Living with the Lakes

Workshop addresses concerns in Wisconsin harbors and marinas

Decrepit breakwaters, low lake levels and limited funds for dredging topped the challenges to Wisconsin’s Great Lakes harbors and marinas addressed at a workshop sponsored by UW Sea Grant and the Bay-Lake Regional Planning Commission’s Harbor Council.

Held on the UW-Green Bay campus March 22, the workshop featured nine speakers and attracted 45 marina operators, contractors, engineers and staff from the Wisconsin departments of Natural Resources and Transportation.

Breaking waves 16-20 feet high formed outside the Duluth/Superior Harbor Nov. 27, 2001.  Such waves can be treacherous for small watercraft.  Photo courtesy of Joel Peterson, Minnesota Pollution Control Agency.

Philip Keillor summarized the predicted long-term effects of global climate change on Great Lakes water levels. Most modeling suggests low lake levels will be common in the future. These may include record low levels and intervals of high water levels, said Keillor, UW Sea Grant’s coastal engineering specialist.

Low water levels reduce the cargoes commercial ships can carry and may cause large waves to break before they reach harbor entrances, Keillor said.

Doug Zande, chief of operations for the Detroit District of the U.S. Army Corps of Engineers, gave an overview of the Corps’ budget and priorities.

About $52 million of the operations and maintenance budget is being spent in the Great Lakes this year, Zande said. Thirty to 40 percent of that goes toward maintaining the Soo Locks and navigation channels connecting Lakes Superior, Huron and Erie.

A close second priority is maintenance dredging of commercial harbor entrances and channels, he said. Twenty-five to 30 percent of the Great Lakes budget is devoted to Wisconsin, including the Duluth/Superior harbor, one of the busiest in the country.

A breakwater section in Racine Harbor.  Timbers are exposed to air beneath the concrete caps, and the supporting rip-rap has fallen away from the structure.  Photo courtesy of Baird and Associates Coastal Engineers.

The Corps is concerned about possible catastrophic failure of aged and weakened breakwater sections during severe storms, Zande said.

Many breakwaters on the Great Lakes are made of wooden “cribs,” boxes that are filled with stone and then capped with large concrete sections. Others employ timber piles driven into the lakebed. Timbers that remain submerged in the Great Lakes’ cold water are believed to last indefinitely.

However, when water levels are low, parts of these wooden structures are exposed to air and they deteriorate. If they fail, the rock piles may wash away, leaving no support for the concrete caps.

The Corps has reinforced many of these rotting timber cribs with steel sheet pile, and they are believed to be strong. Others remain vulnerable to failure during high wind and wave conditions, Zande said.

These concerns were echoed by representatives from Baird and Associates Coastal Engineers, and Coastal Planning and Design. The two companies showed numerous slides of deteriorating timber piles; rotting, ice-damaged harbor dockwalls; and broken, unsafe walkways and pavement.

Participants also raised concerns about habitat degradation. Fish and wildlife habitat in the Great Lakes has been lost to shoreline development, dams, and dredging, according to Vicky Harris, UW Sea Grant’s water quality specialist. Other causes include vertical walls and shoreline hardening, which reflect wave energy and increase erosion.

One solution is “soft engineering,” which uses vegetated, gently sloping shorelines to control shore erosion. Soft engineering can also help restore shallow water habitat and barrier islands that erode during high water and storms, Harris said.

- Philip Keillor and John Karl

Last updated 24 April 2002 by Karl
All contents copyright 2001 University of Wisconsin Sea Grant Institute

http://www.seagrant.wisc.edu/Communications/news/LD_stories/2002/LivingWithLakes.html