Risk mapping of urban areas prone to flash floods in mountain basins using the analytic hierarchy process and geographical information systems

Global climate change has different demonstrable effects on ecosystem structures and socio-economic factors throughout the entire planet. 90 percent of last decade natural hazards around the world were attributed to water-related disasters. Forest-land use change, deforestation, unplanned urbanization, localization of marginal population groups in vulnerable areas, wild fires, high temperatures, unusual precipitations, among others are some of the variables that increase the probability of a water-related catastrophe. Comprehensive hazard assessments and appropriated environmental policies orientated towards risk management complemented with planning and designing of hydraulic infrastructures may contribute to decrease flash flooding risk a well as the magnitude of the potential damages. The aim of this study is to develop a consistent methodology to determine the vulnerability, threat and risk of mountain urban areas that are particularly vulnerable to the effects of heavy, rapid rains and represent the obtained results in a risk map. Identifying risk prone areas can be achieved by adapting geological-geotechnical charts, hydrological models, field inventories and official census data from the town of Unquillo, in the province of Cordoba, Argentina. The analytic hierarchy process was used in order to determine the individual contribution of each vulnerability factor, together with geographical information systems used to combine the obtained information trough algebra and transformation of satellite imagery bands. The case of study show that 59% of the total flooding vulnerability relates to the buildings infrastructure, followed by the social factors which represent 33% of the total vulnerability equation. The threat map was validated using landmarks and remains obtained as a consequence of the flooding that occurred on February 15th 2015 in the study area.