Numerical Simulation of Navigation Channel Infilling Bay Center, Washington

A numerical model of circulation and sediment transport was applied to calculate the current, water level, and change in bottom elevation over time. This predictive capability allows for assessment of channel performance for existing and proposed configurations. The circulation model, called M2D, is a two-dimensional, depth-integrated, finite-difference model that calculates water level and two horizontal components of the current. Robust wetting and drying algorithms are contained within M2D and functioned well on the Willapa Bay tidal flats. Comparison of measured and calculated water level and velocity at three measurement stations distributed along the Bay Center channel showed good agreement, which is essential for accurate calculation of sediment transport. Calculated bottom-elevation change agreed well with measurements in areas where the bathymetry is well known, such as shoaling in the Bay Center Entrance Channel. In surrounding areas where bathymetric data were unavailable, calculated changes in bottom elevation were less accurate.