Kennedy is a lawyer with the U.S. National Resources Defense Council and president of the Waterkeeper's Alliance.
He was to tour an oilsands plant in the Fort McMurray area this weekend and visit a First Nations community at Fort Chipewyan.
David Schindler, a University of Alberta water expert, says Kennedy didn't want to criticize the oilsands while people work to cope with the floods that have ravaged Calgary and other parts of southern Alberta.
Schindler says Kennedy made his decision after hearing of the derailment of the Canadian Pacific petroleum tanker cars on a rail bridge over the Bow River.
Kennedy, who says the oilsands have serious implications for human health and the environment, has not set a new date for the trip.
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