Urban seismic vulnerability assessment and emergency planning solutions

Over the last century, an exceptional w orld population’s grow th has continuously increased the demand for new land. This unprecedented settlement expansion (planned and/or informal) has compromised also territories on volcanoes slopes, in proximity of seismic active fault zones, in alluvial and landslides areas, making cities all around the w orld alw ays more prone to natural disasters. Urban seismic vulnerability, disaster risk reduction and emergency planning are becoming issues even more relevant. Despite the existence of several methods to assess seismic risk and urban vulnerability, few approaches focus on those global-city neighborhoods particularly vulnerable (e.g. high-density residential areas, central business districts, sites of historical and cultural heritage). Another crucial aspect, traditionally not so much considered in the urban vulnerability assessments, is the so-called fourth dimension of risk: “the time”. Indeed, in complex and dynamic environments typical of mega-cities, vulnerability changes in function of the time of the day, the day of the w eek and the season. The present w ork is an attempt to fill both these gaps, w hich are still open issues for the scientific community and for disaster management. The proposed GIS-based model includes (i) a physical vulnerability, determined by static characteristics of an urban environment, and (ii) a socio-demographic vulnerability, estimated interpreting dynamic behaviors peculiar of local population. In the assessment of the first parameter, several indicators are exerted: (i) main construction material used, (ii) building heights, (iii) condition of the buildings, (iv) presence of components hung on the building facades, (v) location of emergency facilities, (vi) quality of the mobility infrastructure system and (vii) availability of green and open areas. In the assessment of the second parameter, (i) an individual know ledge factor of the urban system has been correlated to (ii) the exposed population, subdivided into residents and different categories of city-users daily frequenting the neighborhood analyzed. Strictly related to the neighborhood land-uses, the extent of the different categories of exposed population changes over the time, therefore the exposure term assumes here a dynamic dimension. Results of the model applied to a case study (an historical district in the center of Istanbul, Turkey) are presented together w ith some consequent emergency planning solutions. An urban/district “emergency evacuation plan” has been developed to minimize human casualties during and after seismic shocks, to efficiently coordinate operation teams and to arrange emergency goods. Several shelter areas and a pedestrian evacuation route system are propounded for the case study.