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Corps monitoring Mill Creek; flooding is unlikely

The man-made bend in Mill Creek. MYCB photo by Dan Thesman.

WALLA WALLA, Washington – There’s an above normal snow-pack in the Blue Mountains and that means the U.S. Army Corps of Engineers is keeping a close eye on the amount of water the melting snow is producing.

“What we’re monitoring as we go forward into the future is how rapidly the temperatures warm up and whether or not we’re going to get additional precipitation – rain,” USACE Regional Reservoir Manager Steve Hall said. “Events that will come through and melt that snow-pack at a faster rate than normal.”

As part of that, he monitors the jet stream in the Pacific Ocean.

“Because we can get what’s called an atmospheric river, and that is basically where the jet stream is coming off the Hawaiian Islands, that general area, and it comes directly in,” Hall said. “(It) brings a lot of moisture and warm air and that will change our temperatures. It can drive that up to 60 or 70 degrees and raining. And that’s what causes the biggest floods.”

Snow-melt is a given and Hall said that will cause higher flows in the Mill Creek channels. As the Corps continually monitors Mill Creek, Hall said water will be diverted to Bennington Lake if flows exceed 1,400 cubic feet per second. Hall said that’s when the Corps starts to see damages downstream, mainly erosion to the channel banks beyond the leveed sections of Mill Creek.

“Normally we have to have frozen ground to have a really, really big flood like we had in 1996,” he said. “We don’t have that right now, so the risk of flood is fairly low as we go forward into the spring this year – but we may have diversions into the dam.”

Filling Bennington Lake for recreational use will probably happen in mid to late April.


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