Flood-related hazard criteria during the human evacuation of underground spaces through stairs: a state-of-the-art review

Due to the increasing urbanisation trend and more recurrent flood events worldwide that are affecting exposed habitable areas like underground spaces. This state-of-the-art review presents a comprehensive analysis of the available literature that focuses on defining instability criteria for hazard assessment during human evacuation of underground flooded stairs. The studies are outlined in three main groups: theoretical, experimental campaigns and numerical approaches. Several methods for defining specific criteria were found, most of these criteria were described as a function of water depth (D) alone or in combination with velocity (V) highlighting the importance of these two water-related parameters for flood-related hazard evaluation. Succinctly, the most relevant findings and limitations of these studies are discussed and summarised in tables. A comparison with other flood-related hazard criteria in plain and mild-slope areas is presented. Finally, potential future investigation lines are proposed. Thus, this state-of-the-art review could offer a comprehensive overview of the topic and stimulate new exploratory studies in this research field yielding valuable insights that can be easily transmitted to stakeholders or non-experts and foster urban resilience during floods.