Nature highlights Gustavo Gioia's study of 'drowning machines.'
6/18/2012 By Linda H. Conway
Sign posted near Bow River, Calgary, CanadaHydraulic jumps are a common feature of rivers and waterways, where they can be found close to spillways, weirs, rocky ledges,and boulders. People adrift upstream of a hydraulic jump are liable to become trapped in the turbulent roller of the hydraulic jump. For this reason, hydraulic jumps have been termed “drowning machines” and are recognized as a public hazard.
Written by By Linda H. Conway
Sign posted near Bow River, Calgary, Canada
Hydraulic jumps are a common feature of rivers and waterways, where they can be found close to spillways, weirs, rocky ledges,and boulders. People adrift upstream of a hydraulic jump are liable to become trapped in the turbulent roller of the hydraulic jump. For this reason, hydraulic jumps have been termed “drowning machines” and are recognized as a public hazard. Drowning machines have proven to be so troublesome in highly populated areas that municipalities are having to resort to extreme measures. For example, the city of Calgary, AB, Canada, is currently undertaking a $6.4 million project to eliminate a drowning machine on the Bow River. (See the attached picture, which was shot by Zhongchao Tan of the University of Waterloo, ON, Canada, in August 2010, amid the construction work.) Associate professor Gustavo Gioia, professor Richard D. Keane, and graduate students Stefan F. Gary and Carlo Zuniga Zamalloa teamed up with assistant research professor Pinaki Chakraborty of the Department of Geology to study drowning machines by means of theory and experiments. They have concluded that the average time that a person spends trapped in a drowning machine should not exceed a few seconds, provided that the person remains passive. But far from remaining passive, people will typically swim frantically to stay away from the downward pull upstream of the drowning machine, which is precisely where a chance may be had of escaping by being flushed under the turbulent roller of the drowning machine. The paper appeared in the journal Proceedings of the National Academy ofSciences of the USA and has been featured as a "Research Highlight" in the journal Nature.