Identifying Local Hotspots of Compounded Physical and Social Impacts from Hurricane Helene-Induced Flood and Landslides

Effective post-disaster response is often constrained by limited resources, making it crucial to prioritize areas with greatest impact. Existing methods typically rely on isolated indicators, such as building damage, road disruptions, or social vulnerability. However, considering these indicators in isolation can misrepresent the full extent of disaster impacts on communities, which experience these challenges simultaneously. To address this research gap, we develop an event-specific, block group-scale post-disaster impact assessment approach and apply it to Buncombe County, North Carolina for the 2024 Hurricane Helene. Our approach combines flood and landslide building damage estimates, road-network-based critical service isolation, and pre-existing social vulnerability to build a Composite Vulnerability Index (CVI), which allows mapping hotspots where impacts from physical destruction are amplified by service disruption and pre-existing social conditions. Structural damage hotspots were predominantly low-elevation, rural block groups, while critical services isolation hotspots were concentrated in high-elevation, rural block groups. Within Buncombe County, of the block groups in the top decile of the CVI, 6% were not identified in the top decile of either individual metric, but were uniquely captured through the CVI, demonstrating its ability to uncover vulnerable communities that the isolated metrics would overlook. Our findings show that the most impacted communities are those simultaneously facing severe structural damage and critical-service isolation, with social vulnerability intensifying their burden. The CVI thus enables a holistic identification of the most burdened communities, supporting effective and targeted disaster response.