Master of Science (MS)
Oceanography and Coastal Sciences
The Bonnet Carré Spillway (BCS) is a Mississippi River diversion located on the southwestern coastline of Lake Pontchartrain in Louisiana. The discharge of potentially high amounts of Mississippi River nutrients and sediments during BCS diversion events has a noted ecological impact on the Lake Pontchartrain estuary. Projected river flooding prompted the opening of the Spillway from 10 January to 1 February 2016. MODIS satellite images were aerosol-corrected and then compared to in-situ measurements of inorganic sediment concentration (ISC) to derive a predictive algorithm for estimating ISC (in mg L^-1) in Lake Pontchartrain for satellite images in January and February. The new sediment imagery allowed for enhanced observation of sediment plume morphology, areal distribution, and directional motion trends within the Lake. The spatial area of sediment concentrations >50 mg L^-1 and >100 mg L^-1 within the Mississippi River sediment plume was calculated for 12 dates in January and February. The average Lake Pontchartrain ISC was calculated for 20 image dates. Results suggest that the sediment plume areal distribution was linked to BCS discharge rate in the early stages of the diversion event, while both wind speed and direction were potentially more impactful as the event progressed in time. The 50 mg L^-1 plume area peaked on 23 January at ~1,117 km&178;, 68% of total Lake Pontchartrain area, while the 100 mg L^-1 plume’s maximum distribution was observed on 29 January at which time its area was ~905 km&178;, 55% of the Lake’s total area. The sediment plume tended to be located along the southern coastline of Lake Pontchartrain and observed a general eastward motion, which was calculated to be ~1 km h^-1 for the first week of the event. Periods of strong winds from 19 to 24 January, 7 to 8 February, and 18 to 25 February corresponded to significant increases in plume area and mean Lake ISC for those date ranges. Similarly, reduced winds from 29 January to 5 February may explain observed decreases in plume area for that timeframe. Additionally, wind direction appeared to help determine the location of the areas of highest sediment concentration.
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Iles IV, Robert Lee, "Development and Application of a MODIS Inorganic Sediment Model during the 2016 Mississippi River Diversion in Lake Pontchartrain, Louisiana" (2017). LSU Master's Theses. 4423.
Available for download on Saturday, February 23, 2019