The Impact of Episodic Events on Nearshore-Offshore Transport in the Great Lakes:
Sediment Resuspension and Transport Modeling
This proposal focuses on the construction and implementation of sediment transport and
particle tracking models to study cross-margin transport in southern Lake Michigan. It is
part of a multiproposal, multidisciplinary program to study the impact of episodic events on
the coastal ecosystem in the Great Lakes. The overall study focuses on an episodic
occurrence of a ~10 km wide plume of resuspended material extending over 100 km along
the southern shore of the Lake Michigan.
An Eulerian sediment resuspension and transport model will be developed for Lake
Michigan by integrating the hydrodynamic model of Schwab and Beletsky (see associated
proposal) with a sediment transport model that includes the effects of wave current
interaction, variable bed properties, and flocculation of fine-grained sediments.
Concurrently, a Langrangian-based particle tracking model will be developed to provide
predictions of particle trajectories and residence times. The primary objectives of this
project are to 1) determine the sediment transport model structure necessary to reproduce
measured cross-shore plume transport and behavior at hydrodynamic scales, 2) determine
the important physical processes affecting cross-shore particle transport, 3) determine the
particle residence time correlation with storm frequency, pattern, and intensity, 4)
summarize the particle transport behavior from source to burial, and 5) quantify the
occurrence of permanent versus transient particle sinks during cross-shore transport. The
models will be tested and verified against the extensive set of field observations (both
Eulerian and Langrangian) that are being carried out as part of this overall program (see
Saylor et al. proposal).
Given the importance of episodic resuspension events to the functioning of the lake
ecosystem, numerical models that predict three dimensional concentration fields of
suspended material as well as track the path of particles in the flow can provide a very
useful management and analysis tool for these lake systems. Currently, estimates of
concentrations and particle residence times resulting from these episodic events are obtained
primarily from limited field measurements, tracer studies, and simple mass balance models.
Development of a fully three-dimensional sediment resuspension and transport model,
together with the detailed field measurements of hydrodynamic variables and suspended
particulate concentrations will allow us to test the ability of these models to reproduce and
predict onshore-offshore exchanges of sediments in large lakes. However, since
conventional Eulerian-based transport models cannot provide information about particle
trajectories and residence times, concurrent development and testing of a Lagrangian-based
particle tracking model is critical for predicting the path that particles take as they travel
cross-shore and for identifying transient and permanent particle sinks along this path.
This collaborative Lake Michigan study provides an ideal framework for model testing and
development. The objectives of our proposed work have been tailored to the goals of the
overall program and its focus on the cross-margin transport of biological, chemical, and
geological materials. Our models provide the basis for further studies and modeling efforts
focusing on the coupling between biological, chemical, and physical processes (e.g. Chen)
and, therefore, provide a critical link in the success of the overall program.