Floods are one of the most common and harmful natural disasters worldwide, especially in cities, due to the high concentration of people and goods in these areas.This research aims to provide an accessible and accurate means to model risks associated with floods in urban spaces using open data about a series of susceptibility and impact contributing factors. Hence, a methodology combining geoprocessing tools, additive weighting, dependence measures, and optimisation was designed to generate spatial information, aggregating the factors according to their weights and optimising the modelling of their relationships to flood risk, respectively. The application of the proposed approach to the city of Santander (Spain) yielded a flood risk map providing an accurate assessment of the ranking of flood zones reported by its City Council. The results suggested that flood mitigation might focus on the implementation of permeable pavements, due to their ease of integration in urban environments. K E Y W O R D S additive weighting, contributing factors, open data, optimisation, risk assessment, urban flooding

Hydrological behavior of pervious pavements during rainfall events is a complex process that is affected by many factors such as surface type, aggregates nature, layer thickness, rainfall height, rainfall intensity and the preceding dry period. In order to determine the influence of construction materials on the runoff attenuation capacity of pervious pavements sixteen laboratory models were created with four different cross sections obtained by combining two pervious surfaces and two subbase aggregate materials. Successive rainfall simulations were applied over the laboratory models measuring lag times, retained rainfalls, times to peak and peak outflows were registered for the simulated rainfalls. The results obtained were grouped depending on the materials used and statistically analysed in order to compare their stormwater retention and runoff attenuation capacities. Both surface type and sub-base aggregate characteristics were proven to influence the attenuation capacity of pervious pavements. While sub-base aggregate materials highly influence the hydrological performance during the first rainfall simulations, the permeable surface affects the hydrological behavior during the final rainfall events and the retention capacity variation over time.