County installs concrete barriers as models show 5-foot flooding possible near Elden Road

Jul. 26--A little more than 24 hours after evacuees were allowed to return to their homes of Elden Lookout Road, Elden resident John Harper drove across the nearly six inches of sediments covering some of the roads in his neighborhood.

A moment later, Harper's phone emitted a flash flood alert Thursday afternoon, but not one that effects the Elden area.

Such warnings were never a concern for Harper, or any other resident living off of Elden Lookout Road before the Museum Fire. However, now every one of them is keeping an eye on their phones in anticipation of a flooding alert.

In the aftermath of the Musuem Fire, the National Weather Service and Coconino County are warning Harper and his neighbors their community is directly in the path of the runoff caused by monsoon rains in the burned area to the north of Elden Lookout Road.

In response, county and city workers are already installing barriers to mitigate flooding for residents living off of Elden, and those living in Lockett Ranches, on Paradise and Grandview Drives and the Sunnyside neighborhood.

In Sunnyside, where water is likely to spread out, those short term efforts mostly take the form of sandbags. For Elden and Lockett Ranches, where there is a more distinct channel, short-term mitigation is largely taking the form of 20-foot long, 2,000-pound concrete jersey barriers.

"We cannot stop flooding. We can try to mitigate the flooding; mitigate the impacts of flooding, but we can't stop flooding because it's going to rain," said Lucinda Andreani, Coconino County Public Works Director.

Both the city of Flagstaff and the county have been working to model the severity of flooding in affected areas depending on the amount of rain storms may bring.

In those models, Coconino County engineer Christopher Tressler said they are being conservative, assuming the infrastructure in place may not work perfectly to dispose of flood waters. That's because past experience with post fire flooding has shown culverts and drainage systems often become inundated with debris, and are no longer able to let water pass, thus causing more flooding.

With the fire only about 12% contained, they are working with data that is liable to change. Nonetheless, preliminary models have shown levels of flooding may be fairly significant within all the affected areas with as little as an inch of rainfall in the burn area during a six-hour period.

However, the county does not expect any additional flooding risk in the Doney Park area despite the fire burning in that area's watershed.

Based on the current models, if two inches of rain falls on the burn area in a six-hour period, the wash running through areas near Elden Road and Lockett Ranches could see water levels 5-feet high, and laden with ash, sediment and debris.

That amount of rain could cause 4-feet of floodwaters in the channel that runs along Paradise Drive, and 1-foot deep flooding across large portions of the Sunnyside neighborhood.

According to county staff, those models are in line with a storm event that occurred on Tuesday afternoon and prompted the Weather Service to release a flood alert.

About half an inch of rain fell on the burn area in about an hour said Weather Service meteorologist Jonathan Suk.

While the rain caused little in the way of flooding, it did deposit half a foot of sediment on roads in the Elden and Lockett Ranches areas.

But that runoff was enough to make the threat of flooding a reality for many of the affected residents, including Bob Ogden who also lives off Elden Lookout Road.

Ogden, who worked as a wildland firefighter for 30 years before retiring, said he wasn't worried about the fire nearby and thus decided against following the orders to evacuate.

However, after Tuesday afternoon's monsoon storm left the wash less than 20 yards from Ogden's house flowing with a foot of black sediment laden water, he wondered if he had made the right choice.

"I looked around the corner of the garage and [the wash] was already ripping. It scared me," Ogden said. "I was standing here with a shovel going, '[expletive], I know nothing about this.' It was only like five minutes of rain."

But Ogden said he is ready. Four years ago, he purchased flood insurance in case of an event such as the Museum Fire.

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