The Influence of the Hackensack Meadowlands on the Tidal Hydraulics of the Hackensack River

 

Robert Miskewitz, Research Engineer, Center for Environmental Systems,

Stevens Institute of Technology, Hoboken, NJ 

Email: rmiskew1@stevens-tech.edu

 

Richard I. Hires, Professor, Civil, Environmental, and Ocean Engineering

Department, Stevens Institute of Technology, Hoboken, NJ

 

Observations of the tide and tidal currents in the Hackensack River were made using bottom mounted Acoustic Doppler Current Profilers equipped with high-resolution pressure sensors. Ten-minute average water elevations and currents at 0.5-meter depth intervals over the entire water column were obtained at stations along the Hackensack River for periods ranging from 14 to 24 days. For a station with 10 m. average water depth in the approximate middle of the Meadowlands the observed currents were significantly affected by the presence of the bordering shallow marshes. For a typical tidal cycle the ebb currents at

this station exhibited large vertical shear. For peak ebb currents, the near surface currents exceeded 60 cm/s while the near bottom currents  were less than 20 cm/s. In contrast, the current speeds on flood were nearly uniform over depth with peak speeds less than 30cm/s. This asymmetry in the tidal currents is indicative of ebb dominance. Such striking asymmetries have not been observed in other parts of the Hudson-Raritan Estuary. The occurrence of ebb dominated tidal currents

has, however, been observed in other estuaries bordering tidal wetlands.

       

The time-averaged currents at this station (averaged over approximately 50 tidal cycles) show a typical estuarine pattern with  seaward flow of near surface water and landward flow at depths greater than 4 meters. The near surface current peak speed was 5 cm/s and near bottom it was 4 cm/s. The depth-averaged, time-averaged current was seaward at less than 1 cm/s. This small net transport seaward reflects the low freshwater input to the Hackensack River.

 

Preference: Oral Presentation