River Basin Characteristics
The Lower Maumee River flows northeasterly from Waterville, Ohio, to the Maumee Bay of Lake Erie, and discharges to a Federal navigation challen at Toledo Harbor in Toledo, Ohio. It is the major tributary to the Western Lake Erie Basin (WLEB) and transitions from a shallow, fast-moving river upstream to a deeper, slower-moving river, while experiencing a wide range of flows throughout the watershed. The time of travel in the lower river from Waterville to the bay is very short during high flow (approximately one day), leaving relatively little time for suspended solids to deposit in the river before entering the bay.
Toledo Harbor receives the largest amount of sediment deposition of any Great Lakes harbor, with these sediments coming predominantly from the Maumee River watershed. The broader Maumee River basin contains eight major subwatersheds, which drain portions of counties within Ohio, Michigan and Indiana (6,354 square miles). This area contains roughly 85 percent agricultural land use. The Toledo Harbor navigation channel receives between 850,000 and 1,250,000 cubic yards of sediment per year.
As one of the Great Lakes Restoration Initiative’s priority watersheds, the Maumee River is targeted for a 1 percent reduction in sediment accumulation (relative to the 2008 baseline) by 2012, and a 2.5 percent reduction by 2014. These targets are to be accomplished through soil erosion reduction activities that have been implemented in the watershed since the establishment of the GLRI in 2009.
The objective of this project is to combine the Lower Maumee River – Maumee Bay – Western Lake Erie Basin (LMR-MB) sediment transport model with the Corps’ monitoring of bathymetry in the Toledo Harbor navigation channel andsuspended solids monitoring at Waterville, Ohio, to develop and apply a process for tracking the GLRI annual sediment deposition metric for the Maumee system.
The LMR-MB model was originally developed by LimnoTech under a previous project for the USACE-Buffalo District to simulate hydrodynamic, wind-wave, and sediment transport processes at a variety of temporal and spatial scales (including navigation channel deposition) for the Lower Maumee River – Maumee Bay – Western Lake Erie system. This LMR-MB model was developed using a suite of public domain modeling tools, with additional enhancements to the sediment fate and transport sub-model to improve model stability and efficiency. The Environmental Fluid Dynamics Code (EFDC) model was selected to serve as both the hydrodynamic sub-model and the sediment transport sub-model. EFDC is an open source, public-domain model code developed and supported by the U.S. EPA. The Simulating Waves Nearshore (SWAN) was selected as the wind-wave sub-model. The Sandia National Laboratory EFDC (SNL-EFDC) algorithms were used for the sediment transport sub-model. The linked modeling framework comprised of EFDC, SWAN, and the SNL-EFDC sediment transport sub-model, is collectively referred to as the “Lower Maumee River – Maumee Bay” (LMR-MB) model.
Modeling was completed and a training workshop for state and local partners was held in July 2013.
Use and Applications
The LMR-MB model was applied to simulate sediment delivery and deposition dynamics for a suite of scenarios designed to address the management objectives. The primary focus of the scenarios developed was to quantify the reduction in sediment deposition in the Toledo Harbor navigation channel during the 2009-12 period relative to the earlier 2006-08 period. Additional scenarios were designed and implemented to quantify (via the model) the relative contribution of the various sources of sediment that contribute deposition in the navigation channel. The Total Suspended Sediments (TSS) concentration time series were incorporated into the LMR-MB model, and simulations were designed and implemented to evaluate reductions in navigation channel deposition for the Toledo Harbor system. The key finding of this analysis is that the overall post-2008 reduction in Toledo Harbor navigation channel deposition was 10 +/- 6 percent, which suggests that the GLRI sedimentation target of a 2.5 percent reduction by 2014 has already been achieved.
The success of the integrated model development, calibration, and application efforts for this project has important implications for other Great Lakes river-harbor systems outside of the Western Lake Erie Basin. In particular, the approaches and implementation steps developed for the Toledo Harbor pilot evaluation could be transferred to other major river-harbor systems where reductions in sediment deposition are a high priority.
- Ecology and Environment, Inc.
- U.S. Geological Survey
- Heidelberg University
- University of Toledo