I, like so many of us, am trying to wrap my head around the catastrophic damage that occurred in Western North Carolina and the Southeastern United States as a result of Hurricane Helene. The images of the flooding and damage are literally unfathomable. And what I realized is that I don’t think the United States has ever been impacted by a storm that produced precipitation of this extreme magnitude.
I am a Water Resource Engineer with expertise in hydrology and was blown away by the precipitation totals from this storm. The observed maximum precipitation depth in Busick, NC was approximately 31.2 inches of rain that fell in a 72-hour (or 3-day) period (not accounting for the precipitation that occurred leading up to the Helene event).
Pulling data from NOAA Atlas 14 https://hdsc.nws.noaa.gov/pfds/ I confirmed the 1000-year storm event for Busic, NC has a 3-day storm depth of 15 inches. This means Helene produced two times the amount of precipitation associated with a 1000-year storm. Since the relationship between precipitation depth and recurrence interval is exponential, this would be a much larger event than simply estimating it as a 2000-year storm event.
I graphed the various recurrence intervals and corresponding precipitation depths to formulate a trendline to extrapolate the recurrence interval for Helene. This rough estimate yielded a Hurricane Helene storm recurrence interval of approximately a 30,000-year storm event. This QPF area is shown as blue in the exhibit and labeled as >1000 yr. By comparison, I read an estimate that the precipitation associated with Hurricane Katrina was a 400-year storm event and Hurricane Harvey in Houston was a 2000-year storm.
Water Resource and Civil Engineers typically utilize the 100-year storm event to design roads, bridges, and structures elevated at or above this elevation. The fact that Hurricane Helene was so many orders of magnitude above this design storm, and I think any prior storm that has previously impacted the US, highlights why there is so much devastation and destruction from Helene.
Please feel free to share and pray for those suffering from this cataclysmic storm. I anticipate that once the losses are realized, this will be the deadliest natural disaster in US history as there are currently remote areas of the Appalachians that are totally cut off with no ability to escape and no access to food, water, medicine, and supplies. Find more information and please consider donating or volunteering at https://hurricanehelenewnc.com/
