During a marathon race, competitors must get out of their canoes and carry them a short distance on land before putting them back in the water.
It was during the fourth of five portages on the 26.2-kilometre course that Andersson capsized while launching her canoe, which filled with water.
The Swede, who was the reigning world champion, managed to empty the canoe completely only after the final portage. But the gap to the top three was too large on the final lap, and Andersson finished fourth.
Last Friday, Melina Andersson won a historic gold medal in the short-track speed skating event. It was the 27-year-old's eighth World Cup gold medal of her career - a record for a Swedish canoeist.