Turbidity reduction for the West and Rhode Rivers

The West and Rhode Rivers (WRR), two mezohaline sub-estuaries of the Chesapeake Bay, contain a total volume of 26 million m³ of water and have a 78 km² watershed. Due to local runoff and the excess nutrients and total suspended solids (TSS) entering the WRR from the Chesapeake Bay, water quality in these sub-estuaries has steadily declined over the last forty years. Models and data analysis have shown that as much as 90% of nutrient and TSS inputs to the WRR enter via inflowing tidal water from the Chesapeake Bay; therefore, community outreach efforts are predicted to have little impact on water quality. Three alternative designs have been identified that have the potential to decrease turbidity and stimulate growth in subaquatic vegetation (SAV): addition of eastern oysters (Crassostrea virginica), soft-shell clams (Mya arenaria), and living shoreline restoration (LSR). The oysters and clams act as water filters, while LSR prevents runoff from entering the water. A 2-D Tidal Mixing Model (2DTMM) was developed to simulate the dynamic interaction between these alternatives and the nutrients and TSS entering the sub-estuary. The goal of this project is to find the design alternative, amount, and placement that would maximize the water quality in the WRR at minimum cost. The optimal placement and dollar-value configurations for each design alternative were further modeled in the Estuarine Eutrophication Model, which simulates improvements in dissolved oxygen concentrations and provides more precise water clarity calculations than the 2DTMM. An analysis of cost versus utility (water quality improvement, sustainability, and public approval) shows that the addition of approximately 20 million clams would be the most cost-effective alternative.