The largest flood loss driver of 2016 was the Louisiana flood in August 2016. With NOAA estimating $10B in economic loss, the meteorological statistics from this event were nothing short of staggering. Baton Rouge, LA registered 26.97” of rain in August, with over 20” falling in a 48 hour period; the monthly rainfall total broke the prior record of 23.73” in May 1907. Moreover, 20” in a 48 hour period registered well in excess of a 1,000 (500?) year period recurrence interval for this region. The impacts were widespread and historic, with river levels cresting at record heights, including the Amite River at Denham Springs cresting at 46.2’, over 5 feet higher than the prior record in April 1983.
I analyzed this event due to the wide ranging impacts. Based on a 5 by 5 meter resolution Digital Elevation Model (DEM) with lots of city level of details such as buildings and highways, JLT Re performed the 4-day rainfall-runoff simulations and obtained the flood footprint by using Hydrologic Engineering Center’s River Analysis System (HEC-RAS), United States Army Corps of Engineers. As it can be seen from the exhibit below, not only does the resulting map show the inundation extents (blue), but it also illustrates the spatially varied flood depth (in feet), which is a key factor to determine the flood severity, as well as the exposure and vulnerability analysis. Many locations (yellow dots) shown as being inundated during this event, such as Louisiana State University (LSU) Campus, I-10/I-12 from LA 73 (Prairieville, LA) to Siegen Lane, US 190 in Merrydale, etc, have all been verified with field photos taken by Civil Air Patrol. JLT Re also validated the result with FEMA hazard GIS layer (light red) published one month later after the event, and found out they are in very good agreement.
