Impact of Urbanization on Tide and Flood Dynamics in Jamaica Bay, New York: Realistic and Analytical Modeling

Abstract:

Over the last century, estuaries and coastal lagoons have been altered by humans to facilitate navigation and development. Comparison of present-day and late 1800s elevation maps for a number of urbanized estuaries reveal significant changes in bathymetry, seafloor roughness, and surface area, which can have implications on hydrodynamics. An example of a heavily modified estuary is Jamaica Bay, New York. Recovered and digitized tidal gauge observations reveal an increase in tidal range in the bay, but the causes for such a shift remain poorly understood. To explore how human activities have altered barotropic tide and storm surge dynamics in the bay, we use a 2D numerical model with realistic bathymetry and depth-dependent bottom roughness. Model results indicate a shift from damped tide and surge reflection in the 1870s to amplification and reflection in the present-day scenario. The model also suggests that the tidal wave is progressive with a travel time of about an hour from the inlet to the head of bay in the 1870s, contrary to earlier models of lagoon hydrodynamics that assume a standing “pumping” mode response for water elevation. Although the bay has particularly complex and unnatural bathymetry and shoreline configurations, the lowest-order dynamic responses to anthropogenic change and sea level rise are reasonably captured by an analytical model that consists of prismatic channels of different depth and width with matching boundary conditions at their junctions. By studying the bay dynamics with realistic and analytical models, we find that tidal elevation has been sensitive to the extent of wetland coverage, inlet geometry, bed roughness, and bathymetry.