Flood — Ascension, Louisiana

2016-08-13 to 2016-08-27 · near Hobart, Ascension, Louisiana

Event narrative

As water from two days of heavy rain across Ascension Parish and upstream drained into the Amite River, record levels were recorded on the river. Due to the extremely high water levels on the river, water actually flowed back upstream along streams and bayous throughout Ascension Parish leading to a significant backwater flooding problem. Flooding for this event far exceeded the 1% annual risk flood plain. In all, approximately 16,000 homes and businesses suffered varying degrees of damage, though it is somewhat difficult to determine how many were due to the initial flash flooding and how many were due to the subsequent river flooding. The end time of the flood event is approximately 24 hours after cuts were made into Aligator Bayou Road to drain water that was trapped in the area. Some lingering flooding did continue beyond this date.

Wider weather episode

A slow moving low pressure system brought widespread showers and thunderstorms to the area. The system tapped into deep tropical moisture resulting in very intense rainfall across a large portion of the area. Two-day rainfall totals of 10 inches or more were common across areas generally to the west and northwest of Lakes Pontchartrain and Maurepas. The heaviest rainfall occurred across a swath of East Baton Rouge, Livingston, and St. Helena Parishes, where 20 to 30 inches fell over a 48-hour period, topping the 0.1% annual exceedance probability. The heavy rainfall led to widespread flash flooding and record river flooding. Many of the broken records had been set during the flooding of April 1983. In total, 12 people died in southeast Louisiana as a result of the flooding. The event was also responsible for an estimated total of ten billion dollars in damage across southern Louisiana and southern Mississippi. This estimate includes impacts of both the initial flash flooding and the resultant river flooding.

View location on OpenStreetMap → (30.3420, -90.9280)

Source: NOAA Storm Events Database, event_id 657049. Narrative written by the NWS forecast office that issued the report.