Spatiotemporal Characterization of of the impact of Hurricane Michael on Urban Vegetation Cover in Panama City and Panama City Beach, Florida

Abstract

Abstract The impacts of major climatic events on urban vegetation cover are not well understood. We used Landsat 8 ETM + derived land cover in Google Earth Engine (GEE) to determine damage to urban vegetation, and Optimized Hotspot and Outlier Analyses to identify significant spatial clusters of hotspots and cold spots from Hurricane Michael in Panama City and Panama City Beach, Florida. We used two vegetation indices (Normalized Difference Water Index-NDWI and Enhanced Vegetation Index-EVI) to assess the impact of Hurricane Michael on urban vegetation cover. Results show that more than 30.07% of the land cover changed after two months of the hurricane landfall, including a rapid increase of 19.64% in water bodies. Overall, we observed a 4.91% decrease in vegetation cover, out of which 34.44% were coastal woody wetlands. NDWI showed a rapid increase due to an increase in water coverage in the study area, whereas EVI decreased due to vegetation loss by strong winds and intense precipitation. After Hurricane Michael, hotspots for high water content in sustained vegetation (NDWI) and overall vegetation condition (EVI) were discovered in Panama City Beach, Southport, and Youngstown CCD (census county division). Statistically significant (≥ 95% confidence, z ≥ 1.96) increases in NDWI hotspots (76.11% of the total area) were observed post-hurricane due to an increase in water bodies. EVI showed a decrease of about 9.21% in hotspot areas (≥ 95% confidence, z ≥ 1.96) due to defoliation caused by hurricane force winds. Our results highlight the advantages of using spatial statistical methods that could aid the development of natural hazard mitigation plans and risk reduction strategies by characterizing urban vegetation status in the Gulf Coast from previous hurricane occurrences spatiotemporally.