TOLEDO, Ohio – On average, two big ships call every day at the docks of this Lake Erie city. The route to one of the busiest ports in the Great Lakes follows a 34-kilometer (21-mile) ship channel, which starts well out in Lake Erie, runs past the Maumee River delta, and ends 11 kilometers (seven miles) upstream. To ensure the ships do not scrape the bottom of the shallow port at the mouth of the silty Maumee, the U.S. Army Corps of Engineers annually dredges 700,000 cubic meters (900,000 cubic yards) of mud and sand from the channel, or 1 million metric tons a year.
For decades, the mathematics of waterborne transport here were simple. For every 10 to 11 metric tons of cargo that moved into and out of the Toledo port, about one metric ton of sediment left the channel. (Last year, 10.4 million metric tons of cargo were handled at the port.)
But with climate change, the equation is almost certain to get more complex and more expensive, say scientists and port managers. More mid-winter snow melts and rainstorms – and more frequent heavy rainfalls, especially in spring – may lead to higher soil-erosion rates, meaning that Great Lakes rivers are likely to carry more soil into harbors. Higher air temperatures already are warming the Great Lakes, blocking ice from forming, and increasing rates of evaporation that may lead to lower lake levels.
This all equates to more frequent dredging to keep transportation flowing on the Great Lakes. Tens of millions of dollars in Great Lakes port planning and construction depend on a better understanding of weather and water conditions over the next several decades. Tens of billions of dollars in waterborne trade do, as well.
Rivers in the Great Lakes Basin deposit 2.3 million cubic meters of silt annually into the region’s major ports. Of the 1.5 million cubic meters that the U.S. Army Corps of Engineers dredges annually, a little less than half is dredged from the Toledo ship channel alone, due to the super silty Maumee River.
Click image to enlarge.
In Toledo, the careful choreography – between ships that carry cargo into port and barges that haul equipment and dredge spoils out of the eight-meter (27-foot) deep channel – describes an essential dance of commerce that is decades old. The Maumee River, which drains productive farmland in Ohio and Indiana, carries a huge sediment load, depositing much of it in the Toledo port, at its mouth.
Great Lakes ports, harbors and marinas are vulnerable to several potential climate change conditions, the most relevant and potentially most costly are water level variability outside normal ranges and storm intensity. Both rising and falling water levels can impact infrastructure stability and strength, as well as requiring additional channel dredging. A major impact of lower lake levels is the potential for harbor infrastructure decay as structural elements are exposed to oxygen (Clark, 2013).
Adaptation strategies for Great Lakes ports, harbors and marinas to potential climate change must be considered and implemented if applicable. Otherwise, structure failures are only a matter of time. Structures must be designed with potential climate change impacts in mind. A detailed risk assessment can be completed to compare the economic, social and natural resource risks of such structures with the potential impacts and timing of the climate change variables (Clark, 2012; Bergeron and Clark, 2010).
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This story was adapted from the original article “Great Lakes Ports and Shipping Companies Confounded by Climate Changes and Water Levels” written by Keith Schneider, 2012, Circle of Blue