With nine days left before the total solar eclipse passes over Central Oregon, emergency managers for the region’s three counties have turned to an informal measure to shed some light on the largest unknown associated with the rare celestial phenomenon.

An online survey by the Central Oregon Emergency Information Network, which as of Friday had been completed by more than 1,500 people from outside the region, is designed to help officials and businesses plan for when they should expect visitors, and how long they might stay.

However, even the survey designers acknowledge the numbers are far from perfect. Voluntary surveys are not the best way to predict something.

“You certainly wouldn’t want to go to the lottery with these numbers,” said Nathan Garibay, emergency services manager for the Deschutes County Sheriff’s Office.

That said, if the survey is to be believed, the most startling prediction has to do with the estimated 200,000 people coming for the eclipse. The estimate might be low.

For months, officials have estimated the number of people coming to the three-county area during the eclipse by using hotel and campground reservations and attendance at ticketed events, like Oregon SolarFest in Madras, to help them count. However, those numbers don’t provide much insight to visitors who are camping on public land or staying with friends and family, according to Garibay.

“It’s a really large, uncoordinated event,” Garibay said.

The emergency information network, made up of local, state and federal partners who will be providing updates during the eclipse, began developing a visitor survey in March, according to Michael Ryan, emergency manager for the Crook County Sheriff’s Office. The survey has five questions, oriented around how long visitors will be staying in Central Oregon, where they’ll be sleeping and what events they’ll be attending during their time in the region.

“We have no way to quantify that,” Ryan said. “And that’s been the hurdle here.”

Garibay added that the Central Oregon Emergency Information Network and the agencies that comprise it used a mix of online channels to promote the survey, including Facebook and Twitter pages operated by the agencies, Reddit and That Oregon Life, a lifestyle blog aimed at Oregon residents. The survey went live on June 30.

While Garibay said the network is still collecting and aggregating survey data, the results have stabilized in recent weeks, and became statistically sound once around 700 people responded. From there, he said the county’s emergency managers began sharing the survey data with members of the public, including business owners, in recent weeks to help them for the crush of people expected to arrive.

As of Monday, the survey indicated that 11 percent of respondents are planning to arrive on Aug. 21, the day of the eclipse.

Additionally, 22 percent of respondents are planning to arrive on Saturday, Aug. 19, with another 22 percent arriving on Sunday, Aug. 20.

Perhaps the biggest concern for county officials is when visitors will be leaving, and officials are bracing for a mass exodus on Monday after the eclipse ends. As expected, the survey indicates that the first two days of the week will see the bulk of departures, with 42 percent and 37 percent of respondents indicating they’ll leave on Monday and Tuesday, respectively.

Ryan said that perhaps the biggest revelation from the study is that the number of visitors planning to stay with friends and family is higher than they anticipated.

He said Crook County was counting on around 10 percent of visitors staying with friends and family. As of Monday, 28 percent of respondents were making those plans, which could mean that the region might see more people overall than expected.

Still, there are reasons to be skeptical of the numbers in the survey.

The 1,531 people who had responded to the survey at last count represent just 0.7 percent of the 200,000 people expected for the eclipse. While Garibay said the network put the survey in front of a lot of people, he acknowledged that plenty of visitors won’t be familiar with it.

Like all voluntary surveys, this one could be susceptible to skewed results. In this case, Garibay said that the survey will likely undercount people who decide to visit Central Oregon at the last minute.

“People who aren’t planning ahead probably won’t take a survey,” he said.

Garibay said the numbers shouldn’t be treated as gospel, but rather as a rough sketch of what types of trends to expect. For example, that the survey showed that more than 40 percent of visitors will be driving more than six hours to get to Central Oregon for the event, suggesting that traffic from the Willamette Valley might not be the most significant factor.

Mark Carman, emergency management coordinator for Jefferson County, said he’s included the data in his public presentations over the last two weeks, which has helped business owners and other residents better understand what’s coming.

“It’s been a good tool,” he said.

Additionally, Garibay said the higher-than-expected number of people who won’t be attending any specific event suggested that the sheriff’s office needs to disperse officers around the county, rather than keeping them concentrated at large events.

“You have to present the numbers in context,” he said of the survey results.

—Reporter: 541-617-7818, shamway@bendbulletin.com