In 1987, a dyke was completed along the riverfront to protect the town from flooding. The dyke is designed to withstand a 200-year flood, an event that would raise water levels even higher than in 1979. In the late 1980s Water Resources developed a model to help forecast when break-up will occur and whether flooding is a concern. They consider factors such as the thickness of the ice and the timing of the spring thaw and daily changes in water level. Janowicz says that the ringing of the bell on the tripod just signals the start of breakup.
Water flowing out of the Klondike River often causes an initial shift in the ice.
But it is water from the Stewart and White Rivers that finishes off the job, and sometimes causes flooding. Once breakup has started in Dawson, staff from Water Resources keep a close eye on conditions both upstream and downstream of Dawson, keeping track of where the ice is running and how snowmelt is progressing. They also use satellite images to monitor conditions in the area. Every day they fly over the section of river between the Chandindu and White Rivers. The White, which drains the western St. Elias Mountains, is warmed by coastal flows of milder air from the Pacific, and can open up as much as two weeks before the Yukon River.