Agent-based simulation of pedestrians' earthquake evacuation; application to Beirut, Lebanon

Most seismic risk assessment methods focus on estimating the damages to the built environment and the consequent socioeconomic losses without fully taking into account the social aspect of risk. Yet, human behaviour is a key element in predicting the human impact of an earthquake, therefore, it is important to include it in quantitative risk assessment studies. In this study, an interdisciplinary approach simulating pedestrians' evacuation during earthquakes at the city scale is developed using an agent-based model. The model integrates the seismic hazard, the physical vulnerability as well as individuals' behaviours and mobility. The simulator is applied to the case of Beirut, Lebanon. Lebanon is at the heart of the Levant fault system that has generated several Mw>7 earthquakes, the latest being in 1759. It is one of the countries with the highest seismic risk in the Mediterranean region. This is due to the high seismic vulnerability of the buildings due to the absence of mandatory seismic regulation until 2012, the high level of urbanization, and the lack of adequate spatial planning and risk prevention policies. Beirut as the main residential, economic and institutional hub of Lebanon is densely populated. To accommodate the growing need for urban development, constructions have almost taken over all of the green areas of the city; squares and gardens are disappearing to give place to skyscrapers. However, open spaces are safe places to shelter, away from debris, and therefore play an essential role in earthquake evacuation. Despite the massive urbanization, there are a few open spaces but locked gates and other types of anthropogenic barriers often limit their access. To simulate this complex context, pedestrians' evacuation simulations are run in a highly realistic spatial environment implemented in GAMA [1]. Previous data concerning soil and buildings in Beirut [2, 3] are complemented by new geographic data extracted from high-resolution Pleiades satellite images. The seismic loading is defined as a peak ground acceleration of 0.3g, as stated in Lebanese seismic regulations. Building damages are estimated using an artificial neural network trained to predict the mean damage [4] based on the seismic loading as well as the soil and building vibrational properties [5]. Moreover, the quantity and the footprint of the generated debris around each building are also estimated and included in the model. We simulate how topography, buildings, debris, and access to open spaces, affect individuals' mobility. Two city configurations are implemented: 1. Open spaces are accessible without any barriers; 2. Access to some open spaces is blocked. The first simulation results show that while 52% of the population is able to arrive to an open space within 5 minutes after an earthquake, this number is reduced to 39% when one of the open spaces is locked. These results show that the presence of accessible open spaces in a city and their proximity to the residential buildings is a crucial factor for ensuring people's safety when an earthquake occurs

The use of passive seismological imaging in speleogenetic studies: an example from Kanaan Cave, Lebanon

Among many parameters that control the evolution of caves stands the volume of unconsolidated clay sediments generally produced by the alteration of the calcareous rocks. Here we introduce the use of a passive seismological imaging technique to investigate the clay deposits and estimate its total volume in a cave. Applied for the first time for speleogenesis studies, the HVSR (Horizontal / Vertical Spectral Ration) is a geophysical technique that can help better interpret cave geomorphology. We apply seismological spectral techniques (H/V ratio) on ambient noise vibrations to derive the clay volume, as well as its shape. This technique applied on the clay volume reveals some internal details, such as fallen blocks prior to the deposit accumulation and helps to understand deposit evacuation dynamics. The study focuses on the Kanaan Cave, located in Metn District, Lebanon, and reveals new stages related to the cave speleogenesis. This technique could be applied on ‘paragenetic’ caves where clay volume is frequently present in order to constrain the clay volume and reconstruct the buried floor shape of the cave, underneath the clay deposit

Stress from Urban Sprawl on the Fauna and Flora of the Beirut Metropolitan Area

Le Liban fait partie du point chaud de la biodiversité méditerranéenne et est bien connu pour son grand nombre d’espèces vivantes, spécialement terrestres. Son urbanisation incontrôlée représente la principale cause de la fragmentation des habitats de ces dernières. Cette recherche propose l’utilisation des SIG et de l’analyse du paysage pour appréhender le processus de fragmentation dans la Région Métropolitaine de Beyrouth (RMB) au cours des trente dernières années. Des images satellitaires de 1985 et 2016 ont été traitées dans un SIG et des indices de fragmentation ont pu être calculés grâce à Fragstat4.2. Cinq sites ont été étudiés à une échelle fine, afin d’identifier les causes de ce morcellement qui va en augmentant. Les résultats montrent une fragmentation croissante des espaces verts, une ségrégation considérable entre ces parcelles et une coupure de leur connectivité. Cette étude vise à proposer des méthodes d’atténuation efficaces pour la protection des espèces restantes.Lebanon is part of the hot spot of Mediterranean biodiversity and is well known for its large number of living species, particularly terrestrial ones. Uncontrolled urbanisation is the main cause of fragmentation of the habitats of these species. This research proposes GIS and landscape analysis as tools for understanding the process of fragmentation in the Metropolitan Area of Beyrouth over the last thirty years. Satellite images taken in 1985 and 2016 were processed by GIS and fragmentation indices were calculated using Fragstat4.2. Five sites were studied at a fine scale so as to identify the causes of this parcelling, which is on the increase. The results show increasing fragmentation of green spaces, considerable segregation between these patches and the breakdown of their connections. The aim of this study is to offer efficient mitigation methods for the protection of the remaining species

Une situation climatique extrême en Méditerranée orientale les avalanches au Liban

International audienc

A geostatistical approach for assessing population exposure to NO2 in a complex urban area (Beirut, Lebanon).

International audienceFew studies in the Middle East region estimated the spatial distribution of air pollutants for exposure studies. This paper presents a geostatistical approach to assess background NO2 spatial distribution and the associated exposed population in a Mediterranean city with a complex topography, Beirut. Such modeling gave an accurate mapping of the 2010 yearly background average value of NO2: it varies between 35 and 67 μg m−3 with a mean of 53 μg m−3. The mean SD of the estimated error was about 3 μg m−3. The results showed that the spatial distribution of NO2 follows a nested structuring, with a major structure related to topoclimatic characteristics (interaction topography/atmospheric flow at large scale) and a minor one linked to micro-environment and micro-climatic characteristics (interactions urban morphology/atmospheric flows at fine scale). The probability for the city's inhabitants to be exposed to NO2 levels exceeding 40 μg m−3 threshold limit set by the World Health Organization (WHO) showed that Beirut city has a real sanitary risk to the NO2 pollution. 93 % of the population (around 358,459 people) is 100 % sure to be exposed to a yearly average exceeding 40 μg m−3. This knowledge will be certainly useful for developing a tool for decision support in order to implement policies of reducing air pollution in Beirut, which is, given the results, very urgent

Identifying the impact of Beirut Airport's activities on local air quality - Part I: Emissions inventory of NO2 and VOCs

International audienceIn Lebanon, the steady growth of aircraft movements at Beirut-Rafic Hariri International Airport (RHIA) and its geographical characteristics, signifies the necessity to assess the impact of Beirut airport on air quality. Up till now, no study has assessed the impact of Beirut-Rafic Hariri International Airport (RHIA) on the air quality of Beirut. Hence, we produce the first emissions inventory of Beirut airport activities (2012)-including emissions from aircraft landing and takeoff (LTO) operations, ground support equipment, stationary sources, as well as airside and landside vehicles. This study, in which the first comprehensive emissions inventory in the Middle East region is conducted, provides a methodology to assess airport emissions in a country with no data. We estimated that in 2012, Beirut airport emitted 454.8 t of NO x , 50.7 t of NO 2 , 404.1 t of NO, and 24.4 t of VOCs. Results showed that aircraft emissions (Landing/Take-off cycle and auxiliary power units) dominate the airport emissions for NO x (91%), NO 2 (92%), NO (91%), and VOCs (58%). Our emissions estimates will be used in identifying the contribution of Beirut airport emissions to national emissions and in order to assess the airport's compliance with environmental legislations and to assess mitigation options

Atmospheric dispersion modelling of gaseous emissions from Beirutinternational airport activities

International audienceThe projected increase of civil aviation activity, the degradation of air quality and the location of Beirut Airport embedded in a very urbanized area, in addition to the special geography and topography surrounding the airport which plays a significant role in drawing emissions to larger distances, demanded anassessment of the spatial impact of the airport activities on the air quality of Beirut and its suburbs. This is the first study in the Middle East region that model pollutant concentrations resulting from an international airport's activities using an advanced atmospheric dispersion modelling system in a country with no data. This followed validation campaigns showing very strong correlations (r = 0.85) at validation sites as close as possible to emission sources. The modelling results showed extremely high NO2 concentrations within the airport vicinity, i.e., up to 110 µg•m-3 (which is greater than the World Health Organization annual guidelines) posing a health hazard to the workers in the ramp. The major contribution of Beirut-Rafic Hariri International Airport to the degradation of air quality was in the airport vicinity; however, it extended to Beirut and its suburbs in addition to affecting the seashore area due to emissions along the aircraft trajectory; this isan aspect rarely considered in previous studies. On the other hand, elevated volatile organic compound levels were observed near the fuel tanks and at the aerodrome center. This study provides (i) a methodology to assess pollutant concentrations resulting from airport emissions through the use 554 of an advanced dispersion model in a country with no data; and (ii) a tool for policy makers to better understand the contribution of the airport's operations to national pollutant emissions, which is vital for mitigation strategies and health impact assessments

Beyrouth face à l'aridification du climat

Beyrouth, capitale du Liban, est aujourd'hui confrontée à une nette dégradation de la qualité de son air. Dans le même temps, elle doit faire face au défi majeur de la pénurie hydrique, spécialement en fin de période estivale. Ces deux problèmes environnementaux, imputables à la fois aux caractéristiques du climat de la région, aux modalités d'aménagement de la ville et aux activités humaines, risquent à moyen terme de s'aggraver. En effet, le pays commence à subir les conséquences de l'évolution climatique qui touche le Proche et le Moyen-Orient : la désertification s'étend, la saison sèche s'allonge, le régime pluviométrique est modifié, les températures s'élèvent de manière significative. Or, jusqu'à présent, aucune politique de gestion n'a réellement été mise en œuvre pour répondre à de telles contraintes. Bien au contraire, on assiste au développement des initiatives privées qui accentuent la pression anthropique sur les ressources : l'urbanisation se densifie, verticalement aussi bien qu'horizontalement, les puits illégaux prolifèrent pour pallier la pénurie hydrique, la ville est asphyxiée par la circulation automobile... Finalement, on est en présence de signes avant-coureurs de l'aridification du climat qui, conjugués à l'absence de gestion de l'environnement, sont susceptibles de mettre en péril, notamment du point de vue hydrique, la situation jusqu'ici privilégiée du Liban au sein des milieux arides ou semi-arides

Agent-based simulation of pedestrians’ earthquake evacuation; application to Beirut, Lebanon

Most seismic risk assessment methods focus on estimating the damages to the built environment and the consequent socioeconomic losses without fully taking into account the social aspect of risk. Yet, human behaviour is a key element in predicting the human impact of an earthquake, therefore, it is important to include it in quantitative risk assessment studies. In this study, an interdisciplinary approach simulating pedestrians' evacuation during earthquakes at the city scale is developed using an agent-based model. The model integrates the seismic hazard, the physical vulnerability as well as individuals' behaviours and mobility. The simulator is applied to the case of Beirut, Lebanon. Lebanon is at the heart of the Levant fault system that has generated several Mw>7 earthquakes, the latest being in 1759. It is one of the countries with the highest seismic risk in the Mediterranean region. This is due to the high seismic vulnerability of the buildings due to the absence of mandatory seismic regulation until 2012, the high level of urbanization, and the lack of adequate spatial planning and risk prevention policies. Beirut as the main residential, economic and institutional hub of Lebanon is densely populated. To accommodate the growing need for urban development, constructions have almost taken over all of the green areas of the city; squares and gardens are disappearing to give place to skyscrapers. However, open spaces are safe places to shelter, away from debris, and therefore play an essential role in earthquake evacuation. Despite the massive urbanization, there are a few open spaces but locked gates and other types of anthropogenic barriers often limit their access. To simulate this complex context, pedestrians' evacuation simulations are run in a highly realistic spatial environment implemented in GAMA [1]. Previous data concerning soil and buildings in Beirut [2, 3] are complemented by new geographic data extracted from high-resolution Pleiades satellite images. The seismic loading is defined as a peak ground acceleration of 0.3g, as stated in Lebanese seismic regulations. Building damages are estimated using an artificial neural network trained to predict the mean damage [4] based on the seismic loading as well as the soil and building vibrational properties [5]. Moreover, the quantity and the footprint of the generated debris around each building are also estimated and included in the model. We simulate how topography, buildings, debris, and access to open spaces, affect individuals' mobility. Two city configurations are implemented: 1. Open spaces are accessible without any barriers; 2. Access to some open spaces is blocked. The first simulation results show that while 52% of the population is able to arrive to an open space within 5 minutes after an earthquake, this number is reduced to 39% when one of the open spaces is locked. These results show that the presence of accessible open spaces in a city and their proximity to the residential buildings is a crucial factor for ensuring people's safety when an earthquake occurs