UNSAFE: An UNcertain Structure And Fragility Ensemble framework for property-level flood risk estimation

Abstract

UNSAFE adopts and expands on a property-level risk assessment framework common in academic research and practice (e.g., Federal Emergency Management Agency (FEMA) loss avoidance studies (Federal Emergency Management Agency, 2024), United States Army Corps of Engineers (USACE) feasibility studies (United States Army Corps of Engineers, 2015)). UNSAFE allows users to add parametric uncertainty to building inventories, such as the widely used National Structure Inventory (NSI) dataset (United States Army Corps of Engineers, 2024c) (i.e., uncertainty in exposure), and facilitates the use of multiple, potentially conflicting, expert- based DDFs (i.e., deep uncertainty in vulnerability). In its current implementation, UNSAFE supports risk assessments for residential properties up to three stories, due to limitations in representing uncertainty in depth-damage relationships for other structures. This subset of structures represents a large proportion of structures exposed to flooding, and is a common inventory focus in research (Pollack, Benedict, et al., 2025).