Geotechnical Effects of 2018 Hurricane Florence

The Geotechnical Extreme Events Reconnaissance Association (GEER) Florence team of engineers deployed to southeastern North Carolina and northeastern South Carolina following Hurricane Florence with the GEER mission to “collect perishable postdisaster data that can be useful in advancing our understanding of extreme events,” and specifically, the effects of the extreme events on the geotechnical features of infrastructure. Florence’s impacts were significant and widespread because of the storm’s slow progression (4 days) across and massive rainfall (up to 34 in) on the study area. The team visited 23 dams, one levee system, seven bridges, eight roadway sites, two railroad impact areas, coastal sites in four counties, and one cemetery slope. This paper summarizes observations made by the team that characterize the event and the geotechnical infrastructure impacts along with lessons learned, both old and new. Event characteristics of note included rainfall, resulting flood flows, and impact location clusters. Infrastructure impact observations generally relate to the capacity of various structures to survive the flood flows, which typically overtopped most of the damaged structures. Lessons learned ranged from the obvious need for suitably sized spillways and culverts, bridge scour protection, and levee closures to smaller scale erosion characteristics of various infrastructure soils on dams with vegetation.