Search

Previous studies have shown that the western basin of Lake Erie is prone to sediment resuspension due to its shallow depth and abundance of fine-grained sediments. Harmful algal blooms (HABs) caused by the bacteria Microcystis are also common in the western basin and have been shown to overwinter in the sediment layer. Total bottom stress combines shear stress caused by both waves and currents and is the most crucial factor influencing sediment resuspension. Our study utilized hindcasts of hydrodynamic models, specifically WAVEWATCH III (WW3) and Finite Volume Community Ocean Model (FVCOM), to calculate total bottom stress in the western basin of Lake Erie in May-October, 2017-2019. Results showed that wave-induced bottom stress dominated in the western basin, while current-induced bottom stress was smaller but could still cause resuspension during peak events. The highest total bottom stress values were associated with shallow waters (less than 5 m), which included the Maumee Bay and Detroit River mouth. Total bottom stress also varied seasonally, with the most significant values occurring in May and September-October and across years (2019 was less energetic than 2017 and 2018). Future work for this study will seek to identify resuspension events when total bottom stress exceeds the critical shear stress to move the sediment. Calculated bottom stress from WW3 and FVCOM models will also be tested as a potential predictor in retrospective statistical modeling to improve current HAB forecasts in Lake Erie. [ABSTRACT FROM AUTHOR]

The NOAA Great Lakes Operational Forecast System (GLOFS), based on the Finite-Volume Community Ocean Model (FVCOM), provides water forecast guidance across the Great Lakes, however, it does not include harbors and navigational ports. While GLOFS does include inflow from some gauged streams, large volumes of water entering the lakes through tributaries are not being accounted for. To examine the benefits of including model coverage over marine infrastructures, a linked hydrologic-hydrodynamic framework was developed for the Twin Ports of Duluth-Superior in western Lake Superior. Simulated streamflow from the National Water Model (NWM) was injected into an extended wet-dry FVCOM grid that covered the harbor and surrounding floodplain. Test cases were conducted for severe flooding events caused by heavy rainfall and/or storm surges to see if the one-way coupled models could capture coastal flooding. Model results compared well against time-series of water level, with root mean square error (RMSE) and bias values small relative to the typical fluctuations. Inclusion of streamflow for NWM-simulated tributaries improved the accuracy of modeled water levels in the harbor and increased simulated current speeds in navigational channels by up to 0.4 ms-1. Modeled inundation and flood extent in the floodplain closely matched surveys conducted in response to a record flood event in 2012. The results demonstrate the capability of the modeling framework to provide flood guidance in a complex coastal setting in the Great Lakes region. [ABSTRACT FROM AUTHOR]