Publications

Payandeh, AR; Justic, D; Mariotti, G; Huang, HS; Valentine, K; Walker, ND (2021). Suspended sediment dynamics in a deltaic estuary controlled by subtidal motion and offshore river plumes. ESTUARINE COASTAL AND SHELF SCIENCE, 250, 107137.

Abstract
Two series of opportunistic observations captured the seasonal variability in the suspended sediment concentration (SSC) within the main inlet of Barataria Bay, a bar-built estuary within the Mississippi Delta, as the offshore environment transitioned from a period of low river discharge and high cold front activity to a period of high river discharge and low cold front activity. During winter, the SSC dynamics in Barataria Pass was mostly driven by resuspension in response to cold front passages, with correspondingly high SSC of up to 1.84 g L-1. In addition to cold fronts, diurnal variability associated with astronomic tides was also present in the SSC time series. The mean SSC during spring (0.23 g L-1) was significantly higher than during winter (0.15 g L-1). Higher SSC during spring, in spite of the less frequent and weaker cold fronts, was due to the strong offshore influence of the Mississippi River plume. The longitudinal salinity gradients during spring showed the existence of freshwater intrusion, which was associated with the Mississippi River plume advected north-west by the Louisiana Coastal Current. Intrusion of the river plume though the inlet into Barataria Bay was also observed in time-series of MODIS satellite imagery during March 2018. A decomposition of the sediment flux time series revealed that subtidal motion associated with cold fronts was the primary mechanism of sediment transport during both winter and spring. While cold fronts enhance sediment export during winter, they also increase sediment import when associated with the higher offshore SSC during spring. We conclude that the sediment discharged at the mouth of the Mississippi River is not completely lost to the coastal zone, but instead partially supplied to deltaic estuaries through their seaward boundaries.

DOI:
10.1016/j.ecss.2020.107137

ISSN:
0272-7714