Current drainage infrastructure in downtown Springdale would not accommodate that "100-year, 24-hour FEMA flood," Brad Baldwin, the city's director of engineering, told the Springdale City Council on Tuesday night. Council members asked him to develop plans and return to the council with a cost for solving the problem.
The Federal Emergency Management Agency, through the Fayetteville firm FTN Associates, recently completed remapping all the creeks in Washington County and their floodplains and offered solutions.
"It's simple," Baldwin said. "Can we do anything to improve the Springdale flood plain? FTN says yes, we can."
The FTN report considered a series of three detention ponds built along Spring Creek to allow additional and controlled runoff along the creek's path. The best solution would be a pond built on property the city already owns along the northwest side of the Springdale Municipal Airport at a depth of 10 feet, 6 inches, Baldwin reported.
The bottleneck of draining storm water comes at the entrance of the box culvert taking the creek underground between East Emma Avenue and East Meadow Avenue. The detention pond would reduce the amount of water entering that culvert from 5,042 cubic feet per second to 4,644 cubic feet per second, the report shows.
The construction of the detention pond also would keep any flooding during that 100-year flood to within creek channel through downtown, essentially removing the floodplain.
"If you have a mapped floodplain, you have to buy flood insurance," which business owners will consider when choosing sites to develop, Baldwin said.
The pond would be built according to FAA guidance recommendations that "any on-airport storm water management facilities should allow a maximum 48-hour detention period for design storms," reads the report. "The ponds were designed with this requirement in mind; ponds are proposed to be kept empty and dry."
Dry ponds also allow city crews better conditions for mowing and maintaining the pond and don't attract waterfowl, said Mayor Doug Sprouse.
Baldwin said the pond could be engineered and designed by his department with the support of surveyors and draftsmen. The pond will require a lot of "dirt work" for construction, he said. "But it will make a big difference in the floodplain."
City Council members told Baldwin to move forward with design plans and return to the council with cost estimates.
More than 6 inches of rain deluged Northwest Arkansas and Springdale over a two-day span from April 29-30. Nine people died across Northwest Arkansas in the storms that caused flash flooding and knocked out power to thousands.
Turnbow Park, then under construction in downtown Springdale, became submerged as water drainage amounts into Spring Creek overwhelmed the box culvert which runs the creek underground. "Turnbow Park became its own detention pond," Baldwin said.
NW News on 12/05/2017