Neptune Pass is one of the most significant new distributaries of the Mississippi River to form in the 21st century. This pass at present diverts around 15–17% of the Mississippi River’s discharge toward the east of the Bird’s Foot Delta. This diversion reduces the river’s energy downstream and increased dredging needs in the lower Mississippi river. Moreover, this redistribution of freshwater and suspended sediment affects key water quality parameters throughout the estuary and coastal areas. To assess the impact of Neptune Pass on coastal water quality and circulation, we will use the Regional Ocean Modeling System (ROMS) within the msbCOAWST framework. Modeling begins in 2017, when the pass reached a width of 393.55 meters, and extends to 2019 and later years. As part of the MissDelta project, this work will use field data for model validation and aims to support future planning for the Bird’s Foot Delta.