Mortality associated to Hydro-Geomorphologic Disasters in the Great Lisbon area in the last 150 years Susana PEREIRA1, José Luís ZÊZERE1, Ivânia QUARESMA1 1 CEG, IGOT, Universidade de Lisboa, Lisboa, Portugal, [email protected] Abstract: In Portugal, social impacts caused by floods and landslides in the last 150 years were gathered in the DISASTER database. The mortality patterns of the hydro-geomorphological (HG) disasters were recently explored at the national scale, but the analysis was not expanded to more detailed scales. In the present work we explore the mortality caused by HG disasters in the municipalities of the Great Lisbon area. The main objectives of this work are: (i) the spatio-temporal analysis of hydro-geomorphological disasters occurred in the last 150 years on the Great Lisbon area; (ii) the analysis of the frequency and the temporal evolution of fatal floods and landslides; (iii) the analysis of the spatio-temporal distribution of fatalities; (iv) the verification of gender tendencies in mortalities; and (v) the evaluation of individual and societal risk. Individual risk is evaluated computing mortality rates for floods and landslides, which are calculated based on the annual average population and the annual average of fatalities. Societal risk is evaluated by plotting the annual frequency of flood and landslide cases that generated fatalities (F-N curves) for the Great Lisbon area and the whole country. The highest number of flood and landslide cases and related mortality occurred in the period of 1935– 1969. After this period, the number of flood and landslide fatalities decreased. The occurrence of flood fatalities has important clusters in Vila Franca de Xira, Odivelas, Oeiras and Lisbon Municipalities, generally associated with small watersheds. The Vila Franca de Xira municipality counts the highest number of fatalities generated by floods, and 84% occurred during a flash flood event in 25-26 November 1967. Fatalities caused by landslides mainly occurred in Oeiras and Lisbon municipalities. Flash floods caused the majority of fatalities associated with floods, while falls and flows were responsible for the highest number of fatalities associated with landslides. Males were found to have the highest frequency of fatalities. In the case of floods, the majority of fatalities were found both outdoors and inside of buildings in urban areas while fatalities inside buildings and inside a train were dominant in landslide cases. Keywords: Great Lisbon area; Disaster database; landslides; floods; mortality. 1. Introduction Mortality caused by natural hazards is usually difficult to assess in a systematic way due to both lack of temporal and geographic information (Borden and Cutter 2008) and unequivocal specification of the cause of death. In this context, databases on natural hazards can improve data quality for the study of mortality rates due to natural hazards in terms of temporal trends, spatial distribution, and epidemiological topics (Pereira et al. 2015). In Portugal the mortality patterns of disastrous floods and landslides occurred in the last 150 years were recently explored at the national scale by Pereira et al. (2015). This study was based on the DISASTER database (Zêzere et al. 2014) exploitation, which stores the social impacts caused by floods and landslides that generated fatalities, injuries, missing people, evacuated and homeless people referred to in Portuguese newspapers during the period of 1865–2010. Natural disasters do not affect people equally because there are inequalities in exposure to risk as well as inequalities in access to resources, capabilities, and opportunities, rendering certain groups more vulnerable to the impact of natural disasters (Neumayer and Plumper 2007). For example gender is a socioeconomic vulnerability factor that can justify differences in natural hazard fatalities due to different social roles that result in exposure to different environments (Fothergill 1996). 1 According to the literature flood fatalities usually occur as a result of people attempting to travel across floodwater inside a vehicle or on foot, or being caught in a farmland, being trapped inside buildings, crossing bridges, roads, or streams, and attempting to rescue others (Coates 1999; Jonkman et al. 2009). Fatalities caused by landslides frequently occur as a result of building destruction, vehicles or persons affected by landslides on roads or railroads, and attempts to rescue others (Fordham and Meyreles 2013). In the present work we explore the mortality caused by HG disasters in the nine municipalities of the Great Lisbon area. The Great Lisbon Area includes 21.2% of the Portuguese population and some of the most densely populated municipalities of the country (e.g. Lisbon, Sintra, Cascais, Loures). In addition, the Great Lisbon Area registered 47% of the national mortality associated with HG disasters (Pereira et al. 2015). The main objectives of this work are: (i) the spatio-temporal analysis of hydro-geomorphological disasters occurred in the last 150 years on the Great Lisbon area; (ii) the analysis of the frequency and the temporal evolution of fatal floods and landslides; (iii) the analysis of the spatio-temporal distribution of fatalities; (iv) the verification of gender tendencies in mortality; and (v) the evaluation of individual and societal risk. 2. Data and methods In Portugal, social impacts (fatalities, injuries, missing people, evacuated and homeless people) caused by floods and landslides during the period of 1865–2010 were gathered in the DISASTER database (Zêzere et al. 2014). A set of national and regional newspapers were used to collect data from which DISASTER cases and DISASTER events were identified. A DISASTER case is a unique HG occurrence, which fulfils the DISASTER database criteria (i.e., any flood or landslide that, independently of the number of affected people, caused casualties, injuries, or missing, evacuated, or homeless people), and is related to a unique geographic location and a specific period of time (i.e., the specific place and time where the harmful consequences of the flood or landslide occurred) (Zêzere et al. 2014). A DISASTER event is a set of DISASTER cases sharing the same trigger, which may have a widespread spatial extension and a certain magnitude (Zêzere et al. 2014). A content analysis of the newspapers reports of DISASTER cases was made in order to organize the information in a standardized format. Each DISASTER case includes details on the disaster characteristics and damages. The first includes data on type (flood or landslide), subtype, date of occurrence, location, and triggering factor (Zêzere et al. 2014). The second includes structural damages (damage to buildings and damages to train and road networks) and social consequences (human damage, gender of fatalities, and circumstances surrounding the fatalities). The total number of fatalities resulting from HG disasters is certainly underestimated because deaths that did not occur immediately after the disaster would not have been reported, and then it is not possible to asses these mortalities using newspapers as the single source of data. Details on the circumstances surrounding fatalities associated with floods and landslides were also obtained from newspaper reports. The circumstances surrounding fatalities were divided into the following classes: inside a building in an urban area, inside a building in a rural area, outdoors in an urban area, outdoors in a rural area, inside a vehicle and inside a train. For cases where fatalities occurred either inside buildings due to flooding, or debris accumulation of a landslide, or building collapse due to flood or landslide, or during a failed attempt to escape from inside a building, the surrounding circumstance of the fatality was classified as “inside a building.” These can be located in either urban or rural areas. If the fatality occurred outdoors, it was classified according to the type of area (urban, rural). Finally, fatalities were also reported as occurring inside a motor vehicle and inside a train. Individual risk was evaluated using mortality rates for floods and landslides, which were calculated based on years with population census in Portugal, i.e., normally every 10 years. Fortunately, the first modern population census in Portugal dates from 1864. The annual mortality rates were computed for each decade using the annual average of fatalities, which were then divided by the annual average population. The result was multiplied per 100,000 to scale it according to the size of population per unit time (Pereira et al. Mortality associated to Hydro-Geomorphologic Disasters in the Great Lisbon area in the last 150 years 2 2015). Societal risk was evaluated by plotting F-N curves representing the annual frequency of flood and landslide cases that generated fatalities. 3. Results 3.1 Spatial distribution of mortality The spatial distribution of flood and landslide DISASTER cases along the Great Lisbon Area is presented in Figure 1a. In the complete period of 1865–2010 371 DISASTER flood cases (2.5 per year on average) and 538 flood fatalities (3.7 per year on average) were registered (Table 1). Disastrous flood were mainly located in Lisbon, Loures and Odivelas municipalities. The Lisbon municipality registered the highest percentage of flood cases (35.8%, Table 1). Flood fatalities were mainly located in Vila Franca de Xira, Odivelas, Loures and Oeiras municipalities (Figure 1b). The municipality of Vila