The Effects of a Novel Dredge Material Disposal Technique on Nitrate Removal in the Lower Atchafalaya River, Louisiana.

The navigation channel of Louisiana’s Atchafalaya River has been dredged since 1910.  Traditionally, dredged materials were placed on the riverbanks adjacent to the channel.  Beginning in 2002, the U.S. Army Corps of Engineers employed a new method of dredge material disposal in the Atchafalaya River.  The new method involves strategically placing dredged sediment up-river of a small, naturally occurring shoal to supplement its growth.  This alternative use of sediment adheres to the Engineering with Nature (EWN) concepts which aim to utilize natural processes to produce maximum benefit with the lowest economic and environmental impact.  In this study we compare biogeochemical processes from a traditional dredge material disposal island and an EWN island. Denitrification rates and soil properties from each island’s ecological community types were measured in order to investigate the nutrient removal capacities and associated ecosystem services provided.  Results examine differences between the two dredge material disposal methods in terms of N removal.  There are issues with large hypoxic zones in the northern Gulf of Mexico (NGOM), largely as a result of increased nutrient loading. The Atchafalaya River is a distributary of the Red and Mississippi Rivers and subsequently empties into the gulf.  Optimization of nitrate removal in the Atchafalaya River will lead to reduced nitrate loads, thus ameliorating hypoxia in the NGOM.