ASK THE METEOROLOGIST
“How do floods happen?”
Kason, 3rd Kennedy Elementary
Floods are, of course, caused by too much rainfall in either a short amount of time, or too much rain without a place for it to drain. Sometimes it’s a combination of the two. In this instance, we are going to talk about what we get when heavy snow falls on frozen ground, followed by many inches of heavy rain and warmer temperatures.
All of these factors combined lead to one of the most historic weather events over the past century in Oregon. The Christmas Flood of 1964’s 50th anniversary is this year, and today marks the beginning of that chain of events which led to the record flood. Snow began falling this same day 50 years ago, then rainfall followed on the 20th, which in turn melted some of the snow that had just fallen. The snow fell on frozen, hard ground, meaning that the soil could not absorb the rain that followed the snow. In addition, there were anywhere between 5 and 20 inches of rainfall on top of the snow, which created several inches of snow melt as well. All of this water had to have some place to go, and when it reached the rivers, the water was more than they could hold.
The Christmas Flood caused 17 deaths in Oregon. Almost every river in the state rose above its banks, and the end result was damage topping hundreds of millions of dollars throughout the Pacific Northwest. It’s been called a once in a century event, and even though we’ve seen significant floods since, they don’t quite compare to that flood we saw 50 years ago.
Chief Meteorologist Kate McKenna