In August, Moab experienced record-breaking floods, capping off a vigorous monsoon season. The August floods caused enough damage to the city to declare a state of emergency. Since then, the city has actively assessed infrastructure damage.
City officials removed 120 tons of debris from a footbridge along 100 West, 180 tons from the Aggie Boulevard storm drain and reservoir, 60 tons from a bridge along 300 South, and 450 tons from a pond near the golf course. The staff calls it “Frog Pond”. The public works director still has hundreds of hours of work to do, according to Levi Jones. Already in the roads sector he has spent 930 hours and in the parks sector he has spent 400 hours clearing flood waters.
At the November 8 city council meeting, city engineer Chuck Williams provided an update on potential future flood mitigation projects. The real problem, Williams pointed out, is that the city of Moab is on a major drainage corridor. As the city grew, development encroached on the wetlands and marshes near the Colorado River that builders mostly avoided in the 1950s. According to the Federal Emergency Management floodplain map, most of the northern half of the city, from Mill Creek to where West 500 meets Route 191, will be flooded in his 500-year event.
Two streams, Mill Creek and Pack Creek, pass through the town on their way from the La Sal Mountains to the Colorado River. Within the city limits is the 6.2-mile Creek Corridor. Many of the city’s roads, utility pipes, and recreational areas (parks) pass over or through these corridors. When the creek overflows, floodwaters can wipe out major pieces of Moab’s infrastructure. This is what happened to him in August.
“When a flood occurs, damage occurs not only in the creek corridor, but also outside that corridor when the creek jumps over the creek bottom,” Williams said. “…here in Moab, we live in an eroding environment.”
The city has yet to hear from FEMA, the Federal Highway Administration, the Natural Resources Conservation Service, or an insurance trust for funding.
“When it comes to flood mitigation, or post-flood repairs, engineers and hydrologists go through this process of evaluating how to deal with it. It’s not one size fits all,” Williams says. Williams said there are three mitigation concepts the city can work on: take no action, take structural action, or take unstructured action.
The “do nothing” concept means the city will return the system to the state it was in just before the August floods. Williams said he expects the city to receive at least some funding, but if the city receives no funding at all, this would be the easiest concept to undertake. If it decides to go with this option, the city should at least seek to obtain an easement surrounding the town’s bridges to more easily stabilize the riverbanks when they inevitably flood. Yes, he added. If the land surrounding the bridge was privately owned, as it is today, city officials could work on it, but only with the owner’s permission, and the owner was on the city’s riverbank. is not responsible for stabilizing the
“Still, we only go 10 feet, not 100,” Williams said. “And it’s honestly not good enough.”
Williams also presented some potential structural changes. First, the city could replace the box culvert (building a bridge) at latitude 300 degrees south with a true bridge. Culverts were a problem during floods dating back to the 1970s. and across the road. Other modification ideas included installing a storm his drain from 300 S. to 100 W. below the creek. Maximize transport under road bridges by restoring channel depth to original elevation. Construction and maintenance of a series of upstream holding/wreckage pits.
One of Williams’ biggest ideas was to establish, build and manage the creek as a drainage system rather than a recreational and transportation system that would become a large undertaking. City officials must choose a design frequency of protection, such as protection against one-degree floods in 50 or 100 years, and build the waterway system accordingly.
Structural projects are never quick fixes. Many projects take at least several years to complete.
Ideas for nonstructural changes included implementing a real-time flood warning system, which Williams said would check the town’s USGS gauges during floods. proposed to establish and maintain vegetation along the road and to improve the city’s floodplain damage prevention ordinance. This includes raising the completed floor height of the new development to one foot above the 100-year base flood height.
The city council voted nothing during the meeting. Williams finally presented the idea as something the Corridor Drainage Master pondered to create his plan.
“Our recommendation is to continue this corridor drainage master planning work,” said City Manager Curly Castle. It takes into account our financial capacity, public involvement, recreational use, wastewater use, and transport use in the area. I can’t say. This is such a big problem that it takes a lot of time to plan and a lot of effort to execute. ”
