Compound Flooding in a Subtropical Estuary Caused by Hurricane Irma 2017

Hurricane Irma affected the Florida peninsula from 10 to 12 September 2017. The peninsula's east coast was hit hardest: city of Jacksonville flooded around St. Johns River estuary with storm surge that exceeded 1.5 m and rainfall surpassed 20 cm in 24 hr. This study used observations such as water wind velocities, river discharge, salinity data determine whether compounding forcings influenced flood levels. Results show flooding initiated by ocean (first punch) then exacerbated discharge (second punch). 1–2 punch caused record flooding, impacts lasting through September. Peak occurred while winds were receding, increasing, rather than at peak either process. Compound models should consider phase lag between driving processes, individual maxima may not occur simultaneously, yet still exacerbate flooding.