The high, fast-flowing Cedar River has helped turn Lake Washington into a risky place for boaters.

The King County Sheriff Department cautioned that the Cedar, which flows into the south end of the lake, and the Sammamish River, which empties into the north end, have washed an unusually large number of logs, deadheads, stumps and other debris into the lake this spring. The debris, when struck by boats, water skiers and personal watercraft, can be dangerous.

“Boaters should note that lakes, especially Lake Washington, could be extremely hazardous for the near future,” said John Urquhart, a Sheriff Department spokesman.

The hazards sometimes are submerged just below the surface, he said.