Flood risk assessment and mapping in peri-urban Mediterranean environments using hydrogeomorphology. Application to ephemeral streams in the Valencia region (eastern Spain)

► We introduce a qualitative approach to map flood risk in Mediterranean environments. ► Hazard is estimated by hydrogeomorphological methods and exposure from land-uses. ► We elaborate synthesis maps to spatially rank the risk according hazard and exposure. ► This differentiation is useful for planning and risk management. ► The method is easy to apply and transfer to other scenarios. This paper proposes a methodology for mapping flood risk in ephemeral streams, based on assessing flood hazards and global exposure. The method has been applied to the peri-urban area of Valencia, extended over the floodplains of the Barranco del Carraixet and Rambla de Poyo catchments. Hazard was assessed using hydrogeomorphological methods. Global exposure was estimated as a combination between the economic value of land use and human exposure, following a previous study carried out by Camarasa, A.M., López, M.J. and Soriano, J., 2011. Mapping temporally variable exposure to flooding in small Mediterranean basins using land-use indicators, Applied Geography 31 (19), 136–145. Synthesis mapping was elaborated to spatially rank flood risks, in terms of their hazard and exposure components. The method is simple, effective and easily comparable. The results reveal diverse risk configurations for each floodplain, even though both are in the vicinity of Valencia city (metropolitan area). This flood risk mapping method is very useful for land use planning because it enables swift diagnosis of the nature of risks and can supports decision making by risk managers and urban planners.