groundwater vulnerability of the studied aquifer ranges from low to very high. Most of the area (90%) has moderate to very high pollution susceptibility mainly due to low slope, agricultural land, high recharge rate, sandy soil dominance and low water table depth. The validation of the obtained map was undertaken through a comparison of areas of high salinity hazard with their relative vulnerability index. For most wells, the different salinity hazard parameters matched with areas of moderate to high vulnerability.The integration between the SI method and WetSpass and MODFLOW models for the study area is a valuable and applicable approach for the assessment of the groundwater vulnerability.

A Hybrid Approach Using GIS-Based Fuzzy AHP–TOPSIS Assessing Flood Hazards along the South-Central Coast of Vietnam

Flood hazards affect the local economy and the livelihood of residents along the South-Central Coast of Vietnam. Understanding the factors influencing floods’ occurrence potentially contributes to establish mitigation responses to the hazards. This paper deals with an empirical study on applying a combination of the fuzzy analytic hierarchy process (AHP), the fuzzy technique for order of preference by similarity to ideal solution (TOPSIS), and a geographic information system (GIS) to assess flood hazards along the South-Central Coast of Vietnam. Data are collected from focus group discussions (FGDs) with five communal authorities; a questionnaire completed by eight hamlet heads in the Phuoc Thang commune (Binh Dinh province); and documents, reports, and thematic maps provided from official sources. A total of 12 maps of flood factors are prepared. The results show that terrain elevation, creek-bottom terrains, high tide-induced flooding area, and distance to water body are the main factors affecting flood hazards. The An Loi hamlet faces the highest risk for floods, followed by Lac Dien, Luong Binh, and Pho Dong. The map of flood hazards indicates the western part is assessed as low hazard, whereas the eastern part is a very high hazard area. The study findings show that the hybrid approach using GIS-based fuzzy AHP–TOPSIS allows connecting decision makers with the influencing factors of flooding. To mitigate floods, both the Vietnam national government and the Binh Dinh provincial government should integrate natural hazard mitigation into socio-economic development policies.

Refuerzo de un edificio mediante la incorporación de un sistema de disipación de energía

En zonas de alta peligrosidad sísmica existen estructuras que pueden requerir un refuerzo estructural para mejorar su desempeño. Una alternativa para realizar estos refuerzos es la incorporación de sistemas pasivos de energía. Este trabajo tiene por objeto aplicar una metodología de diseño propuesta por el autor a un caso de estudio. Se diseñan los dispositivos y posteriormente se contrasta el método propuesto con análisis dinámico no lineal según requerimientos de la norma americana ASCE/SEI 7-16. Para la excitación sísmica se eligen dos grupos de siete registros representativos de la zona de emplazamiento escalados por ajuste espectral. En base a la consideración de varios parámetros de respuesta se muestra la eficiencia del procedimiento de diseño propuesto.

COST Action 620 Approach: Application to a Karst Aquifer, SE Mexico

AbstractThe EU Cooperation in Science and Technology (COST) Action 620 Group approach is applied to evaluate the risk of groundwater contamination of a karstic aquifer located southeast of Mexico, to get information of potentially threatened areas. Subsurface contaminant loads, the aquifer vulnerability, as well as, the interaction between them are considered to define the aquifer risk to contamination. The hazard and risk indexes are calculated from an inventory of contaminant sources, creating their maps using geographic information system. Under the COST 620 approach, any method can be used to analyze aquifer vulnerability to contamination and new ones can be developed. This allows to model the karst groundwater vulnerability to contamination in the study area, applying a modified version of the DRASTIC method, where considerations are given to hydraulic conductivity and land use, as parameters in the model. The results indicate a more conservative differentiation when compared to similar studies carried out in the study area with the moderate vulnerability class occupying the greatest extent. Areas of high hazard and risk are in the main urban areas.

Spatial risk analysis for the introduction and circulation of six arboviruses in the Netherlands

BackgroundArboviruses are a growing public health concern in Europe, with both endemic and exotic arboviruses expected to spread further into novel areas in the next decades. Predicting where future outbreaks will occur is a major challenge, particularly for regions where these arboviruses are not endemic. Spatial modelling of ecological risk factors for arbovirus circulation can help identify areas of potential emergence. Moreover, combining hazard maps of different arboviruses may facilitate a cost-efficient, targeted multiplex-surveillance strategy in areas where virus transmission is most likely. Here, we developed predictive hazard maps for the introduction and/or establishment of six arboviruses that were previously prioritized for the Netherlands: West Nile virus, Japanese encephalitis virus, Rift Valley fever virus, tick-borne encephalitis virus, louping-ill virus and Crimean-Congo haemorrhagic fever virus.MethodsOur spatial model included ecological risk factors that were identified as relevant for these arboviruses by an earlier systematic review, including abiotic conditions, vector abundance, and host availability. We used geographic information system (GIS)-based tools and geostatistical analyses to model spatially continuous datasets on these risk factors to identify regions in the Netherlands with suitable ecological conditions for arbovirus introduction and establishment.ResultsThe resulting hazard maps show that there is spatial clustering of areas with either a relatively low or relatively high environmental suitability for arbovirus circulation. Moreover, there was some overlap in high-hazard areas for virus introduction and/or establishment, particularly in the southern part of the country.ConclusionsThe similarities in environmental suitability for some of the arboviruses provide opportunities for targeted sampling of vectors and/or sentinel hosts in these potential hotspots of emergence, thereby increasing the efficient use of limited resources for surveillance.

Assessment of Agricultural Drought Risk in the Lancang-Mekong Region, South East Asia.

Natural disasters worldwide regularly impact on human activities. As a frequently occurring natural disaster, drought has adverse impacts on agricultural production. The Lancang-Mekong River is a transnational river running through China and five Southeast Asian countries and it is a vital water resource for irrigation in the region. Drought in the Lancang-Mekong Region (LMR) has occurred frequently in recent years. Assessing the risk of drought in the region is essential for rational planning of agricultural production and formulation of drought relief measures. In this study, an assessment of drought risk has been achieved by combining the hazard and vulnerability assessments for drought. The assessment of the drought hazard depends mainly on the standardized precipitation index (SPI). The assessment of drought vulnerability takes into account various indicators such as climatic factors (e.g., crop water stress index), soil factors (e.g., available water capacity), and irrigation factors (e.g., irrigation support). The results reveal that: (1) Drought distribution in the LMR is characterized by a spreading of the drought to countries along the middle and lower reaches of the Mekong River. Countries located in the middle and lower reaches of the Mekong River are more prone to drought. Laos, Thailand, and Cambodia are the regions with higher and high-drought risk levels. (2) The spatial distributions for the drought hazard and the drought vulnerability in the LMR exhibit significant differences as evidenced in the mapping results. High-hazard and high-vulnerability areas are mainly distributed in the middle LMR, and the middle to higher hazard areas and the middle to higher vulnerability areas are mainly distributed in the south-central LMR, while the low-hazard areas and the low-vulnerability areas are mainly in the north. (3) The majority of planting areas for sugarcane, rice, and cassava are located in the high-hazard areas. The distributions of drought-prone and high-hazard areas also correspond to the main agricultural areas in the LMR.

Cumulative absolute velocity (CAV) seismic hazard assessment for Taiwan

ABSTRACT Cumulative absolute velocity (CAV) is a ground motion intensity measure that is considered more indicative of structure damage than other intensity measures (e.g., PGA). Nevertheless, most seismic hazard assessments are PGA-based rather than CAV-based. In this paper, the first CAV seismic hazard assessment for Taiwan was presented. According to this CAV seismic hazard assessment, central-western and central-eastern Taiwan is of higher CAV seismic hazards than other areas. At the 475-year return period, the CAV of exceedance in those high seismic hazard areas is around 0.6–0.7 g-sec.

Does removal of federal subsidies discourage urban development? An evaluation of the US Coastal Barrier Resources Act.

Urban development relies on many factors to remain viable, including infrastructure, services, and government provisions and subsidies. However, in situations involving federal or state level policy, development responds not just to one regulatory signal, but also to multiple signals from overlapping and competing jurisdictions. The 1982 U.S. Coastal Barrier Resources Act (CoBRA) offers an opportunity to study when and how development restrictions and economic disincentives protect natural resources by stopping or slowing urban development in management regimes with distributed authority and responsibility. CoBRA prohibits federal financial assistance for infrastructure, post-storm disaster relief, and flood insurance in designated sections (CoBRA units) of coastal barriers. How has CoBRA’s removal of these subsidies affected rates and types of urban development? Using building footprint and real estate data (n = 1,385,552 parcels), we compare density of built structures, land use types, residential house size, and land values within and outside of CoBRA units in eight Southeast and Gulf Coast states. We show that CoBRA is associated with reduced development rates in designated coastal barriers. We also demonstrate how local responses may counteract withdrawal of federal subsidies. As attention increases towards improving urban resilience in high hazard areas, this work contributes to understanding how limitations on infrastructure and insurance subsidies can affect outcomes where overlapping jurisdictions have competing goals.

Social Vulnerability to Natural Hazards in Namibia: A District-Based Analysis

Southern Africa is one of the world’s poorest and most vulnerable regions with severe barriers to its sustainable development. We strived to understand here the patterns and drivers of social vulnerability to natural hazards in Namibia, which is the most arid sub-Saharan country with large social inequalities. We used a total of 12 indicators that characterized social, economic and demographic settings of the 14 districts in the country. Further, we evaluated the countrywide pattern of most relevant natural hazards, including wildfires, floods and drought. We identified the main factors driving social vulnerability in the districts, and we evaluated how the socio-economic fitness of populations coincided with the distribution of high-hazard areas. We found that populations with the poorest socio-economic performance were mostly distributed in the country’s northern districts, which are also exposed to the highest frequency and severity of natural hazards, particularly to floods and wildfires. This coincidence of highly sensitive populations with high exposure to hazards renders these populations particularly vulnerable. That the frequency of natural hazards increases with climate change, and implementation of programs enhancing the social resilience is insufficient, underscores the urgency of actions targeted at the priority areas identified herein.

WITHDRAWN: Potentially contaminated sites in China: Spatiotemporal distribution and current risk assessment

Abstract As the Chinese government stated in the Action Plan on Prevention and Control of Soil Pollution, 95% of the contaminated sites in China would be safe for use by 2030. To achieve this ambitious goal, managing potentially contaminated sites (PCS) is the first step. However, China still lacks basic information on the quantity, location, and spatiotemporal distribution of PCS, and the current risk assessment of PCS is particularly rare. In this study, we integrated China’s site survey data on PCS to analyze their spatiotemporal distribution and to assess the health risks posed by PCS. The results showed that the number of PCS in China increased from 7586 in 2000 to 38,020 in 2018, more than a fourfold increase. In 2000, very small areas had either a medium or medium-high density of PCS; however, in 2018, this density in many areas became medium-high or high, especially in Eastern China. The spatiotemporal distribution of PCS was driven by both industrialization and urbanization in China. From 2000 to 2018, the impact of these two factors on the PCS distribution in Central and Western China was generally lower than that in Eastern China. Hazard assessment indicated that relative high-hazard areas were mainly located in Shanxi, Hebei, Xinjiang, and Yunnan provinces. All provinces contained absolute high-hazard areas, except Tibet and Hunan. We present a strategy to promote PCS management based on a revised source-pathway-receptor model and to achieve the ambition on soil pollution control in China.

Identifying Forest Fire Driving Factors and Related Impacts in China Using Random Forest Algorithm

Reasonable forest fire management measures can effectively reduce the losses caused by forest fires and forest fire driving factors and their impacts are important aspects that should be considered in forest fire management. We used the random forest model and MODIS Global Fire Atlas dataset (2010~2016) to analyse the impacts of climate, topographic, vegetation and socioeconomic variables on forest fire occurrence in six geographical regions in China. The results show clear regional differences in the forest fire driving factors and their impacts in China. Climate variables are the forest fire driving factors in all regions of China, vegetation variable is the forest fire driving factor in all other regions except the Northwest region and topographic variables and socioeconomic variables are only the driving factors of forest fires in a few regions (Northwest and Southwest regions). The model predictive capability is good: the AUC values are between 0.830 and 0.975, and the prediction accuracy is between 70.0% and 91.4%. High fire hazard areas are concentrated in the Northeast region, Southwest region and East China region. This research will aid in providing a national-scale understanding of forest fire driving factors and fire hazard distribution in China and help policymakers to design fire management strategies to reduce potential fire hazards.

Spatial planning of fire-agency stations as a function of wildfire likelihood in Thasos, Greece

Even though wildfires constitute a natural phenomenon, they may have severe implications with respect to the socioeconomic structure of the affected population and the ecological wealth of a territory, especially when they burn under high intensities. Timing of the initial attack is thus crucial to fire control in areas that fires are considered to be under high threat of burning. The aim of this paper is to investigate the combined use of simulation modeling and spatial optimization to assess the pre-positioning of fire-management resources on a small Greek island, Thasos, based on the current and desired fire agency capabilities, maximization of environmental protection, and rationalization of financial resources. The estimation of burn probability (BP) depicted specific areas of high fire hazard in the southern, central, and western part of the island, where essential preventive measures should be undertaken. Based on this result, BP was then used as a primary input for the assessment of optimal locations of fire operation agencies in order to achieve the maximal coverage under certain (already available) and minimum number of fire-fighting vehicles in different time windows. The results generated three differentiated optimal location schemes [8 available vehicles within either 10 (immediate response time) or 31 min (average response time) with the current fire resources; 19 and 2 required vehicles within 10 and 31 min, respectively, based on a minimum number of fire resources]. This type of information enables us to propose a relocation of the current fire agency in a southern town of the island. The flexibility and interaction of the models provide a framework for appropriate decision making under a set of political and financial constraints.