Ice jam leaves area better prepared for runoff

by nathan oster

Three years after the floods of 2011, and just a matter of weeks removed from the ice jams on the Big Horn River that caused flooding between Worland and Greybull, local emergency managers feel like they are better prepared now than they have been in the past for the anticipated spring runoff.

Mountain snow water equivalents (SWEs) are well above average all across Wyoming.

Jim Fahey, a hydrologist with the National Weather Service in Riverton, said the SWEs for the western side of the Big Horn Mountains generally range in the 140 to 145 percent of median. At the Shell Creek site, specifically, it was 134 percent of median on Tuesday.  At Bald Mountain, it was 135 percent of the median.

In terms of the amount of snow up in the Big Horns, Faye said the measurements as of Tuesday morning were 89 inches at Bald Mountain, 77 inches at Bone Spring Divide, 75 inches at the snow measuring machine on Shell Creek and 56 inches at the Powder River Pass location.

Fahey said those totals are comparable to the ones at a similar time in 2011, when there was extensive flooding along Shell Creek, as well as 1997, which was another high flow year in the area.

“The Shell Creek Snowtel is running above 2011 levels, and right on the record years of 1997 and 1999, in terms of flow,” said Fahey.

That doesn’t necessarily mean that there will be flooding this spring.  As Fahey points out, it all depends on how quickly it warms up — and whether the area receives any significant spring rainfall.

“Mother Nature usually gives us a break on runoff, in that we’ll generally see a little warming in April that takes the edge of the pack,” he said. “Then it’s just a matter of seeing what we get through the rest of April. It can be a snowy one, too, as we all know.”

Fahey said Shell Creek “can handle a pretty good pack,” unlike smaller tributaries such as Medicine Lodge Creek, Paintrock Creek, Ten Sleep Creek and the upper parts of the Nowood, which are more susceptible to flooding.

Ernie Smith is the emergency management coordinator for the town of Greybull.

“Based on the SWE and the snowfall in the high country, the spring runoff is a concern, especially if we have several days of hot weather,” he said.

He was asked how this year stacks up against 2011.

“We’ve had a little colder weather, and I think higher-than-usual snowfall, so the SWES are a little higher than they normally are.  But the big thing on that is, this year, with the ice jam situation that we had, we are so much better prepared to do things because of the sense of  urgency that the ice jams put on us.”

For example, there remains a 500-foot stretch of Jersey barriers atop the Greybull levee.

Several Hesco barriers are also in close proximity, having been moved here from a warehouse in the Midwest by the U.S. Army Corps of Engineers.

“Plus we have several hundreds, if not thousands, more sandbags than we had in 2011,” he said, citing among other things 48 pallets, each of them containing 40 sandbags.

On top of that, Smith said “We have a lot better monitoring system now than we did in 2011 … and even since the ice jams.”

As for local residents, they, too, are likely better prepared, having lived through the recent ice jams, he said.

Shell Fire Chief Mike Nelson said his department has a lot of sandbags — both empty and full — and that preparing for the spring runoff has been a major topic of discussion at recent LEPC meetings.