Flood modelling and proposed Blue-Green Solutions – A case study in Lisbon, Portugal

Abstract. This study assesses the potential benefit of Blue-Green Solutions (BGS), green rooftops, rain gardens, permeable pavements, and bioswales, in Lisbon, Portugal. These proposed mitigation measures are applied using TFM-DYN (Nilsson et al., 2021) to simulate potential fluvial flooding distributions from a 10- and 50-year rain event.

Water depth of over 30 centimeters can cause damage to infrastructure. The model results show water depths of over 40 centimeters in some parts of the study area for the 10-year return period, raising the need for action. For the 50-year return period even more areas will be affected. These floods can occur at a relatively rapid pace. Four BGS were implemented for flood mitigation. Areas with green roofs and rain gardens showed a lowering in water depth for both return periods. This study shows that even relatively simple data allows for an estimation of urban flooding and the potential effect of BGS for specific locations can easily be determined.