A Nov. 27, 2001, photo depicts wave heights likely in excess of 20 feet. Plunging breaking waves in harbor entrances have become an increasing problem in western Great Lakes harbors as water levels have declined.
Credit: Kenneth R. Newhams, Duluth Shipping News
During the night of Nov. 26, 2001, and all the next day, a storm blew over western Lake Superior. At Devils Island Light (34 m or 112 feet above the lake, 105 km or 65 miles NE of Duluth), from 3 p.m. CST on Jan. 26 and all day on Jan. 27, winds blew from 50-60 degrees at 37-49 mph (17-22 m/s) with gusts of 45-59 mph (20-26 m/s). All day on Jan. 27, the Sky Point Harbor anemometer on Minnesota Point measured winds of 37-40 mph (17-18m/s) with gusts of 52-55 mph (23-25 m/s).
The laker Edwin H. Gott went to anchor near Rock of Ages Light while the John G. Munson found shelter along the north shore. The small ocean freighter Voorneborg arrived in Duluth-Superior sometime during the night and anchored inside the harbor (1). During the storm, the Canadian CSL’s Tadoussac departed the ship canal (2). Partially plunging breakers just outside the canal entrance had crests at, and above the high parapet wall (3) of the Duluth Entry lighthouse.
The top of that parapet wall is 18 feet (5.5m) above SWL of late November 2000(4). Therefore, observed waves must have had crest elevations that were 18 to 21 feet (5.5-6.4m) above SWL. Crest-to-trough wave heights were 23 to 26 feet (7-8m), assuming Cnoidal wave profiles with troughs below SWL 25% of elevation above SWL (5). The plunging breaker in the photograph was probably larger than the waves shown in other photos, rolling through the ship canal.
The 25-year design storm wave conditions off Duluth are deepwater wave heights of 23 feet and wave period of 11 seconds (6). Another source indicates 50-year design storm waves of 24 feet (7.2 m) having an 18 percent chance of occurrence in a 10 year interval (7).
The water level at Duluth rose over 1.3 feet during the storm, according to the U.S. Army Corps of Engineers water level gauge (4).
A view of the timber lake walk damaged by a Nov. 26-27, 2001, storm. Some of the board sections had been moved landward over an adjoining asphalt path, itself washed out in some spots.
Credit: Joel Peterson, Minnesota Pollution Control Agency
Photo of the storm
Temporary repairs kept the Duluth Lakewalk open during the winter. Permanent repairs costing $201,000 are were completed before the following summer (8). Repairs were made to about 100 yards of boardwalk, as well as replacement of some washed-out asphalt pavement, some revetment stone that slid into the lake and some ornamental fencing.
A 400-foot section of the revetment protecting the Duluth Lakewalk slumped toward Lake Superior.
Credit: Gene Clark
Sources:
1. Great Lakes/Seaway Log. 12/3/01. Vol. 29, No. 25.
2. Photo courtesy of Kenneth R. Newhams, Duluth Shipping News.
3. Photo courtesy of Joel Peterson, Minnesota Pollution Control Agency.
4. Information and photos from Gene Clark, Minnesota Board of Water and Soil Resources.
5. Robert L. Wiegel. 1964. Oceanographical Engineering. page 47.
6. Baird and Associates. 1994. Bayfront Development Duluth, Minnesota. Extreme Design Criteria. Draft report for City of Duluth and RREM, Inc.
7. Hindcast Wave Information for the Great Lakes: Lake Superior. January 1992. By David B. Driver, Robin D. Reinhard, and Jon M. Hubertz. WIS Report 23. Waterways Experiment Station, U.S. Army Corps of Engineers.
8. Great Lakes/Seaway Log. 4/15/02. Vol. 30, No.8
