Newark Bay Study - Passaic River Public Digital Library
Newark Bay Study - Passaic River Public Digital Library
Newark Bay Study - Passaic River Public Digital Library
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
1-51<br />
sediment transport, there is considerable information available on the rates in <strong>Newark</strong> <strong>Bay</strong>, and it is<br />
clear from this information that sediment accumulation is a dynamic process. Rates range from<br />
tenths of a cm/year in the side <strong>Bay</strong> areas to 10 – 15 cm/year or more in the primary depositional<br />
zones. This range in rates has important implications for modeling purposes, especially when it is<br />
time to perform projections. The reason is that it is the combination of the depth of the mixed layer<br />
and the net sedimentation rate that will control the response time of the system to future changes in<br />
sediment characteristics and inputs to the system. Surface sediment concentrations can be expected<br />
to respond relatively rapidly in areas having high net sedimentation rates.<br />
Suszkowski (1978) identified three areas in the <strong>Newark</strong> <strong>Bay</strong> where enhanced sediment<br />
accumulation was occurring. These areas are the lower <strong>Passaic</strong> <strong>River</strong>, Port <strong>Newark</strong>, and the area<br />
north of Shooters Island. A variety of processes were thought to be contributing to the high rates<br />
of deposition in these areas. For example, the density-induced circulation pattern in the lower<br />
<strong>Passaic</strong> leads to the downstream transport of particles from the upstream <strong>Passaic</strong> <strong>River</strong> in the<br />
surface layer; settling of these particles such that they mix with lower layer sediment and are then<br />
transported in a net upstream direction in the bottom layer, a process which increases the residence<br />
time of the particles in this region, thereby promoting sedimentation. Alternatively, the enhanced<br />
deposition in the Port <strong>Newark</strong> area was attributed to what was described as “scouring and settling<br />
lag effects” in a closed-ended channel. Finally, a high influx of solids from the Kills, combined with<br />
low current speeds and extended slack water periods (as long as 2 hours) were thought to be the<br />
cause of enhanced deposition in the area north of Shooters Island (Suszkowski, 1978).<br />
The preceding phenomena provide a useful working model for how to represent the<br />
processes that control sediment transport in the <strong>Passaic</strong> <strong>River</strong>-<strong>Newark</strong> <strong>Bay</strong> system. Planned<br />
evaluations with a high-resolution model will further elucidate the importance of these and other<br />
processes that are controlling sediment deposition in these localized areas. Initial diagnostic testing<br />
with the model will be needed to define the level of grid resolution that is required to represent these<br />
fine-scale features. It may ultimately be necessary to unify these different model grids to obtain a<br />
finalized overall model calibration for the system. However, separation of these analyses for initial<br />
model development purposes will allow for more computationally efficient model runs to be<br />
performed during the initial stages of model development.<br />
1.6 CONCEPTUAL SITE MODEL (CSM)<br />
The purpose for developing a CSM is to establish a clear relationship between site-specific<br />
conditions and the types of models that are to be applied. The CSM should describe, in as much<br />
detail as possible, each of the important physical, chemical and biological processes that are<br />
operative at the site of interest. This will help to ensure that the models to be applied will be<br />
suitable for their intended use, at least to the degree that the current understanding of the system<br />
permits. The CSM will typically include consideration of hydrodynamic processes, sediment and<br />
contaminant fate and transport processes, as well as biotic processes. While many of the important