CHICAGO USES WAVE MACHINE

A Wave Machine that simulates natural lakefront conditions is preventing erosion of our shoreline, flooding of Lake Shore Drive, and preserving the beauty and utility of our beaches, says Paul Freedman, Principal Assistant Engineer of the Chicago Park District.

In 10 days of operation under the stands at Soldier Field the Wave Machine simulates a 10-month effect of wave and wind action on our natural shoreline. The purpose is to determine how and where jetties are to be built. A jetty is a steel, concrete, wood, or rock structure that projects out into the water to break up wave action and prevent erosion of the shoreline. This process is a long-range money saver, because it prevents unnecessary expenditure of funds for jetties that would not prove effective.

The Chicago Park District follows a seasonal testing pattern from late winter through spring, summer and fall. At Columbia Street end beach, currently under test, boats pulling long cables put a grid system out into the lake to determine points at which soundings are to be taken. The purpose is to see what happens at specific points on the lake floor as a result of wind and wave action. Sonar equipment makes soundings for depths, and distances out into the lake are measured instantly by electronic measuring devices.

Wave action resulting from wind, soundings of the specific beach, and a duplication of the grid system are reproduced in the wave tank. A proposed jetty design is installed in the wave tank to see if it would be effective in warding off wind and wave action simulated from the natural beach under test.

Wave heights of 5 feet as if generated by a northeast wind are simulated for 72 hours; wave heights of 5 feet as if generated by a due east wind are simulated for 72 hours; and finally wave heights of 5 feet as if created by a southeast wind are simulated for 96 hours. At completion of each phase of testing in the wave tank, the simulated beach is sounded, photographs are taken, and the new shoreline resulting from wave and wind action is recorded on log sheets. This information goes to the structural engineer, C. James Wolfe, for study to determine the placement and type of jett/ to be built.

The beaches between North and Fullerton Avenues, the reconstructed Oak Street Beach, with its Michigan Avenue underpass, and the jetty that protects the 59th Street harbor entrance were based on tests made in the wave tank. Not only are existing beaches tested, but new beaches such as our present 31st Street beach are built after similar testing. Ohio Street Beach will be next to be reproduced in the wave tank in a continuing program of the Chicago Park District to keep our lakefront a showplace of the nation.

July-August 1970 Illinois Parks 111