Title page for ETD etd-06162005-082538


Type of Document Dissertation
Author McGraw, Molly J.
URN etd-06162005-082538
Title The Effect of Environmental Forcing on the Suspended Sediment within the Naomi Wetlands as Reflected in Turbidity Data
Degree Doctor of Philosophy (Ph.D.)
Department Geography & Anthropology
Advisory Committee
Advisor Name Title
Richard H. Kesel Committee Chair
Dewitt Braud Committee Member
Harry Roberts Committee Member
Robert Rohli Committee Member
Steven Namikas Committee Member
Vijay Singh Dean's Representative
Keywords
  • suspended sediment
  • turbidity
  • wetlands
  • Louisiana
Date of Defense 2004-11-10
Availability unrestricted
Abstract
In recent years, several freshwater diversion structures have been constructed along the lower Mississippi River south of Baton Rouge, Louisiana. These structures divert freshwater and sediment into Louisiana’s coastal wetlands in an effort to combat Louisiana’s estimated annual wetland loss of 65 km2. The successful operation of these diversions depends upon the stage of the Mississippi River. An increase in river stage generally results in an increase in the suspended sediment load and in the discharge of water through a diversion. The subsequent transport of suspended sediment within an estuary is also influenced by local rainfall, tide, and wind speed and direction. This study examines the relationship between the suspended sediment concentration in the east-central Barataria Basin and the operation of the Naomi Siphon, Mississippi River stage, local rainfall, tide, wind speed, and wind direction.

The Naomi Freshwater Diversion, located southeast of New Orleans, diverts freshwater and suspended sediment into the Barataria Estuary. A 10-year record of monthly turbidity readings (used as a surrogate for suspended sediment concentration) from within the estuary was combined with river stage, rainfall, tide, wind speed, and wind direction data to examine the effect of these forcing factors on the turbidity and concentration of suspended sediment within the estuary.

Results indicate that suspended sediment concentrations are greatest in the areas closest to the siphon when the siphon is discharging and during periods of high river stage. Spoil banks appear to block the flow of sediment-laden sheet flow to the outer regions of the wetland. Sheet flow is diverted into canals and flows off site. Individually, tide affects only the interior wetlands, due to an increase of readily available sediment in this area. Rainfall and wind individually provide a negligible influence on suspended sediment concentrations.

Regression models of the relationship between suspended sediment concentration and the environmental forcing factors were developed. The study also determined that canals are more efficient than bayous for transporting suspended sediment. The canals appear to be funneling suspended sediment out of the wetlands.

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