Great Lakes Dredging Team Webinar Offers New Tools, Identifies Trends
The Great Lakes Dredging Team webinar April 3 provided information about weather trends and new tools for predicting the erosion that necessitates dredging.
The team includes representatives from the Corps of Engineers along with other federal, state and municipal agencies and interested stakeholders. It typically meets once a year via webinar and once in person. The next in-person meeting will be September 24-26 in Erie, Pa.
Ice Cover
James Kessler of the National Oceanic and Atmospheric Association’s Great Lakes Environmental Research Laboratory kicked off the meeting by talking about ice cover on the lakes.
The laboratory has ice cover data available going back to 1973. At its maximum, about 40 percent of the Great Lakes are covered with ice in a typical year, although that has been as much as 90 percent or as little as 10 percent in the past, Kessler said.
The U.S. National Ice Center and Canadian Ice Service use satellite radar, which is cloud-penetrating, to determine the amount of ice. Once collected on paper charts and distributed weekly, the information is now available online daily. It includes information about ice thickness as well as land-fast ice that might be of interest to dredgers as ice along the shore restricts wave action that can lead to sediment erosion, Kessler said.
In general, Kessler said scientists have noticed that over the whole of the Great Lakes, ice is decreasing by about 6 percent per decade.
“But we’re still experiencing variables,” Kessler said. That included 2014 and 2015, which were both heavy ice years.
The number of days in which the lakes are at least 10 percent covered with ice is also decreasing, he said, at a rate of 0.7 days per year on average. The year 2024 had the fourth lowest amount of ice at its maximum—usually determined to be in late February—on record; however, this season topped the record books in having the lowest seasonal average amount of ice.
Coastal Processes
Jim Selegean, a hydraulic engineer with the Detroit Engineer District, said in his presentation that roughly 90 percent of sediment moved in the Great Lakes does so during the five biggest storms during the season. The worst of those storms typically take place during the winter months, he said.
Conditions during these storms make evaluating sediment movement particularly tricky, he said, because the intensity of the storm and wave action make it unsafe for in-person assessments and tend to impact sensors and measurement buoys.
Those assessing conditions noted that sediment movement increases during periods of higher rainfall and that 2020 broke all records.
“When it hits these peaks, problems start happening,” Selegean said.
Climate scientists predict “higher highs and lower lows” and that those patterns of variation will come more quickly, he said.
He noted that the waves during high-water periods erode bluffs and move sediment but that there needs to be more research on whether ice acts as shore protection or as an agent of erosion.
New Assessment Tools
Jesse McNinch and Rachel Malburg, both of the Detroit Engineer District, talked about the Integrated Radar Monitoring System (IRAMS), as a new tool that can be deployed for rapid coastal measurements during storms.
The system measures shoal movement, wave parameters and currents.
An IRAMS system costs less than $10,000, can be rapidly deployed by one or two people and sends data directly to users’ cell phones, McNinch said.
It provides real-time, high-resolution information about shallow environments during adverse conditions using hardware he described as rugged.
IRAMS can monitor can track movement of shoals and sandbars in navigation channels to be a rapid aid to navigation and targeted dredging, McNinch said.
Malburg gave examples where the IRAMS system has been used, including determining the optimal placement for beaches using dredged materials. McNinch said it has also been helpful in validating wave runup and flood models and monitoring wave detection. He believes it can be successfully used to determine the location and intensity of where rip currents will be located along manmade structures such as piers.
“We think the system can be a life-saving measure,” he said.
However, he noted that the system does not replace the precision of traditional acoustic depth measures or using a boat under calm conditions.
Another new tool now available is the Corps Shoaling Analysis Tool (CSAT).
Paul Cocca, water management section chief for the Buffalo Engineer District, provided an overview of the tool, which can be used for planning channel maintenance. It is available online at https://cirp.usace.army.mil/products/csat.php.
The tool uses historical channel surveys to forecast shoaling rate statistics by reach, allowing for dredge volume forecasting.
However, Cocca cautioned, “The output is only as good as the input.”
He said those making use of the tool should make sure that all eHydro surveys have been included, check survey data, check for missing dredge events and check for any potentially falsely identified dredge events before relying on CSAT’s data.
