Development of a Physically Based Sediment Transport Model for Green
Bay, Lake Michigan
Abstract
Green Bay is the largest freshwater estuarine system on earth, drains
one-third of the Lake Michigan basin and delivers one-third of the
lake’s phosphorus load. Southern Green Bay is a designated area of
concern (AOC) due to ecosystem degradation that includes eutrophication,
harmful algal blooms (HABs), hypoxia, lost or altered habitat, and
reduced water quality. While marine estuaries are subject to tidal
influence and saltwater intrusion, this freshwater estuary is subject to
lake intrusion of freshwater with different quality parameters.
Understanding the simultaneous effects of tributary flows and lake
intrusions is crucial to comprehend the dynamics of freshwater
estuaries. A single hydrodynamic, wind-wave, and sediment transport
model was developed for the lake and its estuary. This approach provides
fine resolution in the estuary and simulates directly the combined
effects of tributary flows and lake intrusions. The approach overcomes
open-boundary limitations of nested models, and of whole-lake models
that lack sufficient resolution or wind-wave and sediment transport
simulation. The model confirms findings of previous studies and
demonstrates how the circulation, thermal regime, wave action, and
sediment transport in the estuary depend on meteorological forcing,
tributary flows, and lake intrusions. The stage is set to apply this
approach to study biogeochemical processes in lakes and estuaries.