Application of a Sediment Transport Model (BFSED) to Assess the Impact from Bridge Reconstruction in the Barrington River, RI

Abstract

The study demonstrates a complete modeling system for sediment transport computations. The system contains an implementation of the BFSED model within a map-based, graphical user interface including a sophisticated, boundary -fitted hydrodynamics model (BFHYDRO), tools for collecting and manipulating input data and analyzing and animating model results. The hydrodynamic model predicts that changes in the tidal current velocity as a result of the proposed bridge causeway configuration are limited to the area near the Route 114 Bridge. Opening the existing west causeway results in a decrease in current speed across the bridge opening, but an increase in current speed over an area adjacent to the section removed from the west causeway. The area of increased current5 speed is a potential new source of sediment erosion and transport up and down the river. The results of the coupled BFSED-hydrodynamic model predict a marked decrease in the speed of maximum flood currents across the bridge opening after construction of the replacement bridge. The hydrodynamic model also predicts an increase in tidal current speed in areas adjacent to the causeway sections to be removed, potentially changing the dominant process in these areas from net deposition to net erosion and causing a predicted redistribution of the eroded sediment to other parts of the estuary. The BFSED model was used to predict the maximum depth of erosion expected to occur in the areas of increased flow, the volume of sediment eroded from these areas, and the spatial distribution of the resulting sediment deposits.