As the Flagstaff City Council made the decision to continue working with the Army Corps of Engineers toward the completion of the Rio de Flag flood control project, community groups and some councilmembers have given attention to alternative and passed-over versions of the project.
Before the city and the Army Corps settled on the project’s current form, a feasibility study conducted in 2000 examined a number of other potential solutions to the issue of flooding. Included among them were the construction of levees that would turn the Thorpe Park ballfields into a lake in the case of a flood.
City engineer Rick Barrett, who has been working on the project for 15 years, said one idea examined in that report was to construct a system of 20-foot-tall levees from Frances Short Pond west to the Joe Montoya Senior Center where the natural topography would prevent water from escaping.
Levees would also have been built from the pond north into the neighborhood of Coconino Estates.
In that way, if a large flood occurred in Rio de Flag, the water would be stopped by the levees and instead flood the ballfields. Water could then be released slowly until the fields drain.
Barrett said the system could have reduced the amount of water flowing through the Rio by about three quarters, but was unpopular when presented to the public at the time.
Barrett said the city was cautioned by the Arizona Department of Water Resources about the possibility of the levees failing in if not properly maintained.
“If all of the sudden it failed, it would be worse than the 100-year flood that we’re trying to build this for,” Barrett said. “It would be terrible if all of that water broke loose at one point in time.”
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Nonetheless, that version of the project would have required less infrastructure downstream than the current project, Both versions, however, would return the Rio to its natural channel out of the Southside neighborhood.
Other alternatives the feasibility report examined included physically moving buildings out of the flood plain or working to flood-proof buildings within the plain, but both were deemed to be impractical and expensive.
The current project is designed to carry flood waters mostly in an underground culvert beginning just south of the pond and ending south of the railroad tracks. A six-block span of the Rio will have a system to let a smaller amount of water to still pass through the above-ground channel.
During the council meeting on Oct. 15, members of the community group Friends of the Rio de Flag asked council if the city could find a way to make the project work without putting flood waters into an underground culvert.
Council largely passed on the request, but Barrett said previous versions of the current project have kept the Rio open to the air.
To hold the amount of water brought by such a large flood, Barrett said the open channel was designed to be 80 to 95 feet wide, far wider than the current channel that is about 40 feet wide.
That would have led to the destruction of property, relocation of residents and the need for the city to buy lots of private property, something that was also unpopular among residents when originally proposed.