CIRCULATION IN THE HUDSON ESTUARY

This paper describes the hydrodynamic characteristics of partially stratified water bodies, as typified by the Hudson River, and presents a number of methods of establishing a quantitative relationship of density-induced velocity and circulation to salinity levels, freshwater runoff, and tidal characteristics. These methods utilize known or measurable physical and hydraulic parameters to determine the density-induced circulation (DIC) and mixing characteristics of estuaries. The DIC concept plays an important role in estuarine discharges, and has been used to obtain an estimate of the flow available for dilution in estuaries. Dilution flows associated with this DIC pattern may be many times that of the upland runoff. They have been observed to be higher by factors of from 10 to 40 in several estuaries. A brief description of estuarine circulation patterns is given in the second section b of this paper. The third section c addresses itself to circulation patterns in partially stratified estuaries. These patterns are related to the net velocity distribution, which by and large is a result of dynamic interactions between the tidal current and density or salinity distributions. The presence of river upland runoff in a system in which waters of different density are brought into contact with each other and vertical mixing generated by tide-induced turbulence control these distributions. The fourth section d presents a number of analytical and empirical approaches to the development of a quantitative relationship of DIC and estuary dilution flow to dominating system parameters, particularly freshwater flow and salt concentration. The fifth section e employs these approaches to estimate DIC flows in the Hudson River under various hydrodynamic and meteorological conditions. Many of the studies summarized in this paper were conducted in recent years as part of Quirk, Lawler & Matusky Engineers’ continuing work effort on industrial discharges along the main stem of the Hudson River, under the author’s supervision. Additionally, much of the analytical investigations reported here have been conducted as part of an ongoing research program.I6 These studies are used as sources of information for this paper and are duly referenced.