| The Gulf Intracoastal Waterway as a Distributary of Freshwater to Coastal Louisiana Wetlands |
PRESENTATION
Christopher M. Swarzenski cswarzen@usgs.gov
US Geological Survey, Louisiana Water Science Center, Baton Rouge, LA 70816
Abstract
Since the early 1900’s, an extensive network of levees built for flood control have prevented the direct inflow of Mississippi River into most delta plain wetlands in south Louisiana. The supply of freshwater and sediment needed by these wetlands to flourish and keep pace with sea‐level rise has been reduced and, in many places, completely eliminated. Within the last 50 years, the GIWW (Gulf Intracoastal Waterway) has become the largest distributary of Mississippi River water to coastal Louisiana wetlands. The GIWW is a major east‐west trending ship channel traversing the entire Louisiana coast. Following natural hydraulic gradients, the GIWW captures water and sediment from the southward flowing Lower Atchafalaya River and Wax Lake Outlet, and distributes this river water to points 30 to 50 miles east and west of the intersections. The water in the Atchafalaya River mostly originates from the Mississippi River. The passive GIWW flow is controlled by seasonally changing differences in water surface elevations between the Atchafalaya River and adjacent watersheds and becomes predictable when stage of Lower Atchafalaya River at Morgan City is above 3 ft NAVD88. The GIWW has become the largest and frequently only source of Mississippi River water to many parts of coastal Louisiana. The ship channel functions like a freshwater diversion, but on a much larger scale in terms of volume and reach.
|
|
|