National Science Foundation and Charles Lamar Family Foundation

Tracing Amite River sediment in the wake of the August 2016 flood

17 months
With headwaters in Mississippi, the Amite River flows more than 110 miles eventually emptying into Lake Maurepas. Along the way, the Amite River flows through, and accepts water from a number of parishes, including the heavily populated and developing areas of East Baton Rouge and Livingston parishes. At the same time, Lake Maurepas is linked, through Lake Pontchartrain, with an important part of the southeast Louisiana coastal system, providing estuary habitat and storm protection for inland communities.

The Challenge

A heavy rain turned into a deluge in August 2016, ultimately resulting in more than 19 inches of precipitation falling in Baton Rouge and more than 31 inches in portions of adjacent Livingston Parish. This tremendous rainfall during such a short period of time overwhelmed the region’s drainage systems, including the Amite River, and resulted in widespread flooding throughout the lower portion of the drainage basin including the greater Baton Rouge area.

After the flood waters subsided, it was evident that the Amite River had transported large amounts of sediment down river and across the floodplain, as evidenced by piles of sand left in backyards, driveways, and parking lots. However, the sediment’s volume, character and depositional pattern is unknown and can tell us a great deal about how rivers respond to extreme events.

The Approach

With funding from a National Science Foundation Rapid Response Research grant and from the Charles Lamar Family Foundation, Institute researchers started took field measurements, supplemented by satellite data of the changes the flood wrought to the river’s channel and floodplain soon after the floodwaters receded. Researchers focused on locating and quantifying flood deposits on the floodplain, alterations to the channel’s location and shape, and examining the sediment discharged through the river’s mouths into Lake Maurepas and adjacent swamps.

Researchers collected 115 sediment cores and surface grab samples from the Amite River basin in an area stretching from Darlington, La. into Lake Maurepas. Sediment core analysis is underway and it’s expected that results from the work will be released in February 2018. Identifying how the August 2016 flood impacted the channel could provide crucial information to inform flood planning and navigation safety. In addition, the work would help show the potential role Amite River channel modifications, including gravel mining and channel realignment, played in the 2016 flood.