Gao et al. (2026) Flash-flood clustering and hotspot dynamics in the contiguous United States, 2000–2024

Identification

• Journal: Geomatics Natural Hazards and Risk
• Year: 2026
• Date: 2026-09-23
• Authors: Kunpeng Gao, Ziqian Wang, Guijun Xia
• DOI: 10.1080/19475705.2026.2736371

Research Groups

• Nanjing University of Industry Technology (lead institution)
• National Oceanic and Atmospheric Administration (NOAA)

Short Summary

This study examines national-scale patterns of flash-flood occurrence in the contiguous United States from 2000 to 2024, using a dataset of 89,468 reported events across 3,100 counties. The findings reveal significant clustering of flash-floods every year and unequal cumulative burden among counties.

Objective

• Investigate long-term spatial organisation of flash-flood occurrence at the county level in the contiguous United States.
• Examine relationships between event volume, county coverage, and global spatial autocorrelation across different temporal scales.

Study Configuration

• Spatial Scale: County-level analysis across 3,100 counties in the contiguous United States.
• Temporal Scale: 25-year period from 2000 to 2024.

Methodology and Data

• Models used: Spatial statistical methods (Global Moran's I, Local Moran's I) for spatial autocorrelation analysis.
• Data sources: NOAA Storm Events Database for flash-flood event records.

Main Results

• Significant clustering of flash-floods every year, with cumulative county-level burden highly unequal.
• Four long-term spatial backbones identified: high-burden counties (HB), burden-based FDR hotspots (FB), high-persistence counties (HP), and persistence-based FDR hotspots (FP).
• Annual hotspot dynamics reflect intermittent activation of the FB backbone and variable expansion beyond this backbone.

Contributions

• This study provides a comprehensive understanding of long-term spatial organisation of flash-flood occurrence at the county level in the contiguous United States.
• The findings support a five-level management framework for flash-flood preparedness, monitoring, and emergency-resource allocation.

Funding

• No specific funding information provided.

Citation

@article{Gao2026Flashflood,
  author = {Gao, Kunpeng and Wang, Ziqian and Xia, Guijun},
  title = {Flash-flood clustering and hotspot dynamics in the contiguous United States, 2000–2024},
  journal = {Geomatics Natural Hazards and Risk},
  year = {2026},
  doi = {10.1080/19475705.2026.2736371},
  url = {https://doi.org/10.1080/19475705.2026.2736371}
}