Under the Great Lakes Tributary Modeling Program (GLTM), the U.S. Army Corps of Engineers develops tools for federal, state, local, academic, and private sector partners to assess sediment transport and delivery for tributaries discharging to federal harbors and the Great Lakes Areas of Concern. These tools inform decisions about the development of lands and the use/placement of soil conservation and nonpoint source pollution prevention measures.
Tributary-specific models developed under the GLTM Program are utilized by partners for navigation maintenance planning, watershed and ecosystem planning, forestry management, and water quality compliance evaluations.
These models are used to help communities keep soil on land and out of waterways, prevent reduced water depths in harbors and shipping channels that cause groundings and unsafe conditions. They can also support state and local measures to reduce or prevent sediment loadings in tributaries and lakes, by helping minimize soil erosion and nonpoint source pollution (nutrients) and their adverse impacts to the Great Lakes, such as the size and frequency of algal blooms and dead zones, which can limit recreational use of the lakes and impact fish habitat.
Examples of Use
- Model developed for the Calumet River (IL) watershed assessed sediment sources and planned Activities of the GLDT structural and non-structural solutions to reduce the input of sediments to the deep draft channel at Calumet Harbor and River (IL/IN). This effort contributed to the development of a comprehensive plan for maintaining this major harbor (3rd busiest on the Great Lakes) for the next 20 years. Currently, 50,000 cubic yards of material is dredged from this harbor annually and placed in the Calumet River confined disposal facility (CDF), which is nearing capacity. Methods to reduce sediment loadings from the river will complement other beneficial use and confined placement efforts underway.
- Modeling, sediment budget, and field data of the Nemadji River (MN/WI) facilitates a better understanding of the causes of sediment production and supports long-term forecasting of sediment delivery to the federal navigation channel at Duluth-Superior Harbor.
- Model developed for the Ontonagon River (MI) can forecast the need for (and extension of) maintenance dredging for the federal channel based on annual snow pack, since the majority of sediment delivered from the watershed occurs during spring snow-melt.
- Model developed for the St. Joseph River (MI) was used to determine the cause of several recent large shoaling events in the inner harbor at St. Joseph, including where the sediment came from and whether this is likely to be a recurring problem. Additionally, the model showed material had an appropriate gradation for placement on the beach/nearshore, which is considerably cheaper than traditional upland disposal.
- Ongoing GLTM Dam Capacity Study (basin-wide) supports the assessment of the long-term maintenance requirements of federal navigation channels by providing insight into the remaining storage capacity behind thousands of dams that intercept and store sediment throughout the Great Lakes. As these reservoirs fill, the amount of sediment delivered to downstream navigation channels may increase up to ten-fold, exacerbating existing channel maintenance challenges.