Arrow-right Camera
The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Greatest snowmelt flooding was in 1948

The Spokesman-Review

A regular reader recently asked when the worst floods occurred in this part of the country.

Well, that question can be easily answered by numerous area geologists, including Jim Pearl of Hayden, Idaho, and Tye Parzybok of Missoula.

Parzybok writes in his engrossing recent book, “Weather Extremes of the West,” “The greatest floods on earth in recent geologic times tore through western Montana, northern Idaho, eastern Washington and the Columbia River Gorge about 13,000 years ago near the end of the last Great Ice Age.”

He went on to add: “Known as the ‘Great Spokane Flood,’ the Bretz Floods, or the Glacial Lake Missoula Floods, these floodwaters originated in a huge deep lake that inundated much of western Montana.” (I might add that Flathead Lake between Polson and Kalispell remains today one of the biggest lakes in North America.)

“Tongues of ice from a huge continental glacier dammed the lake until its water level rose enough to float the ice dam like a giant ice cube,” Parzybok wrote. “Suddenly the ice dam broke loose, sending a towering wall of icy water across what is now Spokane (and Coeur d’Alene) and into the Columbia River Basin.

“For days on end, the area that is now Portland, Oregon, lay submerged beneath 400 feet of water. And this happened not just once, but repeatedly. When the lake eventually drained, the glacial ice once again dammed the lake until the water level once more rose high enough to float the dam resulting in more floods that deepened and widened the only significant ‘gap’ in the entire length of the Cascades, the spectacular River Gorge.”

Yes, we’ve seen several major floods in very recent times, but nothing compares to “The Great Spokane Flood” of 11,000 B.C.

However, the greatest spring snowmelt flooding within the last century occurred in May and June 1948 and ranks as second in the all-time for top weather events in Washington. During that time, widespread flooding occurred in North Idaho, Eastern Washington and along the Columbia River. Many area rivers rose as much as 5 to 10 feet above flood stage.

Flooding has now become a big concern with area officials due to the heavy snowpacks in the mountains and in the lower elevations. The next two to three months will be critical as far as local weather patterns are concerned. The best-case scenario is to have below normal moisture along with warm days and cool nights. This gives the ground and streams a chance to absorb all of the extra water. The worst case scenario is warmer than normal temperatures, combined with lots of rain and wind. Those type of conditions will melt snow very quickly that will lead to widespread flooding, especially if accompanied by torrential downpours.

Since last week, the area has seen a major weather pattern change. Prior to the second week of February, we endured two six-week cycles of snowier and colder than normal conditions. This new weather cycle should be drier and a bit warmer than average. The next weather change should arrive around late March and early April as our region should turn wetter once again.

Temperatures may be well above normal levels in early to mid-March with readings challenging the 60-degree mark. Again, let’s hope we don’t see all that snowmelt in a very short period of time. If one lives near a stream, it’s very likely that you’ll see some extensive flooding within the next few months.