On Saturday, Aug. 20, Mill Creek flooded in what experts are calling a 100-year event. Mill Creek has flashed flooded multiple times during this year’s monsoon season, as recently as Aug. 11.
But Saturday’s flood was different. The flood water quickly overtook multiple bridges in town, distributing large debris like trees. It washed sand and mud onto the streets, into businesses, and across the Mill Creek parkway, wiping out guard rails. Preliminary data from the Mill Creek water gage near the Scott M. Matheson Wetlands Preserve shows the water height peaked at 15.65 feet—nearly 12 feet higher than usual.
On Sunday, the city and Grand County declared a state of emergency. The flood caused millions of dollars in city infrastructure damage: Nearly every building on Main Street, 100 West, and along the Mill Creek parkway was impacted, and the parkway itself is closed indefinitely due to debris and significant damage. Throughout the week, there was a notice to boil water for certain businesses, and some residents were without water for multiple days.
Now, the city has to rebuild. Staff are considering how to create better infrastructure to repair both the present damage and prepare for future monsoon seasons.
“That was the largest volume of water that I’ve seen,” City Engineer Chuck Williams said. He estimated that during its peak on Aug. 20, the creek was flowing at 5,000 cubic feet per second—the creek is usually flowing around 10 cfs.
Updates from the city
During a city council meeting on Aug. 23, Williams and Public Works Director Levi Jones provided an update on the city’s infrastructure.
Williams said he’s mostly concerned about the strength of the bridges. There are two creeks that cut through town—Mill Creek and Pack Creek—and within city limits, there are 11 transportation bridges, used for vehicles, and seven pedestrian bridges. During the flood on Aug. 11 and on Aug. 20, Mill Creek jumped out of the banks, causing lateral erosion.
“We dodged a bullet that we didn’t lose any bridges,” Williams said.
The ultimate damage—and what Williams sees as the initial breaking point for the city—happened when floodwaters overtopped the bridge on 300 S., which is near Up the Creek Campground and the dog park. The water managed to do this, Williams said, because debris from the flood quickly filled the underside of the bridge. The water then flowed three or four feet high over the bridge, which is how floodwater found its way to Main Street.
That bridge is the “lowest capacity bridge structure on Mill Creek,” he said. A flood insurance study for the city completed in 2009 predicted that in the case of a 50- or 100- year event, the bridge would be a liability.
The bridge on Main Street was also overtopped. The city doesn’t yet have exact measurements for the volume of water that was flowing: There are a number of gages installed along the creek, but the gages top out at 1,200 cfs, Williams said, and the water was flowing with more volume than that.
The city now has to consider what level of storm protection it wants: 10-year? 50-year? 100-year?; and how that would be achieved: a few options include channel widening, building larger bridges, or building an upstream detention basin. Williams also proposed that the city thinks about relocating the Mill Creek parkway to the top of the bank and suggested the city install a flood warning system.
Residential water was also a concern during this flood: On Aug. 20, many residents lost water completely or had low water pressure, and throughout the week, some still had no water. Williams said the city has waterlines that go under the creek, and typically, they’re buried so deep that even floods don’t impact them. But on Saturday, the water managed to scour the creek bed, causing damage to the waterlines—that’s another thing the city will have to deal with, he said.
“Every single piece of equipment we have is out at work,” Jones said. “Everybody’s operating.”
The Council didn’t make any long-term decisions during its meeting on Aug. 23; for now, crews are focused on getting streets and bridges cleaned up and safe. But councilmembers and staff agreed those decisions will have to be made sometime in the near future.
Mayor Joette Langianese said the city is focused on finding the funds to rebuild. In declaring a state of emergency, the city can access a number of funds and grants; she’s been in close contact with Gov. Spencer Cox.
“I’m confident that we have support from the governor’s office,” she said. “That was a big win—a bit of good news after everything we’ve been through.”
The city only has 15 days from the day of the event to submit information about infrastructure damage to the state; staff asked that residents who have interior damage to their home or business photograph and document the damage and email that information to the city at firstname.lastname@example.org. Anyone living outside of city limits in Grand County can submit damage reports at https://arcg.is/1nvm9e0. The number of damaged residences determines how much funding the city can receive from the Federal Emergency Management Agency.
“Please be vigilant, as we’re expecting more rain,” Castle said.
The city also formed four working groups: one to assess emergency response; one to work on a watercourse master plan; one dedicated to building assessments; and a communications and promotion group.
Castle and Langianese said they’re grateful for the support of Moab community members and state organizations during clean-up—the Utah Red Cross recently deployed trained disaster volunteers and staff to the area and provided 100 Red Cross flood clean-up kits to residents.
Moab “open for business”
Grand County, in a press release signed by the city and Chamber of Commerce, said Moab—its hotels, restaurants, retail shops, and trails—is still open for business while damage is being assessed and repaired.
“We are grateful for the support from many, including the Utah Office of Tourism, the Utah Tourism Industry Association, and the countless number of people who have voiced their concern and love for our community,” said August Granath, Grand County’s economic development director, in the release. “The best way to support Moab’s recovery is to come visit and support our local businesses. We are #MoabStrong, resilient, and open for business.”